fix: derivation references

Cargo.toml

@@ -4,3 +4,7 @@ members = [
     "nix-js",
     "nix-js-macros"
 ]
+
+[profile.profiling]
+inherits = "release"
+debug = true

Justfile

@@ -12,4 +12,4 @@
 
 [no-exit-message]
 @evalr expr:
-  RUST_LOG=info cargo run --bin eval --release -- '{{expr}}'
+  RUST_LOG=silent cargo run --bin eval --release -- '{{expr}}'

flake.nix

@@ -31,6 +31,7 @@
               valgrind
               hyperfine
               just
+              samply
 
               nodejs
               nodePackages.npm

nix-js-macros/src/ir.rs

@@ -92,6 +92,7 @@ pub fn ir_impl(input: TokenStream) -> TokenStream {
     let mut mut_variants = Vec::new();
     let mut as_ref_arms = Vec::new();
     let mut as_mut_arms = Vec::new();
+    let mut span_arms = Vec::new();
     let mut from_impls = Vec::new();
     let mut to_trait_impls = Vec::new();
 
@@ -112,6 +113,7 @@ pub fn ir_impl(input: TokenStream) -> TokenStream {
                 mut_variants.push(quote! { #name(&'a mut #inner_type) });
                 as_ref_arms.push(quote! { Self::#name(inner) => #ref_name::#name(inner) });
                 as_mut_arms.push(quote! { Self::#name(inner) => #mut_name::#name(inner) });
+                span_arms.push(quote! { Self::#name(inner) => inner.span });
                 from_impls.push(quote! {
                     impl From<#inner_type> for #base_name {
                         fn from(val: #inner_type) -> Self { #base_name::#name(val) }
@@ -140,6 +142,7 @@ pub fn ir_impl(input: TokenStream) -> TokenStream {
                 mut_variants.push(quote! { #name(&'a mut #inner_type) });
                 as_ref_arms.push(quote! { Self::#name(inner) => #ref_name::#name(inner) });
                 as_mut_arms.push(quote! { Self::#name(inner) => #mut_name::#name(inner) });
+                span_arms.push(quote! { Self::#name(inner) => inner.span });
                 from_impls.push(quote! {
                     impl From<#inner_type> for #base_name {
                         fn from(val: #inner_type) -> Self { #base_name::#name(val) }
@@ -172,6 +175,7 @@ pub fn ir_impl(input: TokenStream) -> TokenStream {
                 mut_variants.push(quote! { #name(&'a mut #inner_type) });
                 as_ref_arms.push(quote! { Self::#name(inner) => #ref_name::#name(inner) });
                 as_mut_arms.push(quote! { Self::#name(inner) => #mut_name::#name(inner) });
+                span_arms.push(quote! { Self::#name(inner) => inner.span });
                 from_impls.push(quote! {
                     impl From<#inner_type> for #base_name {
                         fn from(val: #inner_type) -> Self { #base_name::#name(val) }
@@ -223,6 +227,12 @@ pub fn ir_impl(input: TokenStream) -> TokenStream {
                     #( #as_mut_arms ),*
                 }
             }
+
+            pub fn span(&self) -> rnix::TextRange {
+                match self {
+                    #( #span_arms ),*
+                }
+            }
         }
 
         // `From` implementations for converting variant structs into the main enum.

nix-js/Cargo.toml

@@ -75,7 +75,7 @@ name = "builtins"
 harness = false
 
 [[bench]]
-name = "scc_optimization"
+name = "thunk_scope"
 harness = false
 
 [[bench]]

nix-js/runtime-ts/src/builtins/attrs.ts

@@ -31,7 +31,6 @@ export const hasAttr =
   (set: NixValue): boolean =>
     Object.hasOwn(forceAttrs(set), forceStringValue(s));
 
-let counter = 0;
 export const mapAttrs =
   (f: NixValue) =>
   (attrs: NixValue): NixAttrs => {
@@ -39,8 +38,7 @@ export const mapAttrs =
     const forcedF = forceFunction(f);
     const newAttrs: NixAttrs = {};
     for (const key in forcedAttrs) {
-      newAttrs[key] = createThunk(() => forceFunction(forcedF(key))(forcedAttrs[key]), `created by mapAttrs (${counter})`);
+      newAttrs[key] = createThunk(() => forceFunction(forcedF(key))(forcedAttrs[key]), "created by mapAttrs");
-      counter += 1;
     }
     return newAttrs;
   };

nix-js/runtime-ts/src/builtins/derivation.ts

@@ -46,7 +46,7 @@ const validateBuilder = (attrs: NixAttrs, outContext: NixStringContext): string
   if (!("builder" in attrs)) {
     throw new Error("derivation: missing required attribute 'builder'");
   }
-  return coerceToString(attrs.builder, StringCoercionMode.ToString, false, outContext);
+  return coerceToString(attrs.builder, StringCoercionMode.ToString, true, outContext);
 };
 
 const validateSystem = (attrs: NixAttrs): string => {
@@ -87,17 +87,18 @@ const extractArgs = (attrs: NixAttrs, outContext: NixStringContext): string[] =>
     return [];
   }
   const argsList = forceList(attrs.args);
-  return argsList.map((a) => coerceToString(a, StringCoercionMode.ToString, false, outContext));
+  return argsList.map((a) => coerceToString(a, StringCoercionMode.ToString, true, outContext));
 };
 
-const extractEnv = (
+const structuredAttrsExcludedKeys = new Set([
-  attrs: NixAttrs,
+  "__structuredAttrs",
-  structuredAttrs: boolean,
+  "__ignoreNulls",
-  ignoreNulls: boolean,
+  "__contentAddressed",
-  outContext: NixStringContext,
+  "impure",
-  drvName: string,
+  "args",
-): Map<string, string> => {
+]);
-  const specialAttrs = new Set([
+
+const specialAttrs = new Set([
   "name",
   "builder",
   "system",
@@ -107,14 +108,30 @@ const extractEnv = (
   "__ignoreNulls",
   "__contentAddressed",
   "impure",
-  ]);
+]);
 
+const sortedJsonStringify = (obj: Record<string, any>): string => {
+  const sortedKeys = Object.keys(obj).sort();
+  const sortedObj: Record<string, any> = {};
+  for (const key of sortedKeys) {
+    sortedObj[key] = obj[key];
+  }
+  return JSON.stringify(sortedObj);
+};
+
+const extractEnv = (
+  attrs: NixAttrs,
+  structuredAttrs: boolean,
+  ignoreNulls: boolean,
+  outContext: NixStringContext,
+  drvName: string,
+): Map<string, string> => {
   const env = new Map<string, string>();
 
   if (structuredAttrs) {
     const jsonAttrs: Record<string, any> = {};
     for (const [key, value] of Object.entries(attrs)) {
-      if (!specialAttrs.has(key)) {
+      if (!structuredAttrsExcludedKeys.has(key)) {
         const forcedValue = force(value);
         if (ignoreNulls && forcedValue === null) {
           continue;
@@ -165,7 +182,7 @@ const extractEnv = (
         );
       }
     }
-    env.set("__json", JSON.stringify(jsonAttrs));
+    env.set("__json", sortedJsonStringify(jsonAttrs));
   } else {
     for (const [key, value] of Object.entries(attrs)) {
       if (!specialAttrs.has(key)) {
@@ -173,7 +190,7 @@ const extractEnv = (
         if (ignoreNulls && forcedValue === null) {
           continue;
         }
-        env.set(key, coerceToString(value, StringCoercionMode.ToString, false, outContext));
+        env.set(key, coerceToString(value, StringCoercionMode.ToString, true, outContext));
       }
     }
   }
@@ -187,14 +204,32 @@ interface FixedOutputInfo {
   hashMode: string;
 }
 
-const extractFixedOutputInfo = (attrs: NixAttrs): FixedOutputInfo | null => {
+const extractFixedOutputInfo = (attrs: NixAttrs, ignoreNulls: boolean): FixedOutputInfo | null => {
   if (!("outputHash" in attrs)) {
     return null;
   }
 
+  const hashValue = force(attrs.outputHash);
+  if (ignoreNulls && hashValue === null) {
+    return null;
+  }
   const hash = forceStringValue(attrs.outputHash);
-  const hashAlgo = "outputHashAlgo" in attrs ? forceStringValue(attrs.outputHashAlgo) : "sha256";
+
-  const hashMode = "outputHashMode" in attrs ? forceStringValue(attrs.outputHashMode) : "flat";
+  let hashAlgo = "sha256";
+  if ("outputHashAlgo" in attrs) {
+    const algoValue = force(attrs.outputHashAlgo);
+    if (!(ignoreNulls && algoValue === null)) {
+      hashAlgo = forceStringValue(attrs.outputHashAlgo);
+    }
+  }
+
+  let hashMode = "flat";
+  if ("outputHashMode" in attrs) {
+    const modeValue = force(attrs.outputHashMode);
+    if (!(ignoreNulls && modeValue === null)) {
+      hashMode = forceStringValue(attrs.outputHashMode);
+    }
+  }
 
   if (hashMode !== "flat" && hashMode !== "recursive") {
     throw new Error(`derivation: invalid outputHashMode '${hashMode}' (must be 'flat' or 'recursive')`);
@@ -217,14 +252,13 @@ export const derivationStrict = (args: NixValue): NixAttrs => {
   const builder = validateBuilder(attrs, collectedContext);
   const platform = validateSystem(attrs);
 
-  const outputs = extractOutputs(attrs);
-  const fixedOutputInfo = extractFixedOutputInfo(attrs);
-  validateFixedOutputConstraints(fixedOutputInfo, outputs);
-
   const structuredAttrs = "__structuredAttrs" in attrs ? force(attrs.__structuredAttrs) === true : false;
-
   const ignoreNulls = "__ignoreNulls" in attrs ? force(attrs.__ignoreNulls) === true : false;
 
+  const outputs = extractOutputs(attrs);
+  const fixedOutputInfo = extractFixedOutputInfo(attrs, ignoreNulls);
+  validateFixedOutputConstraints(fixedOutputInfo, outputs);
+
   if ("__contentAddressed" in attrs && force(attrs.__contentAddressed) === true) {
     throw new Error("ca derivations are not supported");
   }
@@ -236,15 +270,28 @@ export const derivationStrict = (args: NixValue): NixAttrs => {
   const drvArgs = extractArgs(attrs, collectedContext);
   const env = extractEnv(attrs, structuredAttrs, ignoreNulls, collectedContext, drvName);
 
+  if (!structuredAttrs) {
     env.set("name", drvName);
     env.set("builder", builder);
     env.set("system", platform);
     if (outputs.length > 1 || outputs[0] !== "out") {
       env.set("outputs", outputs.join(" "));
     }
+  }
 
   const { inputDrvs, inputSrcs } = extractInputDrvsAndSrcs(collectedContext);
 
+  const collectDrvReferences = (): string[] => {
+    const refs = new Set<string>();
+    for (const src of inputSrcs) {
+      refs.add(src);
+    }
+    for (const drvPath of inputDrvs.keys()) {
+      refs.add(drvPath);
+    }
+    return Array.from(refs).sort();
+  };
+
   let outputInfos: Map<string, OutputInfo>;
   let drvPath: string;
 
@@ -282,7 +329,7 @@ export const derivationStrict = (args: NixValue): NixAttrs => {
     };
     const finalAterm = generateAterm(finalDrv);
     const finalDrvHash = Deno.core.ops.op_sha256_hex(finalAterm);
-    drvPath = Deno.core.ops.op_make_store_path("text", finalDrvHash, `${drvName}.drv`);
+    drvPath = Deno.core.ops.op_make_text_store_path(finalDrvHash, `${drvName}.drv`, collectDrvReferences());
   } else {
     const maskedOutputs = new Map<string, OutputInfo>(
       outputs.map((o) => [
@@ -333,7 +380,7 @@ export const derivationStrict = (args: NixValue): NixAttrs => {
     const finalAterm = generateAterm(finalDrv);
     const finalDrvHash = Deno.core.ops.op_sha256_hex(finalAterm);
 
-    drvPath = Deno.core.ops.op_make_store_path("text", finalDrvHash, `${drvName}.drv`);
+    drvPath = Deno.core.ops.op_make_text_store_path(finalDrvHash, `${drvName}.drv`, collectDrvReferences());
   }
 
   const result: NixAttrs = {};
@@ -353,77 +400,52 @@ export const derivationStrict = (args: NixValue): NixAttrs => {
 
 export const derivation = (args: NixValue): NixAttrs => {
   const attrs = forceAttrs(args);
-  const strict = derivationStrict(args);
 
   const outputs: string[] = extractOutputs(attrs);
-  const drvName = validateName(attrs);
-  const collectedContext: NixStringContext = new Set();
-  const builder = validateBuilder(attrs, collectedContext);
-  const platform = validateSystem(attrs);
-  const structuredAttrs = "__structuredAttrs" in attrs ? force(attrs.__structuredAttrs) === true : false;
-  const ignoreNulls = "__ignoreNulls" in attrs ? force(attrs.__ignoreNulls) === true : false;
-  const drvArgs = extractArgs(attrs, collectedContext);
 
-  const specialAttrs = new Set([
+  const strictThunk = createThunk(() => derivationStrict(args), "derivationStrict");
-    "name",
-    "builder",
-    "system",
-    "args",
-    "outputs",
-    "__structuredAttrs",
-    "__ignoreNulls",
-    "__contentAddressed",
-    "impure",
-  ]);
 
-  const baseAttrs: NixAttrs = {
+  const commonAttrs: NixAttrs = { ...attrs };
+
+  const outputToAttrListElement = (outputName: string): { name: string; value: NixAttrs } => {
+    const value: NixAttrs = {
+      ...commonAttrs,
+      outPath: createThunk(() => (force(strictThunk) as NixAttrs)[outputName], `outPath_${outputName}`),
+      drvPath: createThunk(() => (force(strictThunk) as NixAttrs).drvPath, "drvPath"),
       type: "derivation",
-    drvPath: strict.drvPath,
-    name: drvName,
-    builder,
-    system: platform,
-  };
-
-  if (drvArgs.length > 0) {
-    baseAttrs.args = drvArgs;
-  }
-
-  if (!structuredAttrs) {
-    for (const [key, value] of Object.entries(attrs)) {
-      if (!specialAttrs.has(key) && !outputs.includes(key)) {
-        const forcedValue = force(value);
-        if (!(ignoreNulls && forcedValue === null)) {
-          baseAttrs[key] = value;
-        }
-      }
-    }
-  }
-
-  const outputsList: NixAttrs[] = [];
-
-  for (const outputName of outputs) {
-    const outputObj: NixAttrs = {
-      ...baseAttrs,
-      outPath: strict[outputName],
       outputName,
     };
-    outputsList.push(outputObj);
+    return { name: outputName, value };
-  }
+  };
 
-  baseAttrs.drvAttrs = attrs;
+  const outputsList = outputs.map(outputToAttrListElement);
-  for (const [i, outputName] of outputs.entries()) {
-    baseAttrs[outputName] = createThunk(() => outputsList[i], `output_${outputName}`);
-  }
-  baseAttrs.all = createThunk(() => outputsList, "all_outputs");
 
-  for (const outputObj of outputsList) {
+  for (const { name: outputName } of outputsList) {
+    commonAttrs[outputName] = createThunk(
+      () => outputsList.find((o) => o.name === outputName)!.value,
+      `output_${outputName}`,
+    );
+  }
+  commonAttrs.all = createThunk(
+    () => outputsList.map((o) => o.value),
+    "all_outputs",
+  );
+  commonAttrs.drvAttrs = attrs;
+
+  for (const { value: outputObj } of outputsList) {
+    for (const { name: outputName } of outputsList) {
+      outputObj[outputName] = createThunk(
+        () => outputsList.find((o) => o.name === outputName)!.value,
+        `output_${outputName}`,
+      );
+    }
+    outputObj.all = createThunk(
+      () => outputsList.map((o) => o.value),
+      "all_outputs",
+    );
     outputObj.drvAttrs = attrs;
-    for (const [i, outputName] of outputs.entries()) {
-      outputObj[outputName] = createThunk(() => outputsList[i], `output_${outputName}`);
-    }
-    outputObj.all = createThunk(() => outputsList, "all_outputs");
   }
 
-  return outputsList[0];
+  return outputsList[0].value;
 };
 

nix-js/runtime-ts/src/builtins/functional.ts

@@ -5,6 +5,7 @@
 import { CatchableError, HAS_CONTEXT, type NixValue } from "../types";
 import { force } from "../thunk";
 import { coerceToString, StringCoercionMode } from "./conversion";
+import { printValue } from "../print";
 
 export const seq =
   (e1: NixValue) =>
@@ -40,7 +41,7 @@ export const throwFunc = (s: NixValue): never => {
 export const trace =
   (e1: NixValue) =>
   (e2: NixValue): NixValue => {
-    console.log(`trace: ${coerceToString(e1, StringCoercionMode.Base)}`);
+    console.error(`trace: ${printValue(e1)}`);
     return e2;
   };
 

nix-js/runtime-ts/src/builtins/index.ts

@@ -18,7 +18,8 @@ import * as misc from "./misc";
 import * as derivation from "./derivation";
 
 import type { NixValue } from "../types";
-import { createThunk, force } from "../thunk";
+import { createThunk, force, isThunk } from "../thunk";
+import { getTos } from "../helpers";
 
 /**
  * Symbol used to mark functions as primops (primitive operations)
@@ -263,4 +264,9 @@ export const builtins: any = {
   nixPath: [],
   nixVersion: "2.31.2",
   storeDir: "INVALID_PATH",
+
+  __traceCaller: (e: NixValue) => {
+    console.log(`traceCaller: ${getTos()}`)
+    return e
+  },
 };

nix-js/runtime-ts/src/builtins/io.ts

@@ -3,7 +3,7 @@
  * Implemented via Rust ops exposed through deno_core
  */
 
-import { forceAttrs, forceBool, forceList, forceStringNoCtx, forceStringValue } from "../type-assert";
+import { forceAttrs, forceBool, forceFunction, forceList, forceStringNoCtx, forceStringValue } from "../type-assert";
 import type { NixValue, NixAttrs, NixPath } from "../types";
 import { isNixPath, IS_PATH, CatchableError } from "../types";
 import { force } from "../thunk";
@@ -12,7 +12,8 @@ import { getPathValue } from "../path";
 import type { NixStringContext, StringWithContext } from "../string-context";
 import { mkStringWithContext } from "../string-context";
 import { isPath } from "./type-check";
-import { getCorepkg } from "../corepkgs";
+
+const importCache = new Map<string, NixValue>();
 
 export const importFunc = (path: NixValue): NixValue => {
   const context: NixStringContext = new Set();
@@ -30,9 +31,17 @@ Dependency tracking for imported derivations may be incomplete.`,
     );
   }
 
+  const cached = importCache.get(pathStr);
+  if (cached !== undefined) {
+    return cached;
+  }
+
   // Call Rust op - returns JS code string
   const code = Deno.core.ops.op_import(pathStr);
-  return Function(`return (${code})`)();
+  const result = Function(`return (${code})`)();
+
+  importCache.set(pathStr, result);
+  return result;
 };
 
 export const scopedImport =
@@ -324,7 +333,7 @@ export const pathExists = (path: NixValue): boolean => {
  * Parameters (attribute set):
  * - path (required): Path to add to the store
  * - name (optional): Name to use in store path (defaults to basename)
- * - filter (optional): Function (path, type) -> bool (NOT IMPLEMENTED YET)
+ * - filter (optional): Function (path, type) -> bool
  * - recursive (optional): Boolean, default true (NAR vs flat hashing)
  * - sha256 (optional): Expected SHA-256 hash (hex-encoded)
  *
@@ -357,9 +366,30 @@ export const path = (args: NixValue): string => {
   // Optional: sha256 parameter
   const sha256 = "sha256" in attrs ? forceStringValue(attrs.sha256) : null;
 
-  // TODO: Handle filter parameter
+  // Handle filter parameter
   if ("filter" in attrs) {
-    throw new Error("builtins.path: 'filter' parameter is not yet implemented");
+    const filterFn = forceFunction(attrs.filter);
+
+    const entries: [string, string][] = Deno.core.ops.op_walk_dir(pathStr);
+
+    const includePaths: string[] = [];
+    for (const [relPath, fileType] of entries) {
+      const fullPath = pathStr + "/" + relPath;
+      const innerFn = forceFunction(filterFn(fullPath));
+      const shouldInclude = force(innerFn(fileType));
+      if (shouldInclude === true) {
+        includePaths.push(relPath);
+      }
+    }
+
+    const storePath: string = Deno.core.ops.op_add_filtered_path(
+      pathStr,
+      name,
+      recursive,
+      sha256,
+      includePaths,
+    );
+    return storePath;
   }
 
   // Call Rust op to add path to store
@@ -452,13 +482,8 @@ export const findFile =
     }
 
     if (lookupPathStr.startsWith("nix/")) {
-      const corepkgName = lookupPathStr.substring(4);
-      const corepkgContent = getCorepkg(corepkgName);
-
-      if (corepkgContent !== undefined) {
       // FIXME: special path type
-        return { [IS_PATH]: true, value: `<nix/${corepkgName}>` };
+      return { [IS_PATH]: true, value: `<${lookupPathStr}>` };
-      }
     }
 
     throw new CatchableError(`file '${lookupPathStr}' was not found in the Nix search path`);

nix-js/runtime-ts/src/builtins/list.ts

@@ -141,10 +141,9 @@ export const all =
 export const any =
   (pred: NixValue) =>
   (list: NixValue): boolean => {
-    const forcedList = forceList(list);
+    // CppNix forces `pred` eagerly
-    if (forcedList.length) {
     const f = forceFunction(pred);
+    const forcedList = forceList(list);
+    // `false` when no element
     return forcedList.some((e) => forceBool(f(e)));
-    }
-    return true;
   };

nix-js/runtime-ts/src/builtins/misc.ts

@@ -2,8 +2,8 @@
  * Miscellaneous builtin functions
  */
 
-import { createThunk, force } from "../thunk";
+import { force } from "../thunk";
-import { CatchableError } from "../types";
+import { CatchableError, ATTR_POSITIONS } from "../types";
 import type { NixAttrs, NixBool, NixStrictValue, NixValue } from "../types";
 import { forceList, forceAttrs, forceFunction, forceStringValue, forceString, forceStringNoCtx } from "../type-assert";
 import * as context from "./context";
@@ -20,7 +20,8 @@ import {
 export const addErrorContext =
   (e1: NixValue) =>
   (e2: NixValue): NixValue => {
-    console.log("[WARNING]: addErrorContext not implemented");
+    // FIXME:
+    // console.log("[WARNING]: addErrorContext not implemented");
     return e2;
   };
 
@@ -164,6 +165,14 @@ export const functionArgs = (f: NixValue): NixAttrs => {
     for (const key of func.args!.optional) {
       ret[key] = true;
     }
+    const positions = func.args!.positions;
+    if (positions && Object.keys(positions).length > 0) {
+      Object.defineProperty(ret, ATTR_POSITIONS, {
+        value: positions,
+        enumerable: false,
+        writable: false,
+      });
+    }
     return ret;
   }
   return {};
@@ -253,8 +262,9 @@ export const parseFlakeRef = (s: NixValue): never => {
   throw new Error("Not implemented: parseFlakeRef");
 };
 
-export const placeholder = (output: NixValue): never => {
+export const placeholder = (output: NixValue): NixValue => {
-  throw new Error("Not implemented: placeholder");
+  const outputStr = forceStringNoCtx(output);
+  return Deno.core.ops.op_make_placeholder(outputStr);
 };
 
 export const replaceStrings =

nix-js/runtime-ts/src/conversion.ts

@@ -1,6 +1,7 @@
 import { HAS_CONTEXT, NixStringContext } from "./string-context";
 import { force } from "./thunk";
 import type { NixValue } from "./types";
+import { isStringWithContext } from "./types";
 
 export const nixValueToJson = (
   value: NixValue,
@@ -35,7 +36,6 @@ export const nixValueToJson = (
     if (seen.has(v)) {
       throw new Error("derivation: circular reference detected in __structuredAttrs");
     }
-    // FIXME: tryAttrsToString
     seen.add(v);
   }
 
@@ -44,9 +44,31 @@ export const nixValueToJson = (
   }
 
   if (typeof v === "object") {
+    if ("__toString" in v && typeof force(v.__toString) === "function") {
+      const toStringMethod = force(v.__toString) as (self: typeof v) => NixValue;
+      const result = force(toStringMethod(v));
+      if (typeof result === "string") {
+        return result;
+      }
+      if (isStringWithContext(result)) {
+        if (outContext) {
+          for (const elem of result.context) {
+            outContext.add(elem);
+          }
+        }
+        return result.value;
+      }
+      return nixValueToJson(result, seen, outContext);
+    }
+
+    if ("outPath" in v) {
+      return nixValueToJson(v.outPath, seen, outContext);
+    }
+
     const result: Record<string, any> = {};
-    for (const [key, val] of Object.entries(v)) {
+    const keys = Object.keys(v).sort();
-      result[key] = nixValueToJson(val, seen, outContext);
+    for (const key of keys) {
+      result[key] = nixValueToJson((v as Record<string, NixValue>)[key], seen, outContext);
     }
     return result;
   }

nix-js/runtime-ts/src/corepkgs/fetchurl.nix.ts

@@ -1,73 +0,0 @@
-export const FETCHURL_NIX = `{
-  system ? "", # obsolete
-  url,
-  hash ? "", # an SRI hash
-
-  # Legacy hash specification
-  md5 ? "",
-  sha1 ? "",
-  sha256 ? "",
-  sha512 ? "",
-  outputHash ?
-    if hash != "" then
-      hash
-    else if sha512 != "" then
-      sha512
-    else if sha1 != "" then
-      sha1
-    else if md5 != "" then
-      md5
-    else
-      sha256,
-  outputHashAlgo ?
-    if hash != "" then
-      ""
-    else if sha512 != "" then
-      "sha512"
-    else if sha1 != "" then
-      "sha1"
-    else if md5 != "" then
-      "md5"
-    else
-      "sha256",
-
-  executable ? false,
-  unpack ? false,
-  name ? baseNameOf (toString url),
-  impure ? false,
-}:
-
-derivation (
-  {
-    builder = "builtin:fetchurl";
-
-    # New-style output content requirements.
-    outputHashMode = if unpack || executable then "recursive" else "flat";
-
-    inherit
-      name
-      url
-      executable
-      unpack
-      ;
-
-    system = "builtin";
-
-    # No need to double the amount of network traffic
-    preferLocalBuild = true;
-
-    # This attribute does nothing; it's here to avoid changing evaluation results.
-    impureEnvVars = [
-      "http_proxy"
-      "https_proxy"
-      "ftp_proxy"
-      "all_proxy"
-      "no_proxy"
-    ];
-
-    # To make "nix-prefetch-url" work.
-    urls = [ url ];
-  }
-  // (if impure then { __impure = true; } else { inherit outputHashAlgo outputHash; })
-)
-`;

nix-js/runtime-ts/src/corepkgs/index.ts

@@ -1,9 +0,0 @@
-import { FETCHURL_NIX } from "./fetchurl.nix";
-
-export const COREPKGS: Record<string, string> = {
-  "fetchurl.nix": FETCHURL_NIX,
-};
-
-export const getCorepkg = (name: string): string | undefined => {
-  return COREPKGS[name];
-};

nix-js/runtime-ts/src/helpers.ts

@@ -19,12 +19,10 @@ interface StackFrame {
 const callStack: StackFrame[] = [];
 const MAX_STACK_DEPTH = 1000;
 
-export const STACK_TRACE = { enabled: false };
-
 function enrichError(error: unknown): Error {
   const err = error instanceof Error ? error : new Error(String(error));
 
-  if (!STACK_TRACE.enabled || callStack.length === 0) {
+  if (callStack.length === 0) {
     return err;
   }
 
@@ -38,13 +36,17 @@ function enrichError(error: unknown): Error {
   return err;
 }
 
+export const getTos = (): string => {
+  const tos = callStack[callStack.length - 2];
+  const { file, line, column } = Deno.core.ops.op_decode_span(tos.span);
+  return `${tos.message} at ${file}:${line}:${column}`;
+}
+
 /**
  * Push an error context onto the stack
  * Used for tracking evaluation context (e.g., "while evaluating the condition")
  */
 export const pushContext = (message: string, span: string): void => {
-  if (!STACK_TRACE.enabled) return;
-
   if (callStack.length >= MAX_STACK_DEPTH) {
     callStack.shift();
   }
@@ -55,7 +57,6 @@ export const pushContext = (message: string, span: string): void => {
  * Pop an error context from the stack
  */
 export const popContext = (): void => {
-  if (!STACK_TRACE.enabled) return;
   callStack.pop();
 };
 
@@ -64,10 +65,6 @@ export const popContext = (): void => {
  * Automatically pushes context before execution and pops after
  */
 export const withContext = <T>(message: string, span: string, fn: () => T): T => {
-  if (!STACK_TRACE.enabled) {
-    return fn();
-  }
-
   pushContext(message, span);
   try {
     return fn();
@@ -87,23 +84,20 @@ export const withContext = <T>(message: string, span: string, fn: () => T): T =>
  * - Path mode: Store contexts are forbidden (will throw error)
  * - String mode: All contexts are preserved and merged
  *
- * If first element is a path, result is a path (with constraint: no store context allowed)
- *
  * @param parts - Array of values to concatenate
+ * @param forceString - If true, result is always a string (paths are copied to store)
  * @returns String or Path with merged contexts from all parts
  */
-export const concatStringsWithContext = (parts: NixValue[]): NixString | NixPath => {
+export const concatStringsWithContext = (parts: NixValue[], forceString: boolean): NixString | NixPath => {
   if (parts.length === 0) {
     return "";
   }
 
   const forced = parts.map(force);
 
-  // Check if first element is a path
+  const firstIsPath = !forceString && isNixPath(forced[0]);
-  const firstIsPath = isNixPath(forced[0]);
 
   if (firstIsPath) {
-    // Path concatenation mode: result will be a path
     let result = (forced[0] as NixPath).value;
 
     for (let i = 1; i < forced.length; i++) {
@@ -114,13 +108,11 @@ export const concatStringsWithContext = (parts: NixValue[]): NixString | NixPath
       } else if (typeof part === "string") {
         result += part;
       } else if (isStringWithContext(part)) {
-        // Lix constraint: cannot mix store context with paths
         if (part.context.size > 0) {
           throw new TypeError("a string that refers to a store path cannot be appended to a path");
         }
         result += part.value;
       } else {
-        // Coerce to string
         const tempContext: NixStringContext = new Set();
         const coerced = coerceToString(part, StringCoercionMode.Interpolation, false, tempContext);
 
@@ -135,19 +127,15 @@ export const concatStringsWithContext = (parts: NixValue[]): NixString | NixPath
     return mkPath(result);
   }
 
-  // String concatenation mode
-  // Note: firstIsPath is already false at this point, otherwise we would have
-  // returned in the path concatenation branch above
   const context: NixStringContext = new Set();
   const strParts: string[] = [];
 
-  for (const part of parts) {
+  for (const part of forced) {
-    const forced = force(part);
+    if (isNixPath(part)) {
-    if (isNixPath(forced)) {
+      const str = coerceToString(part, StringCoercionMode.Interpolation, true, context);
-      const str = coerceToString(forced, StringCoercionMode.Interpolation, true, context);
       strParts.push(str);
     } else {
-      const str = coerceToString(forced, StringCoercionMode.Interpolation, false, context);
+      const str = coerceToString(part, StringCoercionMode.Interpolation, false, context);
       strParts.push(str);
     }
   }
@@ -183,7 +171,7 @@ export const resolvePath = (currentDir: string, path: NixValue): NixPath => {
 };
 
 export const select = (obj: NixValue, attrpath: NixValue[], span?: string): NixValue => {
-  if (STACK_TRACE.enabled && span) {
+  if (span) {
     const pathStrings = attrpath.map((a) => forceStringValue(a));
     const path = pathStrings.join(".");
     const message = path ? `while selecting attribute [${path}]` : "while selecting attribute";
@@ -229,7 +217,7 @@ export const selectWithDefault = (
   default_val: NixValue,
   span?: string,
 ): NixValue => {
-  if (STACK_TRACE.enabled && span) {
+  if (span) {
     const pathStrings = attrpath.map((a) => forceStringValue(a));
     const path = pathStrings.join(".");
     const message = path ? `while selecting attribute [${path}]` : "while selecting attribute";
@@ -337,7 +325,7 @@ export const validateParams = (
 };
 
 export const call = (func: NixValue, arg: NixValue, span?: string): NixValue => {
-  if (STACK_TRACE.enabled && span) {
+  if (span) {
     if (callStack.length >= MAX_STACK_DEPTH) {
       callStack.shift();
     }

nix-js/runtime-ts/src/index.ts

@@ -4,7 +4,7 @@
  * All functionality is exported via the global `Nix` object
  */
 
-import { createThunk, force, isThunk, IS_THUNK, DEBUG_THUNKS } from "./thunk";
+import { createThunk, force, isThunk, IS_THUNK, DEBUG_THUNKS, forceDeepSafe, IS_CYCLE } from "./thunk";
 import {
   select,
   selectWithDefault,
@@ -14,7 +14,6 @@ import {
   concatStringsWithContext,
   call,
   assert,
-  STACK_TRACE,
   pushContext,
   popContext,
   withContext,
@@ -35,13 +34,14 @@ export type NixRuntime = typeof Nix;
 export const Nix = {
   createThunk,
   force,
+  forceDeepSafe,
   forceBool,
   isThunk,
   IS_THUNK,
+  IS_CYCLE,
   HAS_CONTEXT,
   IS_PATH,
   DEBUG_THUNKS,
-  STACK_TRACE,
 
   assert,
   call,

nix-js/runtime-ts/src/operators.ts

@@ -224,15 +224,17 @@ export const op = {
       const attrsA = av as NixAttrs;
       const attrsB = bv as NixAttrs;
 
-      // If both denote a derivation (type = "derivation"), compare their outPaths
+      // Derivation comparison: compare outPaths only
-      const isDerivationA = "type" in attrsA && force(attrsA.type) === "derivation";
+      // Safe to force 'type' because it's always a string literal, never a computed value
-      const isDerivationB = "type" in attrsB && force(attrsB.type) === "derivation";
+      if ("type" in attrsA && "type" in attrsB) {
-
+        const typeValA = force(attrsA.type);
-      if (isDerivationA && isDerivationB) {
+        const typeValB = force(attrsB.type);
+        if (typeValA === "derivation" && typeValB === "derivation") {
           if ("outPath" in attrsA && "outPath" in attrsB) {
             return op.eq(attrsA.outPath, attrsB.outPath);
           }
         }
+      }
 
       // Otherwise, compare attributes one by one
       const keysA = Object.keys(attrsA).sort();

nix-js/runtime-ts/src/path.ts

@@ -1,7 +1,38 @@
 import { IS_PATH, type NixPath } from "./types";
 
+const canonicalizePath = (path: string): string => {
+  const parts: string[] = [];
+  let i = 0;
+  const len = path.length;
+
+  while (i < len) {
+    while (i < len && path[i] === "/") i++;
+    if (i >= len) break;
+
+    let j = i;
+    while (j < len && path[j] !== "/") j++;
+    const component = path.slice(i, j);
+    i = j;
+
+    if (component === ".") {
+      continue;
+    } else if (component === "..") {
+      if (parts.length > 0) {
+        parts.pop();
+      }
+    } else {
+      parts.push(component);
+    }
+  }
+
+  if (parts.length === 0) {
+    return "/";
+  }
+  return "/" + parts.join("/");
+};
+
 export const mkPath = (value: string): NixPath => {
-  return { [IS_PATH]: true, value };
+  return { [IS_PATH]: true, value: canonicalizePath(value) };
 };
 
 export const getPathValue = (p: NixPath): string => {

nix-js/runtime-ts/src/print.ts

@@ -0,0 +1,107 @@
+import { isThunk, IS_CYCLE } from "./thunk";
+import { isStringWithContext } from "./string-context";
+import { isNixPath, type NixValue } from "./types";
+import { is_primop, get_primop_metadata } from "./builtins/index";
+
+export const printValue = (value: NixValue, seen: WeakSet<object> = new WeakSet()): string => {
+  if (isThunk(value)) {
+    return "«thunk»";
+  }
+
+  if (value === null) {
+    return "null";
+  }
+
+  if (typeof value === "boolean") {
+    return value ? "true" : "false";
+  }
+
+  if (typeof value === "bigint") {
+    return value.toString();
+  }
+
+  if (typeof value === "number") {
+    return value.toString();
+  }
+
+  if (typeof value === "string") {
+    return printString(value);
+  }
+
+  if (typeof value === "function") {
+    if (is_primop(value)) {
+      const meta = get_primop_metadata(value);
+      if (meta && meta.applied > 0) {
+        return "<PRIMOP-APP>";
+      }
+      return "<PRIMOP>";
+    }
+    return "<LAMBDA>";
+  }
+
+  if (typeof value === "object") {
+    if (IS_CYCLE in value && (value as any)[IS_CYCLE] === true) {
+      return "«repeated»";
+    }
+
+    if (seen.has(value)) {
+      return "«repeated»";
+    }
+    seen.add(value);
+
+    if (isNixPath(value)) {
+      return value.value;
+    }
+
+    if (isStringWithContext(value)) {
+      return printString(value.value);
+    }
+
+    if (Array.isArray(value)) {
+      const items = value.map((v) => printValue(v, seen)).join(" ");
+      return `[ ${items} ]`;
+    }
+
+    const entries = Object.entries(value)
+      .map(([k, v]) => `${printSymbol(k)} = ${printValue(v, seen)};`)
+      .join(" ");
+    return `{${entries ? ` ${entries} ` : " "}}`;
+  }
+
+  return "<unknown>";
+};
+
+const printString = (s: string): string => {
+  let result = '"';
+  for (const c of s) {
+    switch (c) {
+      case "\\":
+        result += "\\\\";
+        break;
+      case '"':
+        result += '\\"';
+        break;
+      case "\n":
+        result += "\\n";
+        break;
+      case "\r":
+        result += "\\r";
+        break;
+      case "\t":
+        result += "\\t";
+        break;
+      default:
+        result += c;
+    }
+  }
+  return result + '"';
+};
+
+const SYMBOL_REGEX = /^[a-zA-Z_][a-zA-Z0-9_'-]*$/;
+
+const printSymbol = (s: string): string => {
+  if (SYMBOL_REGEX.test(s)) {
+    return s;
+  }
+  return printString(s);
+};

nix-js/runtime-ts/src/string-context.ts

@@ -165,6 +165,10 @@ export const parseContextToInfoMap = (context: NixStringContext): Map<string, Pa
     }
   }
 
+  for (const info of result.values()) {
+    info.outputs.sort();
+  }
+
   return result;
 };
 

nix-js/runtime-ts/src/thunk.ts

@@ -4,6 +4,8 @@
  */
 
 import type { NixValue, NixThunkInterface, NixStrictValue } from "./types";
+import { HAS_CONTEXT } from "./string-context";
+import { IS_PATH } from "./types";
 
 /**
  * Symbol used to mark objects as thunks
@@ -12,8 +14,9 @@ import type { NixValue, NixThunkInterface, NixStrictValue } from "./types";
 export const IS_THUNK = Symbol("is_thunk");
 
 const forceStack: NixThunk[] = [];
+const MAX_FORCE_DEPTH = 1000;
 
-export const DEBUG_THUNKS = { enabled: false };
+export const DEBUG_THUNKS = { enabled: true };
 
 /**
  * NixThunk class - represents a lazy, unevaluated expression
@@ -97,14 +100,29 @@ export const force = (value: NixValue): NixStrictValue => {
 
   if (DEBUG_THUNKS.enabled) {
     forceStack.push(thunk);
+    if (forceStack.length > MAX_FORCE_DEPTH) {
+      let msg = `force depth exceeded ${MAX_FORCE_DEPTH} at ${thunk}\n`;
+      msg += "Force chain (most recent first):\n";
+      for (let i = forceStack.length - 1; i >= Math.max(0, forceStack.length - 20); i--) {
+        const t = forceStack[i];
+        msg += `  ${i + 1}. ${t}`;
+        msg += "\n";
+      }
+      throw new Error(msg);
+    }
   }
   try {
     const result = force(func());
     thunk.result = result;
     return result;
+  } catch (e) {
+    thunk.func = func;
+    throw e;
   } finally {
+    if (DEBUG_THUNKS.enabled) {
       forceStack.pop();
     }
+  }
 };
 
 /**
@@ -116,3 +134,53 @@ export const force = (value: NixValue): NixStrictValue => {
 export const createThunk = (func: () => NixValue, label?: string): NixThunkInterface => {
   return new NixThunk(func, label);
 };
+
+/**
+ * Symbol to mark cyclic references detected during deep forcing
+ */
+export const IS_CYCLE = Symbol("is_cycle");
+
+/**
+ * Marker object for cyclic references
+ */
+export const CYCLE_MARKER = { [IS_CYCLE]: true };
+
+/**
+ * Deeply force a value, handling cycles by returning a special marker.
+ * Uses WeakSet to track seen objects and avoid infinite recursion.
+ * Returns a fully forced value where thunks are replaced with their results.
+ * Cyclic references are replaced with CYCLE_MARKER, preserving the container type.
+ */
+export const forceDeepSafe = (value: NixValue, seen: WeakSet<object> = new WeakSet()): NixStrictValue => {
+  const forced = force(value);
+
+  if (forced === null || typeof forced !== "object") {
+    return forced;
+  }
+
+  if (seen.has(forced)) {
+    if (Array.isArray(forced)) {
+      return [CYCLE_MARKER];
+    }
+    return CYCLE_MARKER;
+  }
+  seen.add(forced);
+
+  if (HAS_CONTEXT in forced || IS_PATH in forced) {
+    return forced;
+  }
+
+  if (Array.isArray(forced)) {
+    return forced.map((item) => forceDeepSafe(item, seen));
+  }
+
+  if (typeof forced === "object") {
+    const result: Record<string, NixValue> = {};
+    for (const [key, val] of Object.entries(forced)) {
+      result[key] = forceDeepSafe(val, seen);
+    }
+    return result;
+  }
+
+  return forced;
+};

nix-js/runtime-ts/src/type-assert.ts

@@ -16,7 +16,6 @@ import type {
 } from "./types";
 import { isStringWithContext, isNixPath } from "./types";
 import { force } from "./thunk";
-import { getStringValue } from "./string-context";
 import { isAttrs, isFunction, typeOf } from "./builtins/type-check";
 
 /**
@@ -32,15 +31,25 @@ export const forceList = (value: NixValue): NixList => {
 };
 
 /**
- * Force a value and assert it's a function
+ * Force a value and assert it's a function or functor
- * @throws TypeError if value is not a function after forcing
+ * @throws TypeError if value is not a function or functor after forcing
  */
 export const forceFunction = (value: NixValue): NixFunction => {
   const forced = force(value);
-  if (!isFunction(forced)) {
+  if (isFunction(forced)) {
-    throw new TypeError(`Expected function, got ${typeOf(forced)}`);
-  }
     return forced;
+  }
+  if (
+    typeof forced === "object" &&
+    !Array.isArray(forced) &&
+    forced !== null &&
+    "__functor" in forced
+  ) {
+    const functorSet = forced as NixAttrs;
+    const functor = forceFunction(functorSet.__functor);
+    return (arg: NixValue) => forceFunction(functor(functorSet))(arg);
+  }
+  throw new TypeError(`Expected function, got ${typeOf(forced)}`);
 };
 
 /**

nix-js/runtime-ts/src/types.ts

@@ -39,9 +39,11 @@ export class NixArgs {
   optional: string[];
   allowed: Set<string>;
   ellipsis: boolean;
-  constructor(required: string[], optional: string[], ellipsis: boolean) {
+  positions: Record<string, string>;
+  constructor(required: string[], optional: string[], positions: Record<string, string>, ellipsis: boolean) {
     this.required = required;
     this.optional = optional;
+    this.positions = positions;
     this.ellipsis = ellipsis;
     this.allowed = new Set(required.concat(optional));
   }
@@ -67,10 +69,11 @@ export const mkFunction = (
   f: (arg: NixValue) => NixValue,
   required: string[],
   optional: string[],
+  positions: Record<string, string>,
   ellipsis: boolean,
 ): NixFunction => {
   const func = f as NixFunction;
-  func.args = new NixArgs(required, optional, ellipsis);
+  func.args = new NixArgs(required, optional, positions, ellipsis);
   return func;
 };
 

nix-js/runtime-ts/src/types/global.d.ts

@@ -42,8 +42,10 @@ declare global {
         function op_read_dir(path: string): Record<string, string>;
         function op_path_exists(path: string): boolean;
         function op_sha256_hex(data: string): string;
+        function op_make_placeholder(output: string): string;
         function op_decode_span(span: string): { file: string | null; line: number | null; column: number | null };
         function op_make_store_path(ty: string, hash_hex: string, name: string): string;
+        function op_make_text_store_path(hash_hex: string, name: string, references: string[]): string;
         function op_output_path_name(drv_name: string, output_name: string): string;
         function op_make_fixed_output_path(
           hash_algo: string,
@@ -83,6 +85,14 @@ declare global {
         function op_to_file(name: string, contents: string, references: string[]): string;
         function op_copy_path_to_store(path: string): string;
         function op_get_env(key: string): string;
+        function op_walk_dir(path: string): [string, string][];
+        function op_add_filtered_path(
+          path: string,
+          name: string | null,
+          recursive: boolean,
+          sha256: string | null,
+          include_paths: string[],
+        ): string;
       }
     }
   }

nix-js/src/context.rs

@@ -1,28 +1,21 @@
 use std::path::Path;
 use std::ptr::NonNull;
 
-use hashbrown::{HashMap, HashSet};
+use hashbrown::HashMap;
 use itertools::Itertools as _;
-use petgraph::graphmap::DiGraphMap;
 use rnix::TextRange;
 use string_interner::DefaultStringInterner;
 
 use crate::codegen::{CodegenContext, compile};
 use crate::error::{Error, Result, Source};
 use crate::ir::{
-    Arg, ArgId, Bool, Builtin, Downgrade as _, DowngradeContext, ExprId, ExprRef, Ir, Null, SymId,
+    Arg, ArgId, Bool, Builtin, Downgrade as _, DowngradeContext, ExprId, Ir, Null, SymId, Thunk,
-    Thunk, ToIr as _, synthetic_span,
+    ToIr as _, synthetic_span,
 };
 use crate::runtime::{Runtime, RuntimeContext};
 use crate::store::{Store, StoreBackend, StoreConfig};
 use crate::value::Value;
 
-#[derive(Debug)]
-pub(crate) struct SccInfo {
-    /// list of SCCs (exprs, recursive)
-    pub(crate) sccs: Vec<(Vec<ExprId>, bool)>,
-}
-
 pub struct Context {
     ctx: Ctx,
     runtime: Runtime<Ctx>,
@@ -44,7 +37,7 @@ impl Context {
 
         tracing::debug!("Executing JavaScript");
         self.runtime
-            .eval(format!("Nix.force({code})"), &mut self.ctx)
+            .eval(format!("Nix.forceDeepSafe({code})"), &mut self.ctx)
     }
 
     pub fn compile_code(&mut self, source: Source) -> Result<String> {
@@ -256,14 +249,6 @@ impl RuntimeContext for Ctx {
     }
 }
 
-struct DependencyTracker {
-    graph: DiGraphMap<ExprId, ()>,
-    current_binding: Option<ExprId>,
-    let_scope_exprs: HashSet<ExprId>,
-    // The outer binding that owns this tracker (for nested let scopes in function params)
-    owner_binding: Option<ExprId>,
-}
-
 enum Scope<'ctx> {
     Global(&'ctx HashMap<SymId, ExprId>),
     Let(HashMap<SymId, ExprId>),
@@ -289,10 +274,10 @@ impl<'a, 'ctx> ScopeGuard<'a, 'ctx> {
 
 pub struct DowngradeCtx<'ctx> {
     ctx: &'ctx mut Ctx,
-    irs: Vec<Option<Ir>>,
+    irs: Vec<Ir>,
     scopes: Vec<Scope<'ctx>>,
     arg_id: usize,
-    dep_tracker_stack: Vec<DependencyTracker>,
+    thunk_scopes: Vec<Vec<(ExprId, ExprId)>>,
 }
 
 impl<'ctx> DowngradeCtx<'ctx> {
@@ -301,7 +286,7 @@ impl<'ctx> DowngradeCtx<'ctx> {
             scopes: vec![Scope::Global(global)],
             irs: vec![],
             arg_id: 0,
-            dep_tracker_stack: Vec::new(),
+            thunk_scopes: vec![Vec::new()],
             ctx,
         }
     }
@@ -309,18 +294,18 @@ impl<'ctx> DowngradeCtx<'ctx> {
 
 impl DowngradeContext for DowngradeCtx<'_> {
     fn new_expr(&mut self, expr: Ir) -> ExprId {
-        self.irs.push(Some(expr));
+        self.irs.push(expr);
         ExprId(self.ctx.irs.len() + self.irs.len() - 1)
     }
 
     fn new_arg(&mut self, span: TextRange) -> ExprId {
-        self.irs.push(Some(
+        self.irs.push(
             Arg {
                 inner: ArgId(self.arg_id),
                 span,
             }
             .to_ir(),
-        ));
+        );
         self.arg_id += 1;
         ExprId(self.ctx.irs.len() + self.irs.len() - 1)
     }
@@ -332,8 +317,6 @@ impl DowngradeContext for DowngradeCtx<'_> {
             self.irs
                 .get(id.0 - self.ctx.irs.len())
                 .expect("ExprId out of bounds")
-                .as_ref()
-                .expect("maybe_thunk called on an extracted expr")
         }
     }
 
@@ -346,14 +329,15 @@ impl DowngradeContext for DowngradeCtx<'_> {
             | Ir::Float(_)
             | Ir::Bool(_)
             | Ir::Null(_)
-            | Ir::Str(_) => id,
+            | Ir::Str(_)
-            _ => self.new_expr(
+            | Ir::Thunk(_) => id,
-                Thunk {
+            _ => {
-                    inner: id,
+                let span = ir.span();
-                    span: ir.span(),
+                let slot = self.reserve_slots(1).next().expect("reserve_slots failed");
+                self.replace_ir(slot, Thunk { inner: slot, span }.to_ir());
+                self.register_thunk(slot, id);
+                slot
             }
-                .to_ir(),
-            ),
         }
     }
 
@@ -375,45 +359,7 @@ impl DowngradeContext for DowngradeCtx<'_> {
                 }
                 Scope::Let(let_scope) => {
                     if let Some(&expr) = let_scope.get(&sym) {
-                        // Find which tracker contains this expression
+                        return Ok(self.new_expr(Thunk { inner: expr, span }.to_ir()));
-                        let expr_tracker_idx = self
-                            .dep_tracker_stack
-                            .iter()
-                            .position(|t| t.let_scope_exprs.contains(&expr));
-
-                        // Find the innermost tracker with a current_binding
-                        let current_tracker_idx = self
-                            .dep_tracker_stack
-                            .iter()
-                            .rposition(|t| t.current_binding.is_some());
-
-                        // Record dependency if both exist
-                        if let (Some(expr_idx), Some(curr_idx)) =
-                            (expr_tracker_idx, current_tracker_idx)
-                        {
-                            let current_binding = self.dep_tracker_stack[curr_idx]
-                                .current_binding
-                                .expect("current_binding not set");
-                            let owner_binding = self.dep_tracker_stack[curr_idx].owner_binding;
-
-                            // If referencing from inner scope to outer scope
-                            if curr_idx >= expr_idx {
-                                let tracker = &mut self.dep_tracker_stack[expr_idx];
-                                let from_node = current_binding;
-                                let to_node = expr;
-                                if curr_idx > expr_idx {
-                                    // Cross-scope reference: use owner_binding if available
-                                    if let Some(owner) = owner_binding {
-                                        tracker.graph.add_edge(owner, expr, ());
-                                    }
-                                } else {
-                                    // Same-level reference: record directly
-                                    tracker.graph.add_edge(from_node, to_node, ());
-                                }
-                            }
-                        }
-
-                        return Ok(self.new_expr(ExprRef { inner: expr, span }.to_ir()));
                     }
                 }
                 &Scope::Param(param_sym, expr) => {
@@ -456,22 +402,9 @@ impl DowngradeContext for DowngradeCtx<'_> {
         })
     }
 
-    fn extract_ir(&mut self, id: ExprId) -> Ir {
-        let local_id = id.0 - self.ctx.irs.len();
-        self.irs
-            .get_mut(local_id)
-            .expect("ExprId out of bounds")
-            .take()
-            .expect("extract_expr called on an already extracted expr")
-    }
-
     fn replace_ir(&mut self, id: ExprId, expr: Ir) {
         let local_id = id.0 - self.ctx.irs.len();
-        let _ = self
+        *self.irs.get_mut(local_id).expect("ExprId out of bounds") = expr;
-            .irs
-            .get_mut(local_id)
-            .expect("ExprId out of bounds")
-            .insert(expr);
     }
 
     fn get_current_source(&self) -> Source {
@@ -481,16 +414,25 @@ impl DowngradeContext for DowngradeCtx<'_> {
     #[allow(refining_impl_trait)]
     fn reserve_slots(&mut self, slots: usize) -> impl Iterator<Item = ExprId> + Clone + use<> {
         let start = self.ctx.irs.len() + self.irs.len();
-        self.irs.extend(std::iter::repeat_with(|| None).take(slots));
+        let range = (start..start + slots).map(ExprId);
-        (start..start + slots).map(ExprId)
+        let span = synthetic_span();
+        // Fill reserved slots with placeholder value
+        self.irs.extend(
+            range
+                .clone()
+                .map(|slot| Thunk { inner: slot, span }.to_ir()),
+        );
+        range
     }
 
     fn downgrade(mut self, root: rnix::ast::Expr) -> Result<ExprId> {
-        let root = root.downgrade(&mut self)?;
+        use crate::ir::TopLevel;
-        self.ctx
+        let body = root.downgrade(&mut self)?;
-            .irs
+        let thunks = self.pop_thunk_scope();
-            .extend(self.irs.into_iter().map(Option::unwrap));
+        let span = self.get_ir(body).span();
-        Ok(root)
+        let top_level = self.new_expr(TopLevel { body, thunks, span }.to_ir());
+        self.ctx.irs.extend(self.irs);
+        Ok(top_level)
     }
 
     fn with_let_scope<F, R>(&mut self, bindings: HashMap<SymId, ExprId>, f: F) -> R
@@ -515,83 +457,26 @@ impl DowngradeContext for DowngradeCtx<'_> {
     where
         F: FnOnce(&mut Self) -> R,
     {
+        let namespace = self.maybe_thunk(namespace);
         self.scopes.push(Scope::With(namespace));
         let mut guard = ScopeGuard { ctx: self };
         f(guard.as_ctx())
     }
 
-    fn push_dep_tracker(&mut self, slots: &[ExprId]) {
+    fn push_thunk_scope(&mut self) {
-        let mut graph = DiGraphMap::new();
+        self.thunk_scopes.push(Vec::new());
-        let mut let_scope_exprs = HashSet::new();
-
-        for &expr in slots.iter() {
-            graph.add_node(expr);
-            let_scope_exprs.insert(expr);
     }
 
-        self.dep_tracker_stack.push(DependencyTracker {
+    fn pop_thunk_scope(&mut self) -> Vec<(ExprId, ExprId)> {
-            graph,
+        self.thunk_scopes
-            current_binding: None,
-            let_scope_exprs,
-            owner_binding: None,
-        });
-    }
-
-    fn push_dep_tracker_with_owner(&mut self, slots: &[ExprId], owner: ExprId) {
-        let mut graph = DiGraphMap::new();
-        let mut let_scope_exprs = HashSet::new();
-
-        for &expr in slots.iter() {
-            graph.add_node(expr);
-            let_scope_exprs.insert(expr);
-        }
-
-        self.dep_tracker_stack.push(DependencyTracker {
-            graph,
-            current_binding: None,
-            let_scope_exprs,
-            owner_binding: Some(owner),
-        });
-    }
-
-    fn get_current_binding(&self) -> Option<ExprId> {
-        self.dep_tracker_stack
-            .last()
-            .and_then(|t| t.current_binding)
-    }
-
-    fn set_current_binding(&mut self, expr: Option<ExprId>) {
-        if let Some(tracker) = self.dep_tracker_stack.last_mut() {
-            tracker.current_binding = expr;
-        }
-    }
-
-    fn pop_dep_tracker(&mut self) -> Result<SccInfo> {
-        let tracker = self
-            .dep_tracker_stack
             .pop()
-            .expect("pop_dep_tracker without active tracker");
+            .expect("pop_thunk_scope without active scope")
-
-        use petgraph::algo::kosaraju_scc;
-        let sccs = kosaraju_scc(&tracker.graph);
-
-        let mut sccs_topo = Vec::new();
-
-        for scc_nodes in sccs.iter() {
-            let mut scc_exprs = Vec::new();
-            let mut is_recursive = scc_nodes.len() > 1;
-
-            for &expr in scc_nodes {
-                scc_exprs.push(expr);
-
-                if !is_recursive && tracker.graph.contains_edge(expr, expr) {
-                    is_recursive = true;
-                }
     }
 
-            sccs_topo.push((scc_exprs, is_recursive));
+    fn register_thunk(&mut self, slot: ExprId, inner: ExprId) {
-        }
+        self.thunk_scopes
-
+            .last_mut()
-        Ok(SccInfo { sccs: sccs_topo })
+            .expect("register_thunk without active scope")
+            .push((slot, inner));
     }
 }

nix-js/src/error.rs

@@ -44,6 +44,13 @@ impl From<Source> for NamedSource<Arc<str>> {
 }
 
 impl Source {
+    pub fn new_file(path: PathBuf) -> std::io::Result<Self> {
+        Ok(Source {
+            src: std::fs::read_to_string(&path)?.into(),
+            ty: crate::error::SourceType::File(Arc::new(path)),
+        })
+    }
+
     pub fn new_eval(src: String) -> Result<Self> {
         Ok(Self {
             ty: std::env::current_dir()
@@ -214,8 +221,8 @@ pub struct StackFrame {
     pub src: NamedSource<Arc<str>>,
 }
 
-const MAX_STACK_FRAMES: usize = 10;
+const MAX_STACK_FRAMES: usize = 20;
-const FRAMES_AT_START: usize = 5;
+const FRAMES_AT_START: usize = 15;
 const FRAMES_AT_END: usize = 5;
 
 pub(crate) fn parse_js_error(error: Box<JsError>, ctx: &impl RuntimeContext) -> Error {
@@ -234,7 +241,11 @@ pub(crate) fn parse_js_error(error: Box<JsError>, ctx: &impl RuntimeContext) ->
     } else {
         (None, None, Vec::new())
     };
-    let stack_trace = truncate_stack_trace(frames);
+    let stack_trace = if std::env::var("NIX_JS_STACK_TRACE").is_ok() {
+        truncate_stack_trace(frames)
+    } else {
+        Vec::new()
+    };
     let message = error.get_message().to_string();
     let js_backtrace = error.stack.map(|stack| {
         stack
@@ -272,7 +283,7 @@ fn parse_frames(stack: &str, ctx: &impl RuntimeContext) -> Vec<NixStackFrame> {
     let mut frames = Vec::new();
 
     for line in stack.lines() {
-        // Format: NIX_STACK_FRAME:start:end[:extra_data]
+        // Format: NIX_STACK_FRAME:source_id:start:end[:extra_data]
         let Some(rest) = line.strip_prefix("NIX_STACK_FRAME:") else {
             continue;
         };

nix-js/src/ir.rs

@@ -3,9 +3,7 @@ use hashbrown::HashMap;
 use rnix::{TextRange, ast};
 use string_interner::symbol::SymbolU32;
 
-use crate::context::SccInfo;
+use crate::error::{Result, Source};
-use crate::error::{Error, Result, Source};
-use crate::value::format_symbol;
 use nix_js_macros::ir;
 
 mod downgrade;
@@ -29,7 +27,6 @@ pub trait DowngradeContext {
     fn lookup(&mut self, sym: SymId, span: TextRange) -> Result<ExprId>;
 
     fn get_ir(&self, id: ExprId) -> &Ir;
-    fn extract_ir(&mut self, id: ExprId) -> Ir;
     fn replace_ir(&mut self, id: ExprId, expr: Ir);
     fn reserve_slots(&mut self, slots: usize) -> impl Iterator<Item = ExprId> + Clone + use<Self>;
     fn get_current_source(&self) -> Source;
@@ -44,11 +41,9 @@ pub trait DowngradeContext {
     where
         F: FnOnce(&mut Self) -> R;
 
-    fn push_dep_tracker(&mut self, slots: &[ExprId]);
+    fn push_thunk_scope(&mut self);
-    fn push_dep_tracker_with_owner(&mut self, slots: &[ExprId], owner: ExprId);
+    fn pop_thunk_scope(&mut self) -> Vec<(ExprId, ExprId)>;
-    fn get_current_binding(&self) -> Option<ExprId>;
+    fn register_thunk(&mut self, slot: ExprId, inner: ExprId);
-    fn set_current_binding(&mut self, expr: Option<ExprId>);
-    fn pop_dep_tracker(&mut self) -> Result<SccInfo>;
 }
 
 ir! {
@@ -69,147 +64,17 @@ ir! {
     If { pub cond: ExprId, pub consq: ExprId, pub alter: ExprId },
     Call { pub func: ExprId, pub arg: ExprId },
     Assert { pub assertion: ExprId, pub expr: ExprId, pub assertion_raw: String },
-    ConcatStrings { pub parts: Vec<ExprId> },
+    ConcatStrings { pub parts: Vec<ExprId>, pub force_string: bool },
     Path { pub expr: ExprId },
-    Func { pub body: ExprId, pub param: Option<Param>, pub arg: ExprId },
+    Func { pub body: ExprId, pub param: Option<Param>, pub arg: ExprId, pub thunks: Vec<(ExprId, ExprId)> },
-    Let { pub binding_sccs: SccInfo, pub body: ExprId },
+    TopLevel { pub body: ExprId, pub thunks: Vec<(ExprId, ExprId)> },
     Arg(ArgId),
-    ExprRef(ExprId),
     Thunk(ExprId),
     Builtins,
     Builtin(SymId),
     CurPos,
 }
 
-impl Ir {
-    pub fn span(&self) -> TextRange {
-        match self {
-            Ir::Int(i) => i.span,
-            Ir::Float(f) => f.span,
-            Ir::Bool(b) => b.span,
-            Ir::Null(n) => n.span,
-            Ir::Str(s) => s.span,
-            Ir::AttrSet(a) => a.span,
-            Ir::List(l) => l.span,
-            Ir::HasAttr(h) => h.span,
-            Ir::BinOp(b) => b.span,
-            Ir::UnOp(u) => u.span,
-            Ir::Select(s) => s.span,
-            Ir::If(i) => i.span,
-            Ir::Call(c) => c.span,
-            Ir::Assert(a) => a.span,
-            Ir::ConcatStrings(c) => c.span,
-            Ir::Path(p) => p.span,
-            Ir::Func(f) => f.span,
-            Ir::Let(l) => l.span,
-            Ir::Arg(a) => a.span,
-            Ir::ExprRef(e) => e.span,
-            Ir::Thunk(t) => t.span,
-            Ir::Builtins(b) => b.span,
-            Ir::Builtin(b) => b.span,
-            Ir::CurPos(c) => c.span,
-        }
-    }
-}
-
-impl AttrSet {
-    fn _insert(
-        &mut self,
-        mut path: impl Iterator<Item = Attr>,
-        name: Attr,
-        value: ExprId,
-        ctx: &mut impl DowngradeContext,
-    ) -> Result<()> {
-        if let Some(attr) = path.next() {
-            // If the path is not yet exhausted, we need to recurse deeper.
-            match attr {
-                Attr::Str(ident, span) => {
-                    // If the next attribute is a static string.
-                    if let Some(&(id, _)) = self.stcs.get(&ident) {
-                        // If a sub-attrset already exists, recurse into it.
-                        let mut ir = ctx.extract_ir(id);
-                        let result = ir
-                            .as_mut()
-                            .try_unwrap_attr_set()
-                            .map_err(|_| {
-                                // This path segment exists but is not an attrset, which is an error.
-                                Error::downgrade_error(format!(
-                                    "attribute '{}' already defined but is not an attribute set",
-                                    format_symbol(ctx.get_sym(ident)),
-                                ),
-                                    ctx.get_current_source(),
-                                    span
-                                )
-                            })
-                            .and_then(|attrs| attrs._insert(path, name, value, ctx));
-                        ctx.replace_ir(id, ir);
-                        result?;
-                    } else {
-                        // Create a new sub-attrset because this path doesn't exist yet.
-                        // FIXME: span
-                        let mut attrs = AttrSet {
-                            stcs: Default::default(),
-                            dyns: Default::default(),
-                            span,
-                        };
-                        attrs._insert(path, name, value, ctx)?;
-                        let attrs_expr = ctx.new_expr(attrs.to_ir());
-                        self.stcs.insert(ident, (attrs_expr, span));
-                    }
-                    Ok(())
-                }
-                Attr::Dynamic(dynamic, span) => {
-                    // If the next attribute is a dynamic expression, we must create a new sub-attrset.
-                    // We cannot merge with existing dynamic attributes at this stage.
-                    // FIXME: span
-                    let mut attrs = AttrSet {
-                        stcs: Default::default(),
-                        dyns: Default::default(),
-                        span,
-                    };
-                    attrs._insert(path, name, value, ctx)?;
-                    self.dyns.push((dynamic, ctx.new_expr(attrs.to_ir()), span));
-                    Ok(())
-                }
-            }
-        } else {
-            // This is the final attribute in the path, so insert the value here.
-            match name {
-                Attr::Str(ident, span) => {
-                    if self.stcs.insert(ident, (value, span)).is_some() {
-                        return Err(Error::downgrade_error(
-                            format!(
-                                "attribute '{}' already defined",
-                                format_symbol(ctx.get_sym(ident)),
-                            ),
-                            ctx.get_current_source(),
-                            span,
-                        ));
-                    }
-                }
-                Attr::Dynamic(dynamic, span) => {
-                    self.dyns.push((dynamic, value, span));
-                }
-            }
-            Ok(())
-        }
-    }
-
-    fn insert(
-        &mut self,
-        path: Vec<Attr>,
-        value: ExprId,
-        ctx: &mut impl DowngradeContext,
-    ) -> Result<()> {
-        let mut path = path.into_iter();
-        // The last part of the path is the name of the attribute to be inserted.
-        let name = path
-            .next_back()
-            .expect("empty attrpath passed. this is a bug");
-        self._insert(path, name, value, ctx)
-    }
-}
-
 #[repr(transparent)]
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
 pub struct ExprId(pub usize);
@@ -221,6 +86,7 @@ pub type SymId = SymbolU32;
 pub struct ArgId(pub usize);
 
 /// Represents a key in an attribute path.
+#[allow(unused)]
 #[derive(Debug, TryUnwrap)]
 pub enum Attr {
     /// A dynamic attribute key, which is an expression that must evaluate to a string.
@@ -307,7 +173,7 @@ impl From<ast::UnaryOpKind> for UnOpKind {
 /// Describes the parameters of a function.
 #[derive(Debug)]
 pub struct Param {
-    pub required: Vec<SymId>,
+    pub required: Vec<(SymId, TextRange)>,
-    pub optional: Vec<SymId>,
+    pub optional: Vec<(SymId, TextRange)>,
     pub ellipsis: bool,
 }

nix-js/src/ir/downgrade.rs

@@ -139,7 +139,14 @@ impl<Ctx: DowngradeContext> Downgrade<Ctx> for ast::Path {
                 part
             }
         } else {
-            ctx.new_expr(ConcatStrings { parts, span }.to_ir())
+            ctx.new_expr(
+                ConcatStrings {
+                    parts,
+                    span,
+                    force_string: false,
+                }
+                .to_ir(),
+            )
         };
         Ok(ctx.new_expr(Path { expr, span }.to_ir()))
     }
@@ -158,7 +165,7 @@ impl<Ctx: DowngradeContext> Downgrade<Ctx> for ast::Str {
                 ast::InterpolPart::Literal(lit) => Ok(ctx.new_expr(Str { val: lit, span }.to_ir())),
                 ast::InterpolPart::Interpolation(interpol) => {
                     let inner = interpol.expr().unwrap().downgrade(ctx)?;
-                    Ok(ctx.new_expr(Thunk { inner, span }.to_ir()))
+                    Ok(ctx.maybe_thunk(inner))
                 }
             })
             .collect::<Result<Vec<_>>>()?;
@@ -166,7 +173,14 @@ impl<Ctx: DowngradeContext> Downgrade<Ctx> for ast::Str {
         Ok(if is_single_literal {
             parts.into_iter().next().unwrap()
         } else {
-            ctx.new_expr(ConcatStrings { parts, span }.to_ir())
+            ctx.new_expr(
+                ConcatStrings {
+                    parts,
+                    span,
+                    force_string: true,
+                }
+                .to_ir(),
+            )
         })
     }
 }
@@ -220,31 +234,7 @@ impl<Ctx: DowngradeContext> Downgrade<Ctx> for ast::AttrSet {
 
         // rec { a = 1; b = a; } => let a = 1; b = a; in { inherit a b; }
         let entries: Vec<_> = self.entries().collect();
-        let (binding_sccs, body) = downgrade_let_bindings(entries, ctx, |ctx, binding_keys| {
+        downgrade_rec_bindings(entries, ctx, span)
-            // Create plain attrset as body with inherit
-            let mut attrs = AttrSet {
-                stcs: HashMap::new(),
-                dyns: Vec::new(),
-                span,
-            };
-
-            for sym in binding_keys {
-                // FIXME: span
-                let expr = ctx.lookup(*sym, synthetic_span())?;
-                attrs.stcs.insert(*sym, (expr, synthetic_span()));
-            }
-
-            Ok(ctx.new_expr(attrs.to_ir()))
-        })?;
-
-        Ok(ctx.new_expr(
-            Let {
-                body,
-                binding_sccs,
-                span,
-            }
-            .to_ir(),
-        ))
     }
 }
 
@@ -308,17 +298,8 @@ impl<Ctx: DowngradeContext> Downgrade<Ctx> for ast::Select {
         let expr = self.expr().unwrap().downgrade(ctx)?;
         let attrpath = downgrade_attrpath(self.attrpath().unwrap(), ctx)?;
         let default = if let Some(default) = self.default_expr() {
-            let span = default.syntax().text_range();
             let default_expr = default.downgrade(ctx)?;
-            Some(
+            Some(ctx.maybe_thunk(default_expr))
-                ctx.new_expr(
-                    Thunk {
-                        inner: default_expr,
-                        span,
-                    }
-                    .to_ir(),
-                ),
-            )
         } else {
             None
         };
@@ -340,10 +321,9 @@ impl<Ctx: DowngradeContext> Downgrade<Ctx> for ast::Select {
 impl<Ctx: DowngradeContext> Downgrade<Ctx> for ast::LegacyLet {
     fn downgrade(self, ctx: &mut Ctx) -> Result<ExprId> {
         let span = self.syntax().text_range();
-        let bindings = downgrade_static_attrs(self, ctx)?;
+        let entries: Vec<_> = self.entries().collect();
-        let binding_keys: Vec<_> = bindings.keys().copied().collect();
+        let attrset_expr = downgrade_let_bindings(entries, ctx, span, |ctx, binding_keys| {
-
+            // Create plain attrset as body with inherit
-        let attrset_expr = ctx.with_let_scope(bindings, |ctx| {
             let mut attrs = AttrSet {
                 stcs: HashMap::new(),
                 dyns: Vec::new(),
@@ -351,12 +331,11 @@ impl<Ctx: DowngradeContext> Downgrade<Ctx> for ast::LegacyLet {
             };
 
             for sym in binding_keys {
-                // FIXME: span
+                let expr = ctx.lookup(*sym, synthetic_span())?;
-                let expr = ctx.lookup(sym, synthetic_span())?;
+                attrs.stcs.insert(*sym, (expr, synthetic_span()));
-                attrs.stcs.insert(sym, (expr, synthetic_span()));
             }
 
-            Result::Ok(ctx.new_expr(attrs.to_ir()))
+            Ok(ctx.new_expr(attrs.to_ir()))
         })?;
 
         let body_sym = ctx.new_sym("body".to_string());
@@ -378,17 +357,9 @@ impl<Ctx: DowngradeContext> Downgrade<Ctx> for ast::LetIn {
         let body_expr = self.body().unwrap();
         let span = self.syntax().text_range();
 
-        let (binding_sccs, body) =
+        downgrade_let_bindings(entries, ctx, span, |ctx, _binding_keys| {
-            downgrade_let_bindings(entries, ctx, |ctx, _binding_keys| body_expr.downgrade(ctx))?;
+            body_expr.downgrade(ctx)
-
+        })
-        Ok(ctx.new_expr(
-            Let {
-                body,
-                binding_sccs,
-                span,
-            }
-            .to_ir(),
-        ))
     }
 }
 
@@ -412,9 +383,10 @@ impl<Ctx: DowngradeContext> Downgrade<Ctx> for ast::Lambda {
         let raw_param = self.param().unwrap();
         let arg = ctx.new_arg(raw_param.syntax().text_range());
 
+        ctx.push_thunk_scope();
+
         let param;
         let body;
-        let span = self.body().unwrap().syntax().text_range();
 
         match raw_param {
             ast::Param::IdentParam(id) => {
@@ -436,7 +408,6 @@ impl<Ctx: DowngradeContext> Downgrade<Ctx> for ast::Lambda {
 
                 let PatternBindings {
                     body: inner_body,
-                    scc_info,
                     required,
                     optional,
                 } = downgrade_pattern_bindings(pat_entries, alias, arg, ctx, |ctx, _| {
@@ -449,24 +420,18 @@ impl<Ctx: DowngradeContext> Downgrade<Ctx> for ast::Lambda {
                     ellipsis,
                 });
 
-                body = ctx.new_expr(
+                body = inner_body;
-                    Let {
-                        body: inner_body,
-                        binding_sccs: scc_info,
-                        span,
-                    }
-                    .to_ir(),
-                );
             }
         }
 
+        let thunks = ctx.pop_thunk_scope();
         let span = self.syntax().text_range();
-        // The function's body and parameters are now stored directly in the `Func` node.
         Ok(ctx.new_expr(
             Func {
                 body,
                 param,
                 arg,
+                thunks,
                 span,
             }
             .to_ir(),

nix-js/src/nix_hash.rs

@@ -41,6 +41,45 @@ pub fn nix_base32_encode(bytes: &[u8]) -> String {
     result
 }
 
+pub fn nix_base32_decode(input: &str) -> Option<Vec<u8>> {
+    let len = input.len() * 5 / 8;
+    let mut bytes = vec![0u8; len];
+
+    for (n, ch) in input.chars().rev().enumerate() {
+        let digit = NIX_BASE32_CHARS.iter().position(|&c| c == ch as u8)? as u16;
+        let b = n * 5;
+        let i = b / 8;
+        let j = b % 8;
+        if i < len {
+            bytes[i] |= (digit << j) as u8;
+        }
+        if j > 3 && i + 1 < len {
+            bytes[i + 1] |= (digit >> (8 - j)) as u8;
+        }
+    }
+
+    Some(bytes)
+}
+
+pub fn decode_hash_to_hex(hash_str: &str) -> Option<String> {
+    if let Some(rest) = hash_str.strip_prefix("sha256:") {
+        return decode_hash_to_hex(rest);
+    }
+    if let Some(base64_str) = hash_str.strip_prefix("sha256-") {
+        use base64::{Engine, engine::general_purpose::STANDARD};
+        let bytes = STANDARD.decode(base64_str).ok()?;
+        return Some(hex::encode(bytes));
+    }
+    if hash_str.len() == 64 && hash_str.chars().all(|c| c.is_ascii_hexdigit()) {
+        return Some(hash_str.to_string());
+    }
+    if hash_str.len() == 52 {
+        let bytes = nix_base32_decode(hash_str)?;
+        return Some(hex::encode(bytes));
+    }
+    None
+}
+
 pub fn make_store_path(store_dir: &str, ty: &str, hash_hex: &str, name: &str) -> String {
     let s = format!("{}:sha256:{}:{}:{}", ty, hash_hex, store_dir, name);
 
@@ -54,6 +93,20 @@ pub fn make_store_path(store_dir: &str, ty: &str, hash_hex: &str, name: &str) ->
     format!("{}/{}-{}", store_dir, encoded, name)
 }
 
+pub fn make_text_store_path(
+    store_dir: &str,
+    hash_hex: &str,
+    name: &str,
+    references: &[String],
+) -> String {
+    let mut ty = String::from("text");
+    for reference in references {
+        ty.push(':');
+        ty.push_str(reference);
+    }
+    make_store_path(store_dir, &ty, hash_hex, name)
+}
+
 pub fn output_path_name(drv_name: &str, output_name: &str) -> String {
     if output_name == "out" {
         drv_name.to_string()

nix-js/src/runtime.rs

@@ -49,8 +49,10 @@ fn runtime_extension<Ctx: RuntimeContext>() -> Extension {
         op_path_exists(),
         op_resolve_path(),
         op_sha256_hex(),
+        op_make_placeholder(),
         op_decode_span::<Ctx>(),
         op_make_store_path::<Ctx>(),
+        op_make_text_store_path::<Ctx>(),
         op_output_path_name(),
         op_make_fixed_output_path::<Ctx>(),
         op_add_path::<Ctx>(),
@@ -58,6 +60,8 @@ fn runtime_extension<Ctx: RuntimeContext>() -> Extension {
         op_to_file::<Ctx>(),
         op_copy_path_to_store::<Ctx>(),
         op_get_env(),
+        op_walk_dir(),
+        op_add_filtered_path::<Ctx>(),
     ];
     ops.extend(crate::fetcher::register_ops::<Ctx>());
 
@@ -130,22 +134,19 @@ fn op_import<Ctx: RuntimeContext>(
     }
 
     let current_dir = ctx.get_current_dir();
-    let mut absolute_path = current_dir
+    let mut absolute_path = current_dir.join(&path);
-        .join(&path)
+    // Do NOT resolve symlinks (eval-okay-symlink-resolution)
-        .canonicalize()
+    // TODO: is this correct?
-        .map_err(|e| format!("Failed to resolve path {}: {}", path, e))?;
+    // .canonicalize()
+    // .map_err(|e| format!("Failed to resolve path {}: {}", path, e))?;
     if absolute_path.is_dir() {
         absolute_path.push("default.nix")
     }
 
     tracing::info!("Importing file: {}", absolute_path.display());
 
-    let content = std::fs::read_to_string(absolute_path.as_path())
+    let source = Source::new_file(absolute_path.clone())
         .map_err(|e| format!("Failed to read {}: {}", absolute_path.display(), e))?;
-    let source = Source {
-        ty: crate::error::SourceType::File(absolute_path.into()),
-        src: content.into(),
-    };
 
     tracing::debug!("Compiling file");
     ctx.add_source(source.clone());
@@ -161,7 +162,17 @@ fn op_read_file(#[string] path: String) -> std::result::Result<String, NixError>
 
 #[deno_core::op2(fast)]
 fn op_path_exists(#[string] path: String) -> bool {
-    std::path::Path::new(&path).exists()
+    let must_be_dir = path.ends_with('/') || path.ends_with("/.");
+    let p = Path::new(&path);
+
+    if must_be_dir {
+        match std::fs::metadata(p) {
+            Ok(m) => m.is_dir(),
+            Err(_) => false,
+        }
+    } else {
+        std::fs::symlink_metadata(p).is_ok()
+    }
 }
 
 #[deno_core::op2]
@@ -274,6 +285,18 @@ fn op_sha256_hex(#[string] data: String) -> String {
     crate::nix_hash::sha256_hex(&data)
 }
 
+#[deno_core::op2]
+#[string]
+fn op_make_placeholder(#[string] output: String) -> String {
+    use sha2::{Digest, Sha256};
+    let input = format!("nix-output:{}", output);
+    let mut hasher = Sha256::new();
+    hasher.update(input.as_bytes());
+    let hash: [u8; 32] = hasher.finalize().into();
+    let encoded = crate::nix_hash::nix_base32_encode(&hash);
+    format!("/{}", encoded)
+}
+
 #[deno_core::op2]
 #[serde]
 fn op_decode_span<Ctx: RuntimeContext>(
@@ -338,6 +361,20 @@ fn op_make_store_path<Ctx: RuntimeContext>(
     crate::nix_hash::make_store_path(store_dir, &ty, &hash_hex, &name)
 }
 
+#[deno_core::op2]
+#[string]
+fn op_make_text_store_path<Ctx: RuntimeContext>(
+    state: &mut OpState,
+    #[string] hash_hex: String,
+    #[string] name: String,
+    #[serde] references: Vec<String>,
+) -> String {
+    let ctx: &Ctx = state.get_ctx();
+    let store = ctx.get_store();
+    let store_dir = store.get_store_dir();
+    crate::nix_hash::make_text_store_path(store_dir, &hash_hex, &name, &references)
+}
+
 #[deno_core::op2]
 #[string]
 fn op_output_path_name(#[string] drv_name: String, #[string] output_name: String) -> String {
@@ -400,7 +437,8 @@ fn op_add_path<Ctx: RuntimeContext>(
     });
 
     let computed_hash = if recursive {
-        compute_nar_hash(path_obj)?
+        crate::nar::compute_nar_hash(path_obj)
+            .map_err(|e| NixError::from(format!("failed to compute NAR hash: {}", e)))?
     } else {
         if !path_obj.is_file() {
             return Err(NixError::from(
@@ -415,60 +453,35 @@ fn op_add_path<Ctx: RuntimeContext>(
         hex::encode(hasher.finalize())
     };
 
-    if let Some(expected_hash) = sha256
+    if let Some(expected_hash) = sha256 {
-        && computed_hash != expected_hash
+        let expected_hex = crate::nix_hash::decode_hash_to_hex(&expected_hash)
-    {
+            .ok_or_else(|| NixError::from(format!("invalid hash format: {}", expected_hash)))?;
+        if computed_hash != expected_hex {
             return Err(NixError::from(format!(
                 "hash mismatch for path '{}': expected {}, got {}",
-            path, expected_hash, computed_hash
+                path, expected_hex, computed_hash
             )));
         }
+    }
 
     let ctx: &Ctx = state.get_ctx();
     let store = ctx.get_store();
 
-    let store_path = store
+    let store_path = if recursive {
+        store
             .add_to_store_from_path(&computed_name, path_obj, vec![])
-        .map_err(|e| NixError::from(format!("failed to add path to store: {}", e)))?;
+            .map_err(|e| NixError::from(format!("failed to add path to store: {}", e)))?
+    } else {
+        let contents = fs::read(path_obj)
+            .map_err(|e| NixError::from(format!("failed to read '{}': {}", path, e)))?;
+        store
+            .add_to_store(&computed_name, &contents, false, vec![])
+            .map_err(|e| NixError::from(format!("failed to add to store: {}", e)))?
+    };
 
     Ok(store_path)
 }
 
-fn compute_nar_hash(path: &std::path::Path) -> std::result::Result<String, NixError> {
-    use sha2::{Digest, Sha256};
-    use std::fs;
-
-    if path.is_file() {
-        let contents =
-            fs::read(path).map_err(|e| NixError::from(format!("failed to read file: {}", e)))?;
-        let mut hasher = Sha256::new();
-        hasher.update(&contents);
-        Ok(hex::encode(hasher.finalize()))
-    } else if path.is_dir() {
-        let mut entries: Vec<_> = fs::read_dir(path)
-            .map_err(|e| NixError::from(format!("failed to read directory: {}", e)))?
-            .filter_map(std::result::Result::ok)
-            .collect();
-
-        entries.sort_by_key(|e| e.file_name());
-
-        let mut hasher = Sha256::new();
-        for entry in entries {
-            let entry_path = entry.path();
-            let entry_name = entry.file_name();
-
-            hasher.update(entry_name.to_string_lossy().as_bytes());
-
-            let entry_hash = compute_nar_hash(&entry_path)?;
-            hasher.update(entry_hash.as_bytes());
-        }
-
-        Ok(hex::encode(hasher.finalize()))
-    } else {
-        Ok(String::new())
-    }
-}
-
 #[deno_core::op2]
 #[string]
 fn op_store_path<Ctx: RuntimeContext>(
@@ -539,7 +552,167 @@ fn op_copy_path_to_store<Ctx: RuntimeContext>(
 #[deno_core::op2]
 #[string]
 fn op_get_env(#[string] key: String) -> std::result::Result<String, NixError> {
-    Ok(std::env::var(key).map_err(|err| format!("Failed to read env var: {err}"))?)
+    match std::env::var(key) {
+        Ok(val) => Ok(val),
+        Err(std::env::VarError::NotPresent) => Ok("".into()),
+        Err(err) => Err(format!("Failed to read env var: {err}").into()),
+    }
+}
+
+#[deno_core::op2]
+#[serde]
+fn op_walk_dir(#[string] path: String) -> std::result::Result<Vec<(String, String)>, NixError> {
+    fn walk_recursive(
+        base: &Path,
+        current: &Path,
+        results: &mut Vec<(String, String)>,
+    ) -> std::result::Result<(), NixError> {
+        let entries = std::fs::read_dir(current)
+            .map_err(|e| NixError::from(format!("failed to read directory: {}", e)))?;
+
+        for entry in entries {
+            let entry =
+                entry.map_err(|e| NixError::from(format!("failed to read entry: {}", e)))?;
+            let path = entry.path();
+            let rel_path = path
+                .strip_prefix(base)
+                .map_err(|e| NixError::from(format!("failed to get relative path: {}", e)))?
+                .to_string_lossy()
+                .to_string();
+
+            let file_type = entry
+                .file_type()
+                .map_err(|e| NixError::from(format!("failed to get file type: {}", e)))?;
+
+            let type_str = if file_type.is_dir() {
+                "directory"
+            } else if file_type.is_symlink() {
+                "symlink"
+            } else {
+                "regular"
+            };
+
+            results.push((rel_path.clone(), type_str.to_string()));
+
+            if file_type.is_dir() {
+                walk_recursive(base, &path, results)?;
+            }
+        }
+        Ok(())
+    }
+
+    let path = Path::new(&path);
+    if !path.is_dir() {
+        return Err(NixError::from(format!(
+            "{} is not a directory",
+            path.display()
+        )));
+    }
+
+    let mut results = Vec::new();
+    walk_recursive(path, path, &mut results)?;
+    Ok(results)
+}
+
+#[deno_core::op2]
+#[string]
+fn op_add_filtered_path<Ctx: RuntimeContext>(
+    state: &mut OpState,
+    #[string] src_path: String,
+    #[string] name: Option<String>,
+    recursive: bool,
+    #[string] sha256: Option<String>,
+    #[serde] include_paths: Vec<String>,
+) -> std::result::Result<String, NixError> {
+    use sha2::{Digest, Sha256};
+    use std::fs;
+
+    let src = Path::new(&src_path);
+    if !src.exists() {
+        return Err(NixError::from(format!(
+            "path '{}' does not exist",
+            src_path
+        )));
+    }
+
+    let computed_name = name.unwrap_or_else(|| {
+        src.file_name()
+            .and_then(|n| n.to_str())
+            .unwrap_or("source")
+            .to_string()
+    });
+
+    let temp_dir = tempfile::tempdir()
+        .map_err(|e| NixError::from(format!("failed to create temp dir: {}", e)))?;
+    let dest = temp_dir.path().join(&computed_name);
+
+    fs::create_dir_all(&dest)
+        .map_err(|e| NixError::from(format!("failed to create dest dir: {}", e)))?;
+
+    for rel_path in &include_paths {
+        let src_file = src.join(rel_path);
+        let dest_file = dest.join(rel_path);
+
+        if let Some(parent) = dest_file.parent() {
+            fs::create_dir_all(parent)
+                .map_err(|e| NixError::from(format!("failed to create dir: {}", e)))?;
+        }
+
+        let metadata = fs::symlink_metadata(&src_file)
+            .map_err(|e| NixError::from(format!("failed to read metadata: {}", e)))?;
+
+        if metadata.is_symlink() {
+            let target = fs::read_link(&src_file)
+                .map_err(|e| NixError::from(format!("failed to read symlink: {}", e)))?;
+            #[cfg(unix)]
+            std::os::unix::fs::symlink(&target, &dest_file)
+                .map_err(|e| NixError::from(format!("failed to create symlink: {}", e)))?;
+            #[cfg(not(unix))]
+            return Err(NixError::from("symlinks not supported on this platform"));
+        } else if metadata.is_dir() {
+            fs::create_dir_all(&dest_file)
+                .map_err(|e| NixError::from(format!("failed to create dir: {}", e)))?;
+        } else {
+            fs::copy(&src_file, &dest_file)
+                .map_err(|e| NixError::from(format!("failed to copy file: {}", e)))?;
+        }
+    }
+
+    let computed_hash = if recursive {
+        crate::nar::compute_nar_hash(&dest)
+            .map_err(|e| NixError::from(format!("failed to compute NAR hash: {}", e)))?
+    } else {
+        if !dest.is_file() {
+            return Err(NixError::from(
+                "when 'recursive' is false, path must be a regular file",
+            ));
+        }
+        let contents =
+            fs::read(&dest).map_err(|e| NixError::from(format!("failed to read file: {}", e)))?;
+        let mut hasher = Sha256::new();
+        hasher.update(&contents);
+        hex::encode(hasher.finalize())
+    };
+
+    if let Some(expected_hash) = sha256 {
+        let expected_hex = crate::nix_hash::decode_hash_to_hex(&expected_hash)
+            .ok_or_else(|| NixError::from(format!("invalid hash format: {}", expected_hash)))?;
+        if computed_hash != expected_hex {
+            return Err(NixError::from(format!(
+                "hash mismatch for path '{}': expected {}, got {}",
+                src_path, expected_hex, computed_hash
+            )));
+        }
+    }
+
+    let ctx: &Ctx = state.get_ctx();
+    let store = ctx.get_store();
+
+    let store_path = store
+        .add_to_store_from_path(&computed_name, &dest, vec![])
+        .map_err(|e| NixError::from(format!("failed to add path to store: {}", e)))?;
+
+    Ok(store_path)
 }
 
 pub(crate) struct Runtime<Ctx: RuntimeContext> {
@@ -548,6 +721,7 @@ pub(crate) struct Runtime<Ctx: RuntimeContext> {
     primop_metadata_symbol: v8::Global<v8::Symbol>,
     has_context_symbol: v8::Global<v8::Symbol>,
     is_path_symbol: v8::Global<v8::Symbol>,
+    is_cycle_symbol: v8::Global<v8::Symbol>,
     _marker: PhantomData<Ctx>,
 }
 
@@ -556,6 +730,8 @@ impl<Ctx: RuntimeContext> Runtime<Ctx> {
         // Initialize V8 once
         static INIT: Once = Once::new();
         INIT.call_once(|| {
+            // First flag is always not recognized
+            assert_eq!(deno_core::v8_set_flags(vec!["".into(), format!("--stack-size={}", 8 * 1024)]), [""]);
             JsRuntime::init_platform(
                 Some(v8::new_default_platform(0, false).make_shared()),
                 false,
@@ -567,7 +743,13 @@ impl<Ctx: RuntimeContext> Runtime<Ctx> {
             ..Default::default()
         });
 
-        let (is_thunk_symbol, primop_metadata_symbol, has_context_symbol, is_path_symbol) = {
+        let (
+            is_thunk_symbol,
+            primop_metadata_symbol,
+            has_context_symbol,
+            is_path_symbol,
+            is_cycle_symbol,
+        ) = {
             deno_core::scope!(scope, &mut js_runtime);
             Self::get_symbols(scope)?
         };
@@ -578,6 +760,7 @@ impl<Ctx: RuntimeContext> Runtime<Ctx> {
             primop_metadata_symbol,
             has_context_symbol,
             is_path_symbol,
+            is_cycle_symbol,
             _marker: PhantomData,
         })
     }
@@ -605,6 +788,7 @@ impl<Ctx: RuntimeContext> Runtime<Ctx> {
         let primop_metadata_symbol = v8::Local::new(scope, &self.primop_metadata_symbol);
         let has_context_symbol = v8::Local::new(scope, &self.has_context_symbol);
         let is_path_symbol = v8::Local::new(scope, &self.is_path_symbol);
+        let is_cycle_symbol = v8::Local::new(scope, &self.is_cycle_symbol);
 
         Ok(to_value(
             local_value,
@@ -613,10 +797,11 @@ impl<Ctx: RuntimeContext> Runtime<Ctx> {
             primop_metadata_symbol,
             has_context_symbol,
             is_path_symbol,
+            is_cycle_symbol,
         ))
     }
 
-    /// get (IS_THUNK, PRIMOP_METADATA, HAS_CONTEXT, IS_PATH)
+    /// get (IS_THUNK, PRIMOP_METADATA, HAS_CONTEXT, IS_PATH, IS_CYCLE)
     #[allow(clippy::type_complexity)]
     fn get_symbols(
         scope: &ScopeRef,
@@ -625,6 +810,7 @@ impl<Ctx: RuntimeContext> Runtime<Ctx> {
         v8::Global<v8::Symbol>,
         v8::Global<v8::Symbol>,
         v8::Global<v8::Symbol>,
+        v8::Global<v8::Symbol>,
     )> {
         let global = scope.get_current_context().global(scope);
         let nix_key = v8::String::new(scope, "Nix")
@@ -655,8 +841,9 @@ impl<Ctx: RuntimeContext> Runtime<Ctx> {
         let primop_metadata = get_symbol("PRIMOP_METADATA")?;
         let has_context = get_symbol("HAS_CONTEXT")?;
         let is_path = get_symbol("IS_PATH")?;
+        let is_cycle = get_symbol("IS_CYCLE")?;
 
-        Ok((is_thunk, primop_metadata, has_context, is_path))
+        Ok((is_thunk, primop_metadata, has_context, is_path, is_cycle))
     }
 }
 
@@ -667,6 +854,7 @@ fn to_value<'a>(
     primop_metadata_symbol: LocalSymbol<'a>,
     has_context_symbol: LocalSymbol<'a>,
     is_path_symbol: LocalSymbol<'a>,
+    is_cycle_symbol: LocalSymbol<'a>,
 ) -> Value {
     match () {
         _ if val.is_big_int() => {
@@ -703,6 +891,7 @@ fn to_value<'a>(
                         primop_metadata_symbol,
                         has_context_symbol,
                         is_path_symbol,
+                        is_cycle_symbol,
                     )
                 })
                 .collect();
@@ -720,6 +909,10 @@ fn to_value<'a>(
                 return Value::Thunk;
             }
 
+            if is_cycle(val, scope, is_cycle_symbol) {
+                return Value::Repeated;
+            }
+
             if let Some(path_val) = extract_path(val, scope, is_path_symbol) {
                 return Value::Path(path_val);
             }
@@ -749,6 +942,7 @@ fn to_value<'a>(
                             primop_metadata_symbol,
                             has_context_symbol,
                             is_path_symbol,
+                            is_cycle_symbol,
                         ),
                     )
                 })
@@ -768,6 +962,15 @@ fn is_thunk<'a>(val: LocalValue<'a>, scope: &ScopeRef<'a, '_>, symbol: LocalSymb
     matches!(obj.get(scope, symbol.into()), Some(v) if v.is_true())
 }
 
+fn is_cycle<'a>(val: LocalValue<'a>, scope: &ScopeRef<'a, '_>, symbol: LocalSymbol<'a>) -> bool {
+    if !val.is_object() {
+        return false;
+    }
+
+    let obj = val.to_object(scope).expect("infallible conversion");
+    matches!(obj.get(scope, symbol.into()), Some(v) if v.is_true())
+}
+
 fn extract_string_with_context<'a>(
     val: LocalValue<'a>,
     scope: &ScopeRef<'a, '_>,

nix-js/src/value.rs

@@ -35,7 +35,7 @@ impl Display for Symbol {
         if self.normal() {
             write!(f, "{}", self.0)
         } else {
-            write!(f, r#""{}""#, self.0)
+            write!(f, "{}", escape_quote_string(&self.0))
         }
     }
 }
@@ -117,15 +117,27 @@ impl Debug for AttrSet {
 
 impl Display for AttrSet {
     fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
-        use Value::*;
         write!(f, "{{")?;
         for (k, v) in self.data.iter() {
-            write!(f, " {k} = ")?;
+            write!(f, " {k} = {v};")?;
-            match v {
-                List(_) => write!(f, "[ ... ];")?,
-                AttrSet(_) => write!(f, "{{ ... }};")?,
-                v => write!(f, "{v};")?,
         }
+        write!(f, " }}")
+    }
+}
+
+impl AttrSet {
+    pub fn display_compat(&self) -> AttrSetCompatDisplay<'_> {
+        AttrSetCompatDisplay(self)
+    }
+}
+
+pub struct AttrSetCompatDisplay<'a>(&'a AttrSet);
+
+impl Display for AttrSetCompatDisplay<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        write!(f, "{{")?;
+        for (k, v) in self.0.data.iter() {
+            write!(f, " {k} = {};", v.display_compat())?;
         }
         write!(f, " }}")
     }
@@ -159,6 +171,24 @@ impl Display for List {
     }
 }
 
+impl List {
+    pub fn display_compat(&self) -> ListCompatDisplay<'_> {
+        ListCompatDisplay(self)
+    }
+}
+
+pub struct ListCompatDisplay<'a>(&'a List);
+
+impl Display for ListCompatDisplay<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        write!(f, "[ ")?;
+        for v in self.0.data.iter() {
+            write!(f, "{} ", v.display_compat())?;
+        }
+        write!(f, "]")
+    }
+}
+
 /// Represents any possible Nix value that can be returned from an evaluation.
 #[derive(IsVariant, Unwrap, Clone, Debug, PartialEq)]
 pub enum Value {
@@ -191,6 +221,25 @@ pub enum Value {
     Repeated,
 }
 
+fn escape_quote_string(s: &str) -> String {
+    let mut ret = String::with_capacity(s.len() + 2);
+    ret.push('"');
+    let mut iter = s.chars().peekable();
+    while let Some(c) = iter.next() {
+        match c {
+            '\\' => ret.push_str("\\\\"),
+            '"' => ret.push_str("\\\""),
+            '\n' => ret.push_str("\\n"),
+            '\r' => ret.push_str("\\r"),
+            '\t' => ret.push_str("\\t"),
+            '$' if iter.peek() == Some(&'{') => ret.push_str("\\$"),
+            c => ret.push(c),
+        }
+    }
+    ret.push('"');
+    ret
+}
+
 impl Display for Value {
     fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
         use Value::*;
@@ -199,7 +248,7 @@ impl Display for Value {
             &Float(x) => write!(f, "{x}"),
             &Bool(x) => write!(f, "{x}"),
             Null => write!(f, "null"),
-            String(x) => write!(f, r#""{x}""#),
+            String(x) => write!(f, "{}", escape_quote_string(x)),
             Path(x) => write!(f, "{x}"),
             AttrSet(x) => write!(f, "{x}"),
             List(x) => write!(f, "{x}"),
@@ -207,7 +256,36 @@ impl Display for Value {
             Func => write!(f, "«lambda»"),
             PrimOp(name) => write!(f, "«primop {name}»"),
             PrimOpApp(name) => write!(f, "«partially applied primop {name}»"),
-            Repeated => write!(f, "<REPEATED>"),
+            Repeated => write!(f, "«repeated»"),
+        }
+    }
+}
+
+impl Value {
+    pub fn display_compat(&self) -> ValueCompatDisplay<'_> {
+        ValueCompatDisplay(self)
+    }
+}
+
+pub struct ValueCompatDisplay<'a>(&'a Value);
+
+impl Display for ValueCompatDisplay<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        use Value::*;
+        match self.0 {
+            &Int(x) => write!(f, "{x}"),
+            &Float(x) => write!(f, "{x}"),
+            &Bool(x) => write!(f, "{x}"),
+            Null => write!(f, "null"),
+            String(x) => write!(f, "{}", escape_quote_string(x)),
+            Path(x) => write!(f, "{x}"),
+            AttrSet(x) => write!(f, "{}", x.display_compat()),
+            List(x) => write!(f, "{}", x.display_compat()),
+            Thunk => write!(f, "«thunk»"),
+            Func => write!(f, "<LAMBDA>"),
+            PrimOp(_) => write!(f, "<PRIMOP>"),
+            PrimOpApp(_) => write!(f, "<PRIMOP-APP>"),
+            Repeated => write!(f, "«repeated»"),
         }
     }
 }

nix-js/tests/basic_eval.rs

@@ -3,6 +3,8 @@ mod utils;
 use nix_js::value::Value;
 use utils::eval;
 
+use crate::utils::eval_result;
+
 #[test]
 fn arithmetic() {
     assert_eq!(eval("1 + 1"), Value::Int(2));
@@ -63,3 +65,8 @@ fn nested_let() {
         Value::Int(3)
     );
 }
+
+#[test]
+fn rec_inherit_fails() {
+    assert!(eval_result("{ inherit x; }").is_err());
+}

nix-js/tests/derivation.rs

@@ -470,8 +470,8 @@ fn structured_attrs_basic() {
         Value::AttrSet(attrs) => {
             assert!(attrs.contains_key("drvPath"));
             assert!(attrs.contains_key("outPath"));
-            assert!(!attrs.contains_key("foo"));
+            assert!(attrs.contains_key("foo"));
-            assert!(!attrs.contains_key("count"));
+            assert!(attrs.contains_key("count"));
         }
         _ => panic!("Expected AttrSet"),
     }
@@ -492,7 +492,7 @@ fn structured_attrs_nested() {
     match result {
         Value::AttrSet(attrs) => {
             assert!(attrs.contains_key("drvPath"));
-            assert!(!attrs.contains_key("data"));
+            assert!(attrs.contains_key("data"));
         }
         _ => panic!("Expected AttrSet"),
     }
@@ -554,7 +554,7 @@ fn ignore_nulls_true() {
     match result {
         Value::AttrSet(attrs) => {
             assert!(attrs.contains_key("foo"));
-            assert!(!attrs.contains_key("nullValue"));
+            assert!(attrs.contains_key("nullValue"));
         }
         _ => panic!("Expected AttrSet"),
     }
@@ -600,8 +600,8 @@ fn ignore_nulls_with_structured_attrs() {
     match result {
         Value::AttrSet(attrs) => {
             assert!(attrs.contains_key("drvPath"));
-            assert!(!attrs.contains_key("foo"));
+            assert!(attrs.contains_key("foo"));
-            assert!(!attrs.contains_key("nullValue"));
+            assert!(attrs.contains_key("nullValue"));
         }
         _ => panic!("Expected AttrSet"),
     }
@@ -627,8 +627,8 @@ fn all_features_combined() {
             assert!(attrs.contains_key("out"));
             assert!(attrs.contains_key("dev"));
             assert!(attrs.contains_key("outPath"));
-            assert!(!attrs.contains_key("data"));
+            assert!(attrs.contains_key("data"));
-            assert!(!attrs.contains_key("nullValue"));
+            assert!(attrs.contains_key("nullValue"));
         }
         _ => panic!("Expected AttrSet"),
     }
@@ -651,7 +651,7 @@ fn fixed_output_with_structured_attrs() {
         Value::AttrSet(attrs) => {
             assert!(attrs.contains_key("outPath"));
             assert!(attrs.contains_key("drvPath"));
-            assert!(!attrs.contains_key("data"));
+            assert!(attrs.contains_key("data"));
         }
         _ => panic!("Expected AttrSet"),
     }

nix-js/tests/lang.rs

@@ -0,0 +1,348 @@
+#![allow(non_snake_case)]
+
+mod utils;
+
+use std::path::PathBuf;
+
+use nix_js::context::Context;
+use nix_js::error::Source;
+use nix_js::value::Value;
+
+fn get_lang_dir() -> PathBuf {
+    PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("tests/lang")
+}
+
+fn eval_file(name: &str) -> Result<(Value, Source), String> {
+    let lang_dir = get_lang_dir();
+    let nix_path = lang_dir.join(format!("{name}.nix"));
+
+    let expr = format!(r#"import "{}""#, nix_path.display());
+
+    let mut ctx = Context::new().map_err(|e| e.to_string())?;
+    let source = Source {
+        ty: nix_js::error::SourceType::File(nix_path.into()),
+        src: expr.into(),
+    };
+    ctx.eval_code(source.clone())
+        .map(|val| (val, source))
+        .map_err(|e| e.to_string())
+}
+
+fn read_expected(name: &str) -> String {
+    let lang_dir = get_lang_dir();
+    let exp_path = lang_dir.join(format!("{name}.exp"));
+    std::fs::read_to_string(exp_path)
+        .expect("expected file should exist")
+        .trim_end()
+        .to_string()
+}
+
+fn format_value(value: &Value) -> String {
+    value.display_compat().to_string()
+}
+
+macro_rules! eval_okay_test {
+    ($(#[$attr:meta])* $name:ident$(, $pre:expr)?) => {
+        $(#[$attr])*
+        #[test]
+        fn $name() {
+            $(($pre)();)?
+            let test_name = concat!("eval-okay-", stringify!($name))
+                .replace("_", "-")
+                .replace("r#", "");
+            let result = eval_file(&test_name);
+            match result {
+                Ok((value, source)) => {
+                    let actual = format_value(&value);
+                    let actual = actual.replace(
+                        source
+                            .get_dir()
+                            .parent()
+                            .unwrap()
+                            .to_string_lossy()
+                            .as_ref(),
+                        "/pwd",
+                    );
+                    let expected = read_expected(&test_name);
+                    assert_eq!(actual, expected, "Output mismatch for {}", test_name);
+                }
+                Err(e) => {
+                    panic!("Test {} failed to evaluate: {}", test_name, e);
+                }
+            }
+        }
+    };
+}
+
+macro_rules! eval_fail_test {
+    ($name:ident) => {
+        #[test]
+        fn $name() {
+            let test_name = concat!("eval-fail-", stringify!($name))
+                .replace("_", "-")
+                .replace("r#", "");
+            let result = eval_file(&test_name);
+            assert!(
+                result.is_err(),
+                "Test {} should have failed but succeeded with: {:?}",
+                test_name,
+                result
+            );
+        }
+    };
+}
+
+eval_okay_test!(any_all);
+eval_okay_test!(arithmetic);
+eval_okay_test!(attrnames);
+eval_okay_test!(attrs);
+eval_okay_test!(attrs2);
+eval_okay_test!(attrs3);
+eval_okay_test!(attrs4);
+eval_okay_test!(attrs5);
+eval_okay_test!(
+    #[ignore = "__overrides is not supported"]
+    attrs6
+);
+eval_okay_test!(
+    #[ignore = "requires --arg/--argstr CLI flags"]
+    autoargs
+);
+eval_okay_test!(backslash_newline_1);
+eval_okay_test!(backslash_newline_2);
+eval_okay_test!(baseNameOf);
+eval_okay_test!(builtins);
+eval_okay_test!(builtins_add);
+eval_okay_test!(callable_attrs);
+eval_okay_test!(catattrs);
+eval_okay_test!(closure);
+eval_okay_test!(comments);
+eval_okay_test!(concat);
+eval_okay_test!(concatmap);
+eval_okay_test!(concatstringssep);
+eval_okay_test!(context);
+eval_okay_test!(context_introspection);
+eval_okay_test!(
+    #[ignore = "not implemented: convertHash"]
+    convertHash
+);
+eval_okay_test!(curpos);
+eval_okay_test!(deepseq);
+eval_okay_test!(delayed_with);
+eval_okay_test!(delayed_with_inherit);
+eval_okay_test!(deprecate_cursed_or);
+eval_okay_test!(derivation_legacy);
+eval_okay_test!(dynamic_attrs);
+eval_okay_test!(dynamic_attrs_2);
+eval_okay_test!(dynamic_attrs_bare);
+eval_okay_test!(elem);
+eval_okay_test!(empty_args);
+eval_okay_test!(eq);
+eval_okay_test!(eq_derivations);
+eval_okay_test!(filter);
+eval_okay_test!(
+    #[ignore = "not implemented: flakeRefToString"]
+    flake_ref_to_string
+);
+eval_okay_test!(flatten);
+eval_okay_test!(float);
+eval_okay_test!(floor_ceil);
+eval_okay_test!(foldlStrict);
+eval_okay_test!(foldlStrict_lazy_elements);
+eval_okay_test!(foldlStrict_lazy_initial_accumulator);
+eval_okay_test!(fromjson);
+eval_okay_test!(fromjson_escapes);
+eval_okay_test!(
+    #[ignore = "not implemented: fromTOML"]
+    fromTOML
+);
+eval_okay_test!(
+    #[ignore = "not implemented: fromTOML"]
+    fromTOML_timestamps
+);
+eval_okay_test!(functionargs);
+eval_okay_test!(
+    #[ignore = "not implemented: hashFile"]
+    hashfile
+);
+eval_okay_test!(
+    #[ignore = "not implemented: hashString"]
+    hashstring
+);
+eval_okay_test!(getattrpos);
+eval_okay_test!(getattrpos_functionargs);
+eval_okay_test!(getattrpos_undefined);
+eval_okay_test!(getenv, || {
+    unsafe { std::env::set_var("TEST_VAR", "foo") };
+});
+eval_okay_test!(
+    #[ignore = "not implemented: hashString"]
+    groupBy
+);
+eval_okay_test!(r#if);
+eval_okay_test!(ind_string);
+eval_okay_test!(
+    #[ignore = "not implemented: scopedImport"]
+    import
+);
+eval_okay_test!(inherit_attr_pos);
+eval_okay_test!(
+    #[ignore = "__overrides is not supported"]
+    inherit_from
+);
+eval_okay_test!(intersectAttrs);
+eval_okay_test!(r#let);
+eval_okay_test!(list);
+eval_okay_test!(listtoattrs);
+eval_okay_test!(logic);
+eval_okay_test!(map);
+eval_okay_test!(mapattrs);
+eval_okay_test!(merge_dynamic_attrs);
+eval_okay_test!(nested_with);
+eval_okay_test!(new_let);
+eval_okay_test!(null_dynamic_attrs);
+eval_okay_test!(
+    #[ignore = "__overrides is not supported"]
+    overrides
+);
+eval_okay_test!(
+    #[ignore = "not implemented: parseFlakeRef"]
+    parse_flake_ref
+);
+eval_okay_test!(partition);
+eval_okay_test!(path);
+eval_okay_test!(pathexists);
+eval_okay_test!(path_string_interpolation, || {
+    unsafe {
+        std::env::set_var("HOME", "/fake-home");
+    }
+});
+eval_okay_test!(patterns);
+eval_okay_test!(print);
+eval_okay_test!(readDir);
+eval_okay_test!(readfile);
+eval_okay_test!(readFileType);
+eval_okay_test!(redefine_builtin);
+eval_okay_test!(regex_match);
+eval_okay_test!(regex_split);
+eval_okay_test!(regression_20220122);
+eval_okay_test!(regression_20220125);
+eval_okay_test!(regrettable_rec_attrset_merge);
+eval_okay_test!(remove);
+eval_okay_test!(repeated_empty_attrs);
+eval_okay_test!(repeated_empty_list);
+eval_okay_test!(replacestrings);
+eval_okay_test!(
+    #[ignore = "requires -I CLI flags"]
+    search_path
+);
+eval_okay_test!(scope_1);
+eval_okay_test!(scope_2);
+eval_okay_test!(scope_3);
+eval_okay_test!(scope_4);
+eval_okay_test!(scope_6);
+eval_okay_test!(scope_7);
+eval_okay_test!(seq);
+eval_okay_test!(sort);
+eval_okay_test!(splitversion);
+eval_okay_test!(string);
+eval_okay_test!(strings_as_attrs_names);
+eval_okay_test!(substring);
+eval_okay_test!(substring_context);
+eval_okay_test!(symlink_resolution);
+eval_okay_test!(
+    #[ignore = "TCO not implemented, also disabled in CppNix"]
+    tail_call_1
+);
+eval_okay_test!(tojson);
+eval_okay_test!(
+    #[ignore = "not implemented: toXML"]
+    toxml
+);
+eval_okay_test!(
+    #[ignore = "not implemented: toXML"]
+    toxml2
+);
+eval_okay_test!(tryeval);
+eval_okay_test!(types);
+eval_okay_test!(versions);
+eval_okay_test!(with);
+eval_okay_test!(
+    #[ignore = "not implemented: hashString"]
+    zipAttrsWith
+);
+
+eval_fail_test!(fail_abort);
+eval_fail_test!(fail_addDrvOutputDependencies_empty_context);
+eval_fail_test!(fail_addDrvOutputDependencies_multi_elem_context);
+eval_fail_test!(fail_addDrvOutputDependencies_wrong_element_kind);
+eval_fail_test!(fail_addErrorContext_example);
+eval_fail_test!(fail_assert);
+eval_fail_test!(fail_assert_equal_attrs_names);
+eval_fail_test!(fail_assert_equal_attrs_names_2);
+eval_fail_test!(fail_assert_equal_derivations);
+eval_fail_test!(fail_assert_equal_derivations_extra);
+eval_fail_test!(fail_assert_equal_floats);
+eval_fail_test!(fail_assert_equal_function_direct);
+eval_fail_test!(fail_assert_equal_int_float);
+eval_fail_test!(fail_assert_equal_ints);
+eval_fail_test!(fail_assert_equal_list_length);
+eval_fail_test!(fail_assert_equal_paths);
+eval_fail_test!(fail_assert_equal_type);
+eval_fail_test!(fail_assert_equal_type_nested);
+eval_fail_test!(fail_assert_nested_bool);
+eval_fail_test!(fail_attr_name_type);
+eval_fail_test!(fail_attrset_merge_drops_later_rec);
+eval_fail_test!(fail_bad_string_interpolation_1);
+eval_fail_test!(fail_bad_string_interpolation_2);
+eval_fail_test!(fail_bad_string_interpolation_3);
+eval_fail_test!(fail_bad_string_interpolation_4);
+eval_fail_test!(fail_blackhole);
+eval_fail_test!(fail_call_primop);
+eval_fail_test!(fail_deepseq);
+eval_fail_test!(fail_derivation_name);
+eval_fail_test!(fail_dup_dynamic_attrs);
+eval_fail_test!(fail_duplicate_traces);
+eval_fail_test!(fail_eol_1);
+eval_fail_test!(fail_eol_2);
+eval_fail_test!(fail_eol_3);
+eval_fail_test!(fail_fetchTree_negative);
+eval_fail_test!(fail_fetchurl_baseName);
+eval_fail_test!(fail_fetchurl_baseName_attrs);
+eval_fail_test!(fail_fetchurl_baseName_attrs_name);
+eval_fail_test!(fail_flake_ref_to_string_negative_integer);
+eval_fail_test!(fail_foldlStrict_strict_op_application);
+eval_fail_test!(fail_fromJSON_keyWithNullByte);
+eval_fail_test!(fail_fromJSON_overflowing);
+eval_fail_test!(fail_fromJSON_valueWithNullByte);
+eval_fail_test!(fail_fromTOML_keyWithNullByte);
+eval_fail_test!(fail_fromTOML_timestamps);
+eval_fail_test!(fail_fromTOML_valueWithNullByte);
+eval_fail_test!(fail_hashfile_missing);
+eval_fail_test!(fail_infinite_recursion_lambda);
+eval_fail_test!(fail_list);
+eval_fail_test!(fail_missing_arg);
+eval_fail_test!(fail_mutual_recursion);
+eval_fail_test!(fail_nested_list_items);
+eval_fail_test!(fail_nonexist_path);
+eval_fail_test!(fail_not_throws);
+eval_fail_test!(fail_overflowing_add);
+eval_fail_test!(fail_overflowing_div);
+eval_fail_test!(fail_overflowing_mul);
+eval_fail_test!(fail_overflowing_sub);
+eval_fail_test!(fail_path_slash);
+eval_fail_test!(fail_pipe_operators);
+eval_fail_test!(fail_recursion);
+eval_fail_test!(fail_remove);
+eval_fail_test!(fail_scope_5);
+eval_fail_test!(fail_seq);
+eval_fail_test!(fail_set);
+eval_fail_test!(fail_set_override);
+eval_fail_test!(fail_string_nul_1);
+eval_fail_test!(fail_string_nul_2);
+eval_fail_test!(fail_substring);
+eval_fail_test!(fail_toJSON);
+eval_fail_test!(fail_toJSON_non_utf_8);
+eval_fail_test!(fail_to_path);
+eval_fail_test!(fail_undeclared_arg);
+eval_fail_test!(fail_using_set_as_attr_name);

nix-js/tests/lang/data

@@ -0,0 +1 @@
+foo

nix-js/tests/lang/dir1/a.nix

@@ -0,0 +1 @@
+"a"

nix-js/tests/lang/dir2/a.nix

@@ -0,0 +1 @@
+"X"

nix-js/tests/lang/dir2/b.nix

@@ -0,0 +1 @@
+"b"

nix-js/tests/lang/dir3/a.nix

@@ -0,0 +1 @@
+"X"

nix-js/tests/lang/dir3/b.nix

@@ -0,0 +1 @@
+"X"

nix-js/tests/lang/dir3/c.nix

@@ -0,0 +1 @@
+"c"

nix-js/tests/lang/dir4/a.nix

@@ -0,0 +1 @@
+"X"

nix-js/tests/lang/dir4/c.nix

@@ -0,0 +1 @@
+"X"

nix-js/tests/lang/eval-fail-abort.err.exp

@@ -0,0 +1,8 @@
+error:
+       … while calling the 'abort' builtin
+         at /pwd/lang/eval-fail-abort.nix:1:14:
+            1| if true then abort "this should fail" else 1
+             |              ^
+            2|
+
+       error: evaluation aborted with the following error message: 'this should fail'

nix-js/tests/lang/eval-fail-abort.nix

@@ -0,0 +1 @@
+if true then abort "this should fail" else 1

nix-js/tests/lang/eval-fail-addDrvOutputDependencies-empty-context.err.exp

@@ -0,0 +1,8 @@
+error:
+       … while calling the 'addDrvOutputDependencies' builtin
+         at /pwd/lang/eval-fail-addDrvOutputDependencies-empty-context.nix:1:1:
+            1| builtins.addDrvOutputDependencies ""
+             | ^
+            2|
+
+       error: context of string '' must have exactly one element, but has 0

nix-js/tests/lang/eval-fail-addDrvOutputDependencies-empty-context.nix

@@ -0,0 +1 @@
+builtins.addDrvOutputDependencies ""

nix-js/tests/lang/eval-fail-addDrvOutputDependencies-multi-elem-context.err.exp

@@ -0,0 +1,9 @@
+error:
+       … while calling the 'addDrvOutputDependencies' builtin
+         at /pwd/lang/eval-fail-addDrvOutputDependencies-multi-elem-context.nix:25:1:
+           24| in
+           25| builtins.addDrvOutputDependencies combo-path
+             | ^
+           26|
+
+       error: context of string '/nix/store/pg9yqs4yd85yhdm3f4i5dyaqp5jahrsz-fail.drv/nix/store/2dxd5frb715z451vbf7s8birlf3argbk-fail-2.drv' must have exactly one element, but has 2

nix-js/tests/lang/eval-fail-addDrvOutputDependencies-multi-elem-context.nix

@@ -0,0 +1,25 @@
+let
+  drv0 = derivation {
+    name = "fail";
+    builder = "/bin/false";
+    system = "x86_64-linux";
+    outputs = [
+      "out"
+      "foo"
+    ];
+  };
+
+  drv1 = derivation {
+    name = "fail-2";
+    builder = "/bin/false";
+    system = "x86_64-linux";
+    outputs = [
+      "out"
+      "foo"
+    ];
+  };
+
+  combo-path = "${drv0.drvPath}${drv1.drvPath}";
+
+in
+builtins.addDrvOutputDependencies combo-path

nix-js/tests/lang/eval-fail-addDrvOutputDependencies-wrong-element-kind.err.exp

@@ -0,0 +1,9 @@
+error:
+       … while calling the 'addDrvOutputDependencies' builtin
+         at /pwd/lang/eval-fail-addDrvOutputDependencies-wrong-element-kind.nix:13:1:
+           12| in
+           13| builtins.addDrvOutputDependencies drv.outPath
+             | ^
+           14|
+
+       error: `addDrvOutputDependencies` can only act on derivations, not on a derivation output such as 'out'

nix-js/tests/lang/eval-fail-addDrvOutputDependencies-wrong-element-kind.nix

@@ -0,0 +1,13 @@
+let
+  drv = derivation {
+    name = "fail";
+    builder = "/bin/false";
+    system = "x86_64-linux";
+    outputs = [
+      "out"
+      "foo"
+    ];
+  };
+
+in
+builtins.addDrvOutputDependencies drv.outPath

nix-js/tests/lang/eval-fail-addErrorContext-example.err.exp

@@ -0,0 +1,24 @@
+error:
+       … while counting down; n = 10
+
+       … while counting down; n = 9
+
+       … while counting down; n = 8
+
+       … while counting down; n = 7
+
+       … while counting down; n = 6
+
+       … while counting down; n = 5
+
+       … while counting down; n = 4
+
+       … while counting down; n = 3
+
+       … while counting down; n = 2
+
+       … while counting down; n = 1
+
+       (stack trace truncated; use '--show-trace' to show the full, detailed trace)
+
+       error: kaboom

nix-js/tests/lang/eval-fail-addErrorContext-example.nix

@@ -0,0 +1,9 @@
+let
+  countDown =
+    n:
+    if n == 0 then
+      throw "kaboom"
+    else
+      builtins.addErrorContext "while counting down; n = ${toString n}" ("x" + countDown (n - 1));
+in
+countDown 10

nix-js/tests/lang/eval-fail-assert-equal-attrs-names-2.err.exp

@@ -0,0 +1,8 @@
+error:
+       … while evaluating the condition of the assertion '({ a = true; } == { a = true; b = true; })'
+         at /pwd/lang/eval-fail-assert-equal-attrs-names-2.nix:1:1:
+            1| assert
+             | ^
+            2|   {
+
+       error: attribute names of attribute set '{ a = true; }' differs from attribute set '{ a = true; b = true; }'

nix-js/tests/lang/eval-fail-assert-equal-attrs-names-2.nix

@@ -0,0 +1,8 @@
+assert
+  {
+    a = true;
+  } == {
+    a = true;
+    b = true;
+  };
+throw "unreachable"

nix-js/tests/lang/eval-fail-assert-equal-attrs-names.err.exp

@@ -0,0 +1,8 @@
+error:
+       … while evaluating the condition of the assertion '({ a = true; b = true; } == { a = true; })'
+         at /pwd/lang/eval-fail-assert-equal-attrs-names.nix:1:1:
+            1| assert
+             | ^
+            2|   {
+
+       error: attribute names of attribute set '{ a = true; b = true; }' differs from attribute set '{ a = true; }'

nix-js/tests/lang/eval-fail-assert-equal-attrs-names.nix

@@ -0,0 +1,8 @@
+assert
+  {
+    a = true;
+    b = true;
+  } == {
+    a = true;
+  };
+throw "unreachable"

nix-js/tests/lang/eval-fail-assert-equal-derivations-extra.err.exp

@@ -0,0 +1,26 @@
+error:
+       … while evaluating the condition of the assertion '({ foo = { outPath = "/nix/store/0"; type = "derivation"; }; } == { foo = { devious = true; outPath = "/nix/store/1"; type = "derivation"; }; })'
+         at /pwd/lang/eval-fail-assert-equal-derivations-extra.nix:1:1:
+            1| assert
+             | ^
+            2|   {
+
+       … while comparing attribute 'foo'
+
+       … where left hand side is
+         at /pwd/lang/eval-fail-assert-equal-derivations-extra.nix:3:5:
+            2|   {
+            3|     foo = {
+             |     ^
+            4|       type = "derivation";
+
+       … where right hand side is
+         at /pwd/lang/eval-fail-assert-equal-derivations-extra.nix:8:5:
+            7|   } == {
+            8|     foo = {
+             |     ^
+            9|       type = "derivation";
+
+       … while comparing a derivation by its 'outPath' attribute
+
+       error: string '"/nix/store/0"' is not equal to string '"/nix/store/1"'

nix-js/tests/lang/eval-fail-assert-equal-derivations-extra.nix

@@ -0,0 +1,14 @@
+assert
+  {
+    foo = {
+      type = "derivation";
+      outPath = "/nix/store/0";
+    };
+  } == {
+    foo = {
+      type = "derivation";
+      outPath = "/nix/store/1";
+      devious = true;
+    };
+  };
+throw "unreachable"

nix-js/tests/lang/eval-fail-assert-equal-derivations.err.exp

@@ -0,0 +1,26 @@
+error:
+       … while evaluating the condition of the assertion '({ foo = { ignored = (abort "not ignored"); outPath = "/nix/store/0"; type = "derivation"; }; } == { foo = { ignored = (abort "not ignored"); outPath = "/nix/store/1"; type = "derivation"; }; })'
+         at /pwd/lang/eval-fail-assert-equal-derivations.nix:1:1:
+            1| assert
+             | ^
+            2|   {
+
+       … while comparing attribute 'foo'
+
+       … where left hand side is
+         at /pwd/lang/eval-fail-assert-equal-derivations.nix:3:5:
+            2|   {
+            3|     foo = {
+             |     ^
+            4|       type = "derivation";
+
+       … where right hand side is
+         at /pwd/lang/eval-fail-assert-equal-derivations.nix:9:5:
+            8|   } == {
+            9|     foo = {
+             |     ^
+           10|       type = "derivation";
+
+       … while comparing a derivation by its 'outPath' attribute
+
+       error: string '"/nix/store/0"' is not equal to string '"/nix/store/1"'

nix-js/tests/lang/eval-fail-assert-equal-derivations.nix

@@ -0,0 +1,15 @@
+assert
+  {
+    foo = {
+      type = "derivation";
+      outPath = "/nix/store/0";
+      ignored = abort "not ignored";
+    };
+  } == {
+    foo = {
+      type = "derivation";
+      outPath = "/nix/store/1";
+      ignored = abort "not ignored";
+    };
+  };
+throw "unreachable"

nix-js/tests/lang/eval-fail-assert-equal-floats.err.exp

@@ -0,0 +1,22 @@
+error:
+       … while evaluating the condition of the assertion '({ b = 1; } == { b = 1.01; })'
+         at /pwd/lang/eval-fail-assert-equal-floats.nix:1:1:
+            1| assert { b = 1.0; } == { b = 1.01; };
+             | ^
+            2| abort "unreachable"
+
+       … while comparing attribute 'b'
+
+       … where left hand side is
+         at /pwd/lang/eval-fail-assert-equal-floats.nix:1:10:
+            1| assert { b = 1.0; } == { b = 1.01; };
+             |          ^
+            2| abort "unreachable"
+
+       … where right hand side is
+         at /pwd/lang/eval-fail-assert-equal-floats.nix:1:26:
+            1| assert { b = 1.0; } == { b = 1.01; };
+             |                          ^
+            2| abort "unreachable"
+
+       error: a float with value '1' is not equal to a float with value '1.01'

nix-js/tests/lang/eval-fail-assert-equal-floats.nix

@@ -0,0 +1,2 @@
+assert { b = 1.0; } == { b = 1.01; };
+abort "unreachable"

nix-js/tests/lang/eval-fail-assert-equal-function-direct.err.exp

@@ -0,0 +1,9 @@
+error:
+       … while evaluating the condition of the assertion '((x: x) == (x: x))'
+         at /pwd/lang/eval-fail-assert-equal-function-direct.nix:3:1:
+            2| # This only compares a direct comparison and makes no claims about functions in nested structures.
+            3| assert (x: x) == (x: x);
+             | ^
+            4| abort "unreachable"
+
+       error: distinct functions and immediate comparisons of identical functions compare as unequal

nix-js/tests/lang/eval-fail-assert-equal-function-direct.nix

@@ -0,0 +1,4 @@
+# Note: functions in nested structures, e.g. attributes, may be optimized away by pointer identity optimization.
+# This only compares a direct comparison and makes no claims about functions in nested structures.
+assert (x: x) == (x: x);
+abort "unreachable"

nix-js/tests/lang/eval-fail-assert-equal-int-float.err.exp

@@ -0,0 +1,8 @@
+error:
+       … while evaluating the condition of the assertion '(1 == 1.1)'
+         at /pwd/lang/eval-fail-assert-equal-int-float.nix:1:1:
+            1| assert 1 == 1.1;
+             | ^
+            2| throw "unreachable"
+
+       error: an integer with value '1' is not equal to a float with value '1.1'

nix-js/tests/lang/eval-fail-assert-equal-int-float.nix

@@ -0,0 +1,2 @@
+assert 1 == 1.1;
+throw "unreachable"

nix-js/tests/lang/eval-fail-assert-equal-ints.err.exp

@@ -0,0 +1,22 @@
+error:
+       … while evaluating the condition of the assertion '({ b = 1; } == { b = 2; })'
+         at /pwd/lang/eval-fail-assert-equal-ints.nix:1:1:
+            1| assert { b = 1; } == { b = 2; };
+             | ^
+            2| abort "unreachable"
+
+       … while comparing attribute 'b'
+
+       … where left hand side is
+         at /pwd/lang/eval-fail-assert-equal-ints.nix:1:10:
+            1| assert { b = 1; } == { b = 2; };
+             |          ^
+            2| abort "unreachable"
+
+       … where right hand side is
+         at /pwd/lang/eval-fail-assert-equal-ints.nix:1:24:
+            1| assert { b = 1; } == { b = 2; };
+             |                        ^
+            2| abort "unreachable"
+
+       error: an integer with value '1' is not equal to an integer with value '2'

nix-js/tests/lang/eval-fail-assert-equal-ints.nix

@@ -0,0 +1,2 @@
+assert { b = 1; } == { b = 2; };
+abort "unreachable"

nix-js/tests/lang/eval-fail-assert-equal-list-length.err.exp

@@ -0,0 +1,8 @@
+error:
+       … while evaluating the condition of the assertion '([ (1) (0) ] == [ (10) ])'
+         at /pwd/lang/eval-fail-assert-equal-list-length.nix:1:1:
+            1| assert
+             | ^
+            2|   [
+
+       error: list of size '2' is not equal to list of size '1', left hand side is '[ 1 0 ]', right hand side is '[ 10 ]'

nix-js/tests/lang/eval-fail-assert-equal-list-length.nix

@@ -0,0 +1,6 @@
+assert
+  [
+    1
+    0
+  ] == [ 10 ];
+throw "unreachable"

nix-js/tests/lang/eval-fail-assert-equal-paths.err.exp

@@ -0,0 +1,8 @@
+error:
+       … while evaluating the condition of the assertion '(/pwd/lang/foo == /pwd/lang/bar)'
+         at /pwd/lang/eval-fail-assert-equal-paths.nix:1:1:
+            1| assert ./foo == ./bar;
+             | ^
+            2| throw "unreachable"
+
+       error: path '/pwd/lang/foo' is not equal to path '/pwd/lang/bar'

nix-js/tests/lang/eval-fail-assert-equal-paths.nix

@@ -0,0 +1,2 @@
+assert ./foo == ./bar;
+throw "unreachable"

nix-js/tests/lang/eval-fail-assert-equal-type-nested.err.exp

@@ -0,0 +1,22 @@
+error:
+       … while evaluating the condition of the assertion '({ ding = false; } == { ding = null; })'
+         at /pwd/lang/eval-fail-assert-equal-type-nested.nix:1:1:
+            1| assert { ding = false; } == { ding = null; };
+             | ^
+            2| abort "unreachable"
+
+       … while comparing attribute 'ding'
+
+       … where left hand side is
+         at /pwd/lang/eval-fail-assert-equal-type-nested.nix:1:10:
+            1| assert { ding = false; } == { ding = null; };
+             |          ^
+            2| abort "unreachable"
+
+       … where right hand side is
+         at /pwd/lang/eval-fail-assert-equal-type-nested.nix:1:31:
+            1| assert { ding = false; } == { ding = null; };
+             |                               ^
+            2| abort "unreachable"
+
+       error: a Boolean of value 'false' is not equal to null of value 'null'

nix-js/tests/lang/eval-fail-assert-equal-type-nested.nix

@@ -0,0 +1,2 @@
+assert { ding = false; } == { ding = null; };
+abort "unreachable"

nix-js/tests/lang/eval-fail-assert-equal-type.err.exp

@@ -0,0 +1,8 @@
+error:
+       … while evaluating the condition of the assertion '(false == null)'
+         at /pwd/lang/eval-fail-assert-equal-type.nix:1:1:
+            1| assert false == null;
+             | ^
+            2| abort "unreachable"
+
+       error: a Boolean of value 'false' is not equal to null of value 'null'

nix-js/tests/lang/eval-fail-assert-equal-type.nix

@@ -0,0 +1,2 @@
+assert false == null;
+abort "unreachable"

nix-js/tests/lang/eval-fail-assert-nested-bool.err.exp

@@ -0,0 +1,66 @@
+error:
+       … while evaluating the condition of the assertion '({ a = { b = [ ({ c = { d = true; }; }) ]; }; } == { a = { b = [ ({ c = { d = false; }; }) ]; }; })'
+         at /pwd/lang/eval-fail-assert-nested-bool.nix:1:1:
+            1| assert { a.b = [ { c.d = true; } ]; } == { a.b = [ { c.d = false; } ]; };
+             | ^
+            2|
+
+       … while comparing attribute 'a'
+
+       … where left hand side is
+         at /pwd/lang/eval-fail-assert-nested-bool.nix:1:10:
+            1| assert { a.b = [ { c.d = true; } ]; } == { a.b = [ { c.d = false; } ]; };
+             |          ^
+            2|
+
+       … where right hand side is
+         at /pwd/lang/eval-fail-assert-nested-bool.nix:1:44:
+            1| assert { a.b = [ { c.d = true; } ]; } == { a.b = [ { c.d = false; } ]; };
+             |                                            ^
+            2|
+
+       … while comparing attribute 'b'
+
+       … where left hand side is
+         at /pwd/lang/eval-fail-assert-nested-bool.nix:1:10:
+            1| assert { a.b = [ { c.d = true; } ]; } == { a.b = [ { c.d = false; } ]; };
+             |          ^
+            2|
+
+       … where right hand side is
+         at /pwd/lang/eval-fail-assert-nested-bool.nix:1:44:
+            1| assert { a.b = [ { c.d = true; } ]; } == { a.b = [ { c.d = false; } ]; };
+             |                                            ^
+            2|
+
+       … while comparing list element 0
+
+       … while comparing attribute 'c'
+
+       … where left hand side is
+         at /pwd/lang/eval-fail-assert-nested-bool.nix:1:20:
+            1| assert { a.b = [ { c.d = true; } ]; } == { a.b = [ { c.d = false; } ]; };
+             |                    ^
+            2|
+
+       … where right hand side is
+         at /pwd/lang/eval-fail-assert-nested-bool.nix:1:54:
+            1| assert { a.b = [ { c.d = true; } ]; } == { a.b = [ { c.d = false; } ]; };
+             |                                                      ^
+            2|
+
+       … while comparing attribute 'd'
+
+       … where left hand side is
+         at /pwd/lang/eval-fail-assert-nested-bool.nix:1:20:
+            1| assert { a.b = [ { c.d = true; } ]; } == { a.b = [ { c.d = false; } ]; };
+             |                    ^
+            2|
+
+       … where right hand side is
+         at /pwd/lang/eval-fail-assert-nested-bool.nix:1:54:
+            1| assert { a.b = [ { c.d = true; } ]; } == { a.b = [ { c.d = false; } ]; };
+             |                                                      ^
+            2|
+
+       error: boolean 'true' is not equal to boolean 'false'

nix-js/tests/lang/eval-fail-assert-nested-bool.nix

@@ -0,0 +1,3 @@
+assert { a.b = [ { c.d = true; } ]; } == { a.b = [ { c.d = false; } ]; };
+
+abort "unreachable"

nix-js/tests/lang/eval-fail-assert.err.exp

@@ -0,0 +1,30 @@
+error:
+       … while evaluating the attribute 'body'
+         at /pwd/lang/eval-fail-assert.nix:7:3:
+            6|
+            7|   body = x "x";
+             |   ^
+            8| }
+
+       … from call site
+         at /pwd/lang/eval-fail-assert.nix:7:10:
+            6|
+            7|   body = x "x";
+             |          ^
+            8| }
+
+       … while calling 'x'
+         at /pwd/lang/eval-fail-assert.nix:3:5:
+            2|   x =
+            3|     arg:
+             |     ^
+            4|     assert arg == "y";
+
+       … while evaluating the condition of the assertion '(arg == "y")'
+         at /pwd/lang/eval-fail-assert.nix:4:5:
+            3|     arg:
+            4|     assert arg == "y";
+             |     ^
+            5|     123;
+
+       error: string '"x"' is not equal to string '"y"'

nix-js/tests/lang/eval-fail-assert.nix

@@ -0,0 +1,8 @@
+let {
+  x =
+    arg:
+    assert arg == "y";
+    123;
+
+  body = x "x";
+}

nix-js/tests/lang/eval-fail-attr-name-type.err.exp

@@ -0,0 +1,21 @@
+error:
+       … while evaluating the attribute 'puppy."${key}"'
+         at /pwd/lang/eval-fail-attr-name-type.nix:3:5:
+            2|   attrs = {
+            3|     puppy.doggy = { };
+             |     ^
+            4|   };
+
+       … while evaluating an attribute name
+         at /pwd/lang/eval-fail-attr-name-type.nix:7:15:
+            6| in
+            7| attrs.puppy.${key}
+             |               ^
+            8|
+
+       error: expected a string but found an integer: 1
+       at /pwd/lang/eval-fail-attr-name-type.nix:7:15:
+            6| in
+            7| attrs.puppy.${key}
+             |               ^
+            8|

nix-js/tests/lang/eval-fail-attr-name-type.nix

@@ -0,0 +1,7 @@
+let
+  attrs = {
+    puppy.doggy = { };
+  };
+  key = 1;
+in
+attrs.puppy.${key}

nix-js/tests/lang/eval-fail-attrset-merge-drops-later-rec.err.exp

@@ -0,0 +1,6 @@
+error: undefined variable 'd'
+       at /pwd/lang/eval-fail-attrset-merge-drops-later-rec.nix:4:9:
+            3|   a = rec {
+            4|     c = d + 2;
+             |         ^
+            5|     d = 3;

nix-js/tests/lang/eval-fail-attrset-merge-drops-later-rec.nix

@@ -0,0 +1,8 @@
+{
+  a.b = 1;
+  a = rec {
+    c = d + 2;
+    d = 3;
+  };
+}
+.c

nix-js/tests/lang/eval-fail-bad-string-interpolation-1.err.exp

@@ -0,0 +1,8 @@
+error:
+       … while evaluating a path segment
+         at /pwd/lang/eval-fail-bad-string-interpolation-1.nix:1:2:
+            1| "${x: x}"
+             |  ^
+            2|
+
+       error: cannot coerce a function to a string: «lambda @ /pwd/lang/eval-fail-bad-string-interpolation-1.nix:1:4»

nix-js/tests/lang/eval-fail-bad-string-interpolation-1.nix

@@ -0,0 +1 @@
+"${x: x}"

nix-js/tests/lang/eval-fail-bad-string-interpolation-2.err.exp

@@ -0,0 +1 @@
+error: path '/pwd/lang/fnord' does not exist

nix-js/tests/lang/eval-fail-bad-string-interpolation-2.nix

@@ -0,0 +1 @@
+"${./fnord}"

nix-js/tests/lang/eval-fail-bad-string-interpolation-3.err.exp

@@ -0,0 +1,8 @@
+error:
+       … while evaluating a path segment
+         at /pwd/lang/eval-fail-bad-string-interpolation-3.nix:1:3:
+            1| ''${x: x}''
+             |   ^
+            2|
+
+       error: cannot coerce a function to a string: «lambda @ /pwd/lang/eval-fail-bad-string-interpolation-3.nix:1:5»

nix-js/tests/lang/eval-fail-bad-string-interpolation-3.nix

@@ -0,0 +1 @@
+''${x: x}''

nix-js/tests/lang/eval-fail-bad-string-interpolation-4.err.exp

@@ -0,0 +1,9 @@
+error:
+       … while evaluating a path segment
+         at /pwd/lang/eval-fail-bad-string-interpolation-4.nix:19:3:
+           18| # The error message should not be too long.
+           19| ''${pkgs}''
+             |   ^
+           20|
+
+       error: cannot coerce a set to a string: { a = { a = { a = { a = "ha"; b = "ha"; c = "ha"; d = "ha"; e = "ha"; f = "ha"; g = "ha"; h = "ha"; j = "ha"; }; «8 attributes elided» }; «8 attributes elided» }; «8 attributes elided» }

nix-js/tests/lang/eval-fail-bad-string-interpolation-4.nix

@@ -0,0 +1,19 @@
+let
+  # Basically a "billion laughs" attack, but toned down to simulated `pkgs`.
+  ha = x: y: {
+    a = x y;
+    b = x y;
+    c = x y;
+    d = x y;
+    e = x y;
+    f = x y;
+    g = x y;
+    h = x y;
+    j = x y;
+  };
+  has = ha (ha (ha (ha (x: x)))) "ha";
+  # A large structure that has already been evaluated.
+  pkgs = builtins.deepSeq has has;
+in
+# The error message should not be too long.
+''${pkgs}''

nix-js/tests/lang/eval-fail-blackhole.err.exp

@@ -0,0 +1,14 @@
+error:
+       … while evaluating the attribute 'body'
+         at /pwd/lang/eval-fail-blackhole.nix:2:3:
+            1| let {
+            2|   body = x;
+             |   ^
+            3|   x = y;
+
+       error: infinite recursion encountered
+       at /pwd/lang/eval-fail-blackhole.nix:3:7:
+            2|   body = x;
+            3|   x = y;
+             |       ^
+            4|   y = x;

nix-js/tests/lang/eval-fail-blackhole.nix

@@ -0,0 +1,5 @@
+let {
+  body = x;
+  x = y;
+  y = x;
+}

nix-js/tests/lang/eval-fail-call-primop.err.exp

@@ -0,0 +1,10 @@
+error:
+       … while calling the 'length' builtin
+         at /pwd/lang/eval-fail-call-primop.nix:1:1:
+            1| builtins.length 1
+             | ^
+            2|
+
+       … while evaluating the first argument passed to builtins.length
+
+       error: expected a list but found an integer: 1