fix: infinite recursion on perl (WIP)

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}}'

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

@@ -351,6 +351,18 @@ export const derivationStrict = (args: NixValue): NixAttrs => {
   return result;
 };
 
+const specialAttrs = new Set([
+  "name",
+  "builder",
+  "system",
+  "args",
+  "outputs",
+  "__structuredAttrs",
+  "__ignoreNulls",
+  "__contentAddressed",
+  "impure",
+]);
+
 export const derivation = (args: NixValue): NixAttrs => {
   const attrs = forceAttrs(args);
   const strict = derivationStrict(args);
@@ -364,18 +376,6 @@ export const derivation = (args: NixValue): NixAttrs => {
   const ignoreNulls = "__ignoreNulls" in attrs ? force(attrs.__ignoreNulls) === true : false;
   const drvArgs = extractArgs(attrs, collectedContext);
 
-  const specialAttrs = new Set([
-    "name",
-    "builder",
-    "system",
-    "args",
-    "outputs",
-    "__structuredAttrs",
-    "__ignoreNulls",
-    "__contentAddressed",
-    "impure",
-  ]);
-
   const baseAttrs: NixAttrs = {
     type: "derivation",
     drvPath: strict.drvPath,

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

@@ -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 =
@@ -452,13 +461,8 @@ 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/misc.ts

@@ -2,7 +2,7 @@
  * Miscellaneous builtin functions
  */
 
-import { createThunk, force } from "../thunk";
+import { force } from "../thunk";
 import { CatchableError } from "../types";
 import type { NixAttrs, NixBool, NixStrictValue, NixValue } from "../types";
 import { forceList, forceAttrs, forceFunction, forceStringValue, forceString, forceStringNoCtx } from "../type-assert";
@@ -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;
   };
 

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();
@@ -183,7 +180,7 @@ 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 [${path}]` : "while selecting attribute";
@@ -229,7 +226,7 @@ export const selectWithDefault = (
   default_val: NixValue,
   span?: string,
 ): NixValue => {
-  if (STACK_TRACE.enabled && span) {
+  if (span) {
     const pathStrings = attrpath.map((a) => forceStringValue(a));
     const path = pathStrings.join(".");
     const message = path ? `while selecting attribute [${path}]` : "while selecting attribute";
@@ -337,7 +334,7 @@ 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

@@ -14,7 +14,6 @@ import {
   concatStringsWithContext,
   call,
   assert,
-  STACK_TRACE,
   pushContext,
   popContext,
   withContext,
@@ -41,7 +40,6 @@ export const Nix = {
   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/thunk.ts

@@ -12,8 +12,9 @@ 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 +98,29 @@ 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();
     }
+  }
 };
 
 /**

nix-js/src/codegen.rs

@@ -11,9 +11,6 @@ pub(crate) fn compile(expr: &Ir, ctx: &impl CodegenContext) -> String {
     if std::env::var("NIX_JS_DEBUG_THUNKS").is_ok() {
         debug_flags.push("Nix.DEBUG_THUNKS.enabled=true");
     }
-    if std::env::var("NIX_JS_STACK_TRACE").is_ok() {
-        debug_flags.push("Nix.STACK_TRACE.enabled=true");
-    }
     let debug_prefix = if debug_flags.is_empty() {
         String::new()
     } else {
@@ -97,17 +94,11 @@ impl<Ctx: CodegenContext> Compile<Ctx> for Ir {
                 let cond_code = ctx.get_ir(cond).compile(ctx);
                 let consq = ctx.get_ir(consq).compile(ctx);
                 let alter = ctx.get_ir(alter).compile(ctx);
-
-                // Only add context tracking if STACK_TRACE is enabled
-                if std::env::var("NIX_JS_STACK_TRACE").is_ok() {
                 let cond_span = encode_span(ctx.get_ir(cond).span(), ctx);
                 format!(
                     "(Nix.withContext(\"while evaluating a branch condition\",{},()=>Nix.forceBool({})))?({}):({})",
                     cond_span, cond_code, consq, alter
                 )
-                } else {
-                    format!("Nix.forceBool({cond_code})?({consq}):({alter})")
-                }
             }
             Ir::BinOp(x) => x.compile(ctx),
             Ir::UnOp(x) => x.compile(ctx),
@@ -149,9 +140,6 @@ impl<Ctx: CodegenContext> Compile<Ctx> for Ir {
             }) => {
                 let assertion_code = ctx.get_ir(assertion).compile(ctx);
                 let expr = ctx.get_ir(expr).compile(ctx);
-
-                // Only add context tracking if STACK_TRACE is enabled
-                if std::env::var("NIX_JS_STACK_TRACE").is_ok() {
                 let assertion_span = encode_span(ctx.get_ir(assertion).span(), ctx);
                 let span = encode_span(span, ctx);
                 format!(
@@ -162,14 +150,6 @@ impl<Ctx: CodegenContext> Compile<Ctx> for Ir {
                     assertion_raw.escape_quote(),
                     span
                 )
-                } else {
-                    format!(
-                        "Nix.assert({},{},{})",
-                        assertion_code,
-                        expr,
-                        assertion_raw.escape_quote()
-                    )
-                }
             }
             Ir::CurPos(cur_pos) => {
                 let span_str = encode_span(cur_pos.span, ctx);
@@ -186,20 +166,12 @@ impl<Ctx: CodegenContext> Compile<Ctx> for BinOp {
         let lhs = ctx.get_ir(self.lhs).compile(ctx);
         let rhs = ctx.get_ir(self.rhs).compile(ctx);
 
-        // Only add context tracking if STACK_TRACE is enabled
-        let stack_trace_enabled = std::env::var("NIX_JS_STACK_TRACE").is_ok();
-
-        // Helper to wrap operation with context (only if enabled)
         let with_ctx = |op_name: &str, op_call: String| {
-            if stack_trace_enabled {
             let span = encode_span(self.span, ctx);
             format!(
                 "Nix.withContext(\"while evaluating the {} operator\",{},()=>({}))",
                 op_name, span, op_call
             )
-            } else {
-                op_call
-            }
         };
 
         match self.kind {
@@ -308,13 +280,9 @@ impl<Ctx: CodegenContext> Compile<Ctx> for Let {
         let info = &self.binding_sccs;
         let mut js_statements = Vec::new();
 
-        for (scc_exprs, is_recursive) in info.sccs.iter() {
+        for (scc_exprs, _is_recursive) in info.sccs.iter() {
             for &expr in scc_exprs {
-                let value = if *is_recursive {
+                let value = unwrap_thunk(ctx.get_ir(expr), ctx);
-                    ctx.get_ir(expr).compile(ctx)
-                } else {
-                    unwrap_thunk(ctx.get_ir(expr), ctx)
-                };
                 js_statements.push(format!("const expr{}={}", expr.0, value));
             }
         }
@@ -351,21 +319,16 @@ impl<Ctx: CodegenContext> Compile<Ctx> for AttrSet {
     fn compile(&self, ctx: &Ctx) -> String {
         let mut attrs = Vec::new();
         let mut attr_positions = Vec::new();
-        let stack_trace_enabled = std::env::var("NIX_JS_STACK_TRACE").is_ok();
 
         for (&sym, &(expr, attr_span)) in &self.stcs {
             let key = ctx.get_sym(sym);
             let value_code = ctx.get_ir(expr).compile(ctx);
 
-            let value = if stack_trace_enabled {
             let value_span = encode_span(ctx.get_ir(expr).span(), ctx);
-                format!(
+            let value = format!(
                 "Nix.withContext(\"while evaluating the attribute '{}'\",{},()=>({}))",
                 key, value_span, value_code
-                )
+            );
-            } else {
-                value_code
-            };
             attrs.push(format!("{}:{}", key.escape_quote(), value));
 
             let attr_pos_str = encode_span(attr_span, ctx);
@@ -381,15 +344,11 @@ impl<Ctx: CodegenContext> Compile<Ctx> for AttrSet {
                     let val_expr = ctx.get_ir(*val);
                     let val = val_expr.compile(ctx);
                     let span = val_expr.span();
-                    let val = if stack_trace_enabled {
                     let span = encode_span(span, ctx);
-                        format!(
+                    let val = format!(
                         "Nix.withContext(\"while evaluating a dynamic attribute\",{},()=>({}))",
                         span, val
-                        )
+                    );
-                    } else {
-                        val
-                    };
                     let dyn_span_str = encode_span(*attr_span, ctx);
                     (key, val, dyn_span_str)
                 })
@@ -416,23 +375,17 @@ impl<Ctx: CodegenContext> Compile<Ctx> for AttrSet {
 
 impl<Ctx: CodegenContext> Compile<Ctx> for List {
     fn compile(&self, ctx: &Ctx) -> String {
-        let stack_trace_enabled = std::env::var("NIX_JS_STACK_TRACE").is_ok();
-
         let list = self
             .items
             .iter()
             .enumerate()
             .map(|(idx, item)| {
                 let item_code = ctx.get_ir(*item).compile(ctx);
-                if stack_trace_enabled {
                 let item_span = encode_span(ctx.get_ir(*item).span(), ctx);
                 format!(
                     "Nix.withContext(\"while evaluating list element {}\",{},()=>({}))",
                     idx, item_span, item_code
                 )
-                } else {
-                    item_code
-                }
             })
             .join(",");
         format!("[{list}]")
@@ -441,22 +394,16 @@ impl<Ctx: CodegenContext> Compile<Ctx> for List {
 
 impl<Ctx: CodegenContext> Compile<Ctx> for ConcatStrings {
     fn compile(&self, ctx: &Ctx) -> String {
-        let stack_trace_enabled = std::env::var("NIX_JS_STACK_TRACE").is_ok();
-
         let parts: Vec<String> = self
             .parts
             .iter()
             .map(|part| {
                 let part_code = ctx.get_ir(*part).compile(ctx);
-                if stack_trace_enabled {
                 let part_span = encode_span(ctx.get_ir(*part).span(), ctx);
                 format!(
                     "Nix.withContext(\"while evaluating a path segment\",{},()=>({}))",
                     part_span, part_code
                 )
-                } else {
-                    part_code
-                }
             })
             .collect();
 

nix-js/src/error.rs

@@ -214,8 +214,8 @@ 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 +234,11 @@ 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 +276,7 @@ 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/utils.rs

@@ -314,7 +314,8 @@ where
                 ctx.set_current_binding(Some(slot));
 
                 let default = if let Some(default) = default {
-                    Some(default.clone().downgrade(ctx)?)
+                    let default = default.clone().downgrade(ctx)?;
+                    Some(ctx.maybe_thunk(default))
                 } else {
                     None
                 };