feat: lookup path (builtins.findFile)

Cargo.lock

@@ -1927,11 +1927,11 @@ dependencies = [
  "rnix",
  "rowan",
  "rusqlite",
+ "rust-embed",
  "rustyline",
  "serde",
  "serde_json",
  "sha2",
- "sourcemap",
  "string-interner",
  "tar",
  "tempfile",
@@ -2587,6 +2587,40 @@ dependencies = [
  "smallvec",
 ]
 
+[[package]]
+name = "rust-embed"
+version = "8.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "04113cb9355a377d83f06ef1f0a45b8ab8cd7d8b1288160717d66df5c7988d27"
+dependencies = [
+ "rust-embed-impl",
+ "rust-embed-utils",
+ "walkdir",
+]
+
+[[package]]
+name = "rust-embed-impl"
+version = "8.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "da0902e4c7c8e997159ab384e6d0fc91c221375f6894346ae107f47dd0f3ccaa"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "rust-embed-utils",
+ "syn",
+ "walkdir",
+]
+
+[[package]]
+name = "rust-embed-utils"
+version = "8.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5bcdef0be6fe7f6fa333b1073c949729274b05f123a0ad7efcb8efd878e5c3b1"
+dependencies = [
+ "sha2",
+ "walkdir",
+]
+
 [[package]]
 name = "rustc-demangle"
 version = "0.1.27"

nix-js/Cargo.toml

@@ -30,6 +30,8 @@ hashbrown = "0.16"
 petgraph = "0.8"
 string-interner = "0.19"
 
+rust-embed="8.11"
+
 itertools = "0.14"
 
 regex = "1.11"
@@ -41,7 +43,6 @@ nix-nar = "0.3"
 sha2 = "0.10"
 hex = "0.4"
 
-sourcemap = "9.0"
 base64 = "0.22"
 
 # Fetcher dependencies

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

@@ -8,7 +8,7 @@ import { force } from "../thunk";
 import { type NixStringContext, mkStringWithContext, addBuiltContext } from "../string-context";
 import { forceFunction } from "../type-assert";
 import { nixValueToJson } from "../conversion";
-import { typeOf } from "./type-check";
+import { isAttrs, isPath, typeOf } from "./type-check";
 
 const convertJsonToNix = (json: unknown): NixValue => {
   if (json === null) {
@@ -283,6 +283,16 @@ export const coerceToStringWithContext = (
  * - Preserves string context if present
  */
 export const coerceToPath = (value: NixValue, outContext?: NixStringContext): string => {
+  const forced = force(value);
+
+  if (isPath(forced)) {
+    return forced.value;
+  }
+  if (isAttrs(forced) && Object.hasOwn(forced, "__toString")) {
+    const toStringFunc = forceFunction(forced.__toString);
+    return coerceToPath(toStringFunc(forced), outContext);
+  }
+
   const pathStr = coerceToString(value, StringCoercionMode.Base, false, outContext);
 
   if (pathStr === "") {

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

@@ -3,15 +3,16 @@
  * Implemented via Rust ops exposed through deno_core
  */
 
-import { forceAttrs, forceBool, forceStringValue } from "../type-assert";
-import type { NixValue, NixAttrs } from "../types";
-import { isNixPath } from "../types";
+import { forceAttrs, forceBool, forceList, forceStringNoCtx, forceStringValue } from "../type-assert";
+import type { NixValue, NixAttrs, NixPath } from "../types";
+import { isNixPath, IS_PATH, CatchableError } from "../types";
 import { force } from "../thunk";
 import { coerceToPath, coerceToString, StringCoercionMode } from "./conversion";
 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";
 
 export const importFunc = (path: NixValue): NixValue => {
   const context: NixStringContext = new Set();
@@ -390,10 +391,70 @@ export const filterSource = (args: NixValue): never => {
   throw new Error("Not implemented: filterSource");
 };
 
+const suffixIfPotentialMatch = (prefix: string, path: string): string | null => {
+  const n = prefix.length;
+
+  const needSeparator = n > 0 && n < path.length;
+
+  if (needSeparator && path[n] !== "/") {
+    return null;
+  }
+
+  if (!path.startsWith(prefix)) {
+    return null;
+  }
+
+  return needSeparator ? path.substring(n + 1) : path.substring(n);
+};
+
 export const findFile =
-  (search: NixValue) =>
-  (lookup: NixValue): never => {
-    throw new Error("Not implemented: findFile");
+  (searchPath: NixValue) =>
+  (lookupPath: NixValue): NixPath => {
+    const forcedSearchPath = forceList(searchPath);
+    const lookupPathStr = forceStringNoCtx(lookupPath);
+
+    for (const item of forcedSearchPath) {
+      const attrs = forceAttrs(item);
+
+      const prefix = "prefix" in attrs ? forceStringNoCtx(attrs.prefix) : "";
+
+      if (!("path" in attrs)) {
+        throw new Error("findFile: search path element is missing 'path' attribute");
+      }
+
+      const suffix = suffixIfPotentialMatch(prefix, lookupPathStr);
+      if (suffix === null) {
+        continue;
+      }
+
+      const context: NixStringContext = new Set();
+      const pathVal = coerceToString(attrs.path, StringCoercionMode.Interpolation, false, context);
+
+      if (context.size > 0) {
+        throw new Error("findFile: path with string context is not yet supported");
+      }
+
+      const resolvedPath = Deno.core.ops.op_resolve_path(pathVal, "");
+      const candidatePath = suffix.length > 0
+        ? Deno.core.ops.op_resolve_path(suffix, resolvedPath)
+        : resolvedPath;
+
+      if (Deno.core.ops.op_path_exists(candidatePath)) {
+        return { [IS_PATH]: true, value: candidatePath };
+      }
+    }
+
+    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/${corepkgName}>` };
+      }
+    }
+
+    throw new CatchableError(`file '${lookupPathStr}' was not found in the Nix search path`);
   };
 
 export const getEnv = (s: NixValue): string => {

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

@@ -0,0 +1,73 @@
+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

@@ -0,0 +1,9 @@
+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

@@ -169,7 +169,15 @@ export const concatStringsWithContext = (parts: NixValue[]): NixString | NixPath
  * @returns NixPath object with absolute path
  */
 export const resolvePath = (currentDir: string, path: NixValue): NixPath => {
-  const pathStr = forceStringValue(path);
+  const forced = force(path);
+  let pathStr: string;
+
+  if (isNixPath(forced)) {
+    pathStr = forced.value;
+  } else {
+    pathStr = forceStringValue(path);
+  }
+
   const resolved = Deno.core.ops.op_resolve_path(currentDir, pathStr);
   return mkPath(resolved);
 };

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

@@ -85,6 +85,17 @@ export const forceString = (value: NixValue): NixString => {
   throw new TypeError(`Expected string, got ${typeOf(forced)}`);
 };
 
+export const forceStringNoCtx = (value: NixValue): string => {
+  const forced = force(value);
+  if (typeof forced === "string") {
+    return forced;
+  }
+  if (isStringWithContext(forced)) {
+    throw new TypeError(`the string '${forced.value}' is not allowed to refer to a store path`)
+  }
+  throw new TypeError(`Expected string, got ${typeOf(forced)}`);
+}
+
 /**
  * Force a value and assert it's a boolean
  * @throws TypeError if value is not a boolean after forcing

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

@@ -5,7 +5,7 @@
 import { force, IS_THUNK } from "./thunk";
 import { type StringWithContext, HAS_CONTEXT, isStringWithContext, getStringContext } from "./string-context";
 import { op } from "./operators";
-import { forceAttrs } from "./type-assert";
+import { forceAttrs, forceStringNoCtx } from "./type-assert";
 import { isString, typeOf } from "./builtins/type-check";
 export { HAS_CONTEXT, isStringWithContext };
 export type { StringWithContext };
@@ -81,13 +81,8 @@ export const mkAttrs = (attrs: NixAttrs, keys: NixValue[], values: NixValue[]):
     if (key === null) {
       continue;
     }
-    if (!isString(key)) {
-      throw `Expected string, got ${typeOf(key)}`
-    }
-    if (isStringWithContext(key)) {
-      throw new TypeError(`the string '${key.value}' is not allowed to refer to a store path`)
-    }
-    attrs[key] = values[i];
+    const str = forceStringNoCtx(key);
+    attrs[str] = values[i];
   }
   return attrs;
 };

nix-js/src/ir/downgrade.rs

@@ -103,7 +103,19 @@ impl<Ctx: DowngradeContext> Downgrade<Ctx> for ast::Path {
             .collect::<Result<Vec<_>>>()?;
 
         let expr = if parts.len() == 1 {
-            parts.into_iter().next().unwrap()
+            let part = parts.into_iter().next().unwrap();
+            if let &Ir::Str(Str { ref val, span }) = ctx.get_ir(part)
+                && let Some(path) = val.strip_prefix("<").map(|path| &path[..path.len() - 1]) {
+                ctx.replace_ir(part, Str { val: path.to_string(), span }.to_ir());
+                let sym = ctx.new_sym("findFile".into());
+                let find_file = ctx.new_expr(Builtin { inner: sym, span }.to_ir());
+                let sym = ctx.new_sym("nixPath".into());
+                let nix_path = ctx.new_expr(Builtin { inner: sym, span }.to_ir());
+                let call = ctx.new_expr(Call { func: find_file, arg: nix_path, span }.to_ir());
+                return Ok(ctx.new_expr(Call { func: call, arg: part, span }.to_ir()));
+            } else {
+                part
+            }
         } else {
             ctx.new_expr(ConcatStrings { parts, span }.to_ir())
         };

nix-js/src/runtime.rs

@@ -1,11 +1,12 @@
 use std::borrow::Cow;
 use std::marker::PhantomData;
 use std::path::{Component, Path, PathBuf};
-use std::sync::Once;
+use std::sync::{Arc, Once};
 
 use deno_core::{Extension, ExtensionFileSource, JsRuntime, OpState, RuntimeOptions, v8};
 use deno_error::JsErrorClass;
 use itertools::Itertools as _;
+use rust_embed::Embed;
 
 use crate::error::{Error, Result, Source};
 use crate::store::Store;
@@ -96,6 +97,10 @@ mod private {
 }
 pub(crate) use private::NixError;
 
+#[derive(Embed)]
+#[folder = "src/runtime/corepkgs"]
+pub(crate) struct CorePkgs;
+
 #[deno_core::op2]
 #[string]
 fn op_import<Ctx: RuntimeContext>(
@@ -105,6 +110,24 @@ fn op_import<Ctx: RuntimeContext>(
     let _span = tracing::info_span!("op_import", path = %path).entered();
     let ctx: &mut Ctx = state.get_ctx_mut();
 
+    // FIXME: special path type
+    if path.starts_with("<nix/") && path.ends_with(">") {
+        let corepkg_name = &path[5..path.len() - 1];
+        if let Some(file) = CorePkgs::get(corepkg_name) {
+            tracing::info!("Importing corepkg: {}", corepkg_name);
+            let source = Source {
+                ty: crate::error::SourceType::Eval(Arc::new(ctx.get_current_dir().to_path_buf())),
+                src: str::from_utf8(&file.data)
+                    .expect("corrupted corepkgs file")
+                    .into(),
+            };
+            ctx.add_source(source.clone());
+            return Ok(ctx.compile_code(source).map_err(|err| err.to_string())?);
+        } else {
+            return Err(format!("Corepkg not found: {}", corepkg_name).into());
+        }
+    }
+
     let current_dir = ctx.get_current_dir();
     let mut absolute_path = current_dir
         .join(&path)

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

@@ -0,0 +1,76 @@
+{
+  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),
+  # still translates to __impure to trigger derivationStrict error checks.
+  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;
+
+    impureEnvVars = [
+      # We borrow these environment variables from the caller to allow
+      # easy proxy configuration.  This is impure, but a fixed-output
+      # derivation like fetchurl is allowed to do so since its result is
+      # by definition pure.
+      "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/tests/findfile.rs

@@ -0,0 +1,38 @@
+mod utils;
+
+use utils::eval;
+
+#[test]
+fn test_find_file_corepkg_fetchurl() {
+    let result = eval(
+        r#"
+        let
+          searchPath = [];
+          lookupPath = "nix/fetchurl.nix";
+        in
+          builtins.findFile searchPath lookupPath
+        "#,
+    );
+
+    assert!(result.to_string().contains("fetchurl.nix"));
+}
+
+#[test]
+fn test_lookup_path_syntax() {
+    let result = eval(r#"<nix/fetchurl.nix>"#);
+    assert!(result.to_string().contains("fetchurl.nix"));
+}
+
+#[test]
+fn test_import_corepkg() {
+    let result = eval(
+        r#"
+        let
+          fetchurl = import <nix/fetchurl.nix>;
+        in
+          builtins.typeOf fetchurl
+        "#,
+    );
+
+    assert_eq!(result.to_string(), "\"lambda\"");
+}