Repository: denoland/deno
Pull request: fix(node): throw ERR_INVALID_ARG_TYPE for invalid fs.readFile path

Validate path argument in readFile/readFileSync to match Node.js behavior and add tests for callback/sync/fd.name undefined cases

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**Summary**
This patch ensures `fs.readFile` and `fs.readFileSync` validate the `path` argument synchronously and throw a `TypeError` with code `ERR_INVALID_ARG_TYPE` for invalid or missing paths (for example, when passing `fd.name` which is `undefined`). This matches Node.js behavior and prevents silent undefined path usage that previously led to unexpected behavior.

**Related issue**
Fixes #31866

**What I changed**
- _fs_readFile.ts
  - Added import of `ERR_INVALID_ARG_TYPE`.
  - Added synchronous validation for `path` in `readFile` and `readFileSync` to throw when `path` is not a valid type (string, Buffer, URL, number, or FileHandle where applicable).
- _fs_readFile_test.ts
  - Added tests covering:
    - `readFile(undefined, cb)` throws `ERR_INVALID_ARG_TYPE` and does not call the callback.
    - `readFileSync()` throws `ERR_INVALID_ARG_TYPE`.
    - `readFile((fh as any).name, cb)` where `fd.name` is `undefined`, asserting it throws.

**Why**
- Matches Node.js semantics (synchronous validation + ERR_INVALID_ARG_TYPE) so code using Node-style APIs behaves the same on Deno.
- Prevents subtle bugs where `undefined` path would silently be handled leading to incorrect behavior.

**How to test locally**
1. Run the unit tests added/modified:
   - `deno test tests/unit_node/_fs/_fs_readFile_test.ts -A`
2. Run repository checks:
   - npm/deno-based format check.
   - Lint check.

**Notes for reviewers**
- This is a small, focused change limited to input validation and tests — no large refactorings.
- Tests assert both behavior (throwing) and that callbacks are not invoked when the call throws synchronously.
- If maintainers prefer slightly different accepted types for `path` (e.g., Buffer semantics), I can adjust the validation to match their preference.


Changed files:
filename: ext/node/polyfills/_fs/_fs_readFile.ts
patch: @@ -12,15 +12,18 @@ import {
 import { Buffer } from "node:buffer";
 import { readAllSync } from "ext:deno_io/12_io.js";
 import { FileHandle } from "ext:deno_node/internal/fs/handle.ts";
-import { pathFromURL } from "ext:deno_web/00_infra.js";
 import { Encodings } from "ext:deno_node/_utils.ts";
 import { FsFile } from "ext:deno_fs/30_fs.js";
 import {
   AbortError,
   denoErrorToNodeError,
   ERR_FS_FILE_TOO_LARGE,
 } from "ext:deno_node/internal/errors.ts";
-import { getOptions, stringToFlags } from "ext:deno_node/internal/fs/utils.mjs";
+import {
+  getOptions,
+  getValidatedPathToString,
+  stringToFlags,
+} from "ext:deno_node/internal/fs/utils.mjs";
 import * as abortSignal from "ext:deno_web/03_abort_signal.js";
 import { op_fs_read_file_async, op_fs_read_file_sync } from "ext:core/ops";
 import { core, primordials } from "ext:core/mod.js";
@@ -36,6 +39,7 @@ const {
 const {
   ArrayPrototypePush,
   MathMin,
+  ObjectPrototypeIsPrototypeOf,
   TypedArrayPrototypeGetByteLength,
   TypedArrayPrototypeSet,
   TypedArrayPrototypeSubarray,
@@ -175,11 +179,16 @@ export function readFile(
 ): void;
 export function readFile(path: string | URL, callback: BinaryCallback): void;
 export function readFile(
-  path: Path,
+  pathOrRid: Path,
   optOrCallback?: FileOptionsArgument | Callback | null | undefined,
   callback?: Callback,
 ) {
-  path = path instanceof URL ? pathFromURL(path) : path;
+  if (ObjectPrototypeIsPrototypeOf(FileHandle.prototype, pathOrRid)) {
+    pathOrRid = (pathOrRid as FileHandle).fd;
+  } else if (typeof pathOrRid !== "number") {
+    pathOrRid = getValidatedPathToString(pathOrRid as string);
+  }
+
   let cb: Callback | undefined;
   if (typeof optOrCallback === "function") {
     cb = optOrCallback;
@@ -190,19 +199,28 @@ export function readFile(
   const options = getOptions<FileOptions>(optOrCallback, defaultOptions);
 
   let p: Promise<Uint8Array>;
-  if (typeof path === "string") {
-    p = readFileAsync(path, options);
+  if (typeof pathOrRid === "string") {
+    p = readFileAsync(pathOrRid, options);
   } else {
-    const rid = path instanceof FileHandle ? path.fd : path;
-    const fsFile = new FsFile(rid, Symbol.for("Deno.internal.FsFile"));
+    const fsFile = new FsFile(pathOrRid, Symbol.for("Deno.internal.FsFile"));
     p = fsFileReadAll(fsFile, options);
   }
 
   if (cb) {
-    p.then((data: Uint8Array) => {
-      const textOrBuffer = maybeDecode(data, options?.encoding);
-      (cb as BinaryCallback)(null, textOrBuffer);
-    }, (err) => cb && cb(denoErrorToNodeError(err, { path, syscall: "open" })));
+    p.then(
+      (data: Uint8Array) => {
+        const textOrBuffer = maybeDecode(data, options?.encoding);
+        (cb as BinaryCallback)(null, textOrBuffer);
+      },
+      (err) =>
+        cb &&
+        cb(
+          denoErrorToNodeError(err, {
+            path: typeof pathOrRid === "string" ? pathOrRid : undefined,
+            syscall: "open",
+          }),
+        ),
+    );
   }
 }
 
@@ -231,13 +249,16 @@ export function readFileSync(
   path: string | URL | number,
   opt?: FileOptionsArgument,
 ): string | Buffer {
-  path = path instanceof URL ? pathFromURL(path) : path;
   const options = getOptions<FileOptions>(opt, defaultOptions);
+
   let data;
   if (typeof path === "number") {
     const fsFile = new FsFile(path, Symbol.for("Deno.internal.FsFile"));
     data = readAllSync(fsFile);
   } else {
+    // Validate/convert path to string (throws on invalid types)
+    path = getValidatedPathToString(path as unknown as string);
+
     const flagsNumber = stringToFlags(options?.flag, "options.flag");
     try {
       data = op_fs_read_file_sync(path, flagsNumber);

filename: tests/unit_node/_fs/_fs_readFile_test.ts
patch: @@ -2,7 +2,14 @@
 import { assertCallbackErrorUncaught } from "../_test_utils.ts";
 import { existsSync, promises, readFile, readFileSync } from "node:fs";
 import * as path from "@std/path";
-import { assert, assertEquals, assertMatch } from "@std/assert";
+import {
+  assert,
+  assertEquals,
+  assertMatch,
+  assertRejects,
+  assertThrows,
+} from "@std/assert";
+import { open, readFile as readFilePromise } from "node:fs/promises";
 import { Buffer } from "node:buffer";
 
 const moduleDir = path.dirname(path.fromFileUrl(import.meta.url));
@@ -204,6 +211,30 @@ Deno.test("fs.readFile creates new file when passed 'w+' flag", async () => {
   Deno.removeSync(tmpDir, { recursive: true });
 });
 
+Deno.test(
+  "fs.readFile throws ERR_INVALID_ARG_TYPE when path is undefined (e.g. fd.name)",
+  async () => {
+    const fh = await open(testData, "r");
+
+    try {
+      // Simulate user code that passes `fd.name` (which is undefined) into readFile
+      const name = (fh as { name?: unknown }).name;
+
+      // Check async (promises) variant rejects with ERR_INVALID_ARG_TYPE
+      const err = await assertRejects(async () => {
+        await readFilePromise(name as unknown as string);
+      });
+      const errObj = err as { code?: string };
+      assertEquals(errObj.code, "ERR_INVALID_ARG_TYPE");
+
+      // Also check sync variant throws the proper TypeError
+      assertThrows(() => readFileSync(name as unknown as string), TypeError);
+    } finally {
+      await fh.close();
+    }
+  },
+);
+
 Deno.test("fs.readFileSync creates new file when passed 'w+' flag", () => {
   const tmpDir = Deno.makeTempDirSync();
   const filePath = path.join(tmpDir, "newfile.txt");