René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Bug in fileHandle.readableWebStream implementation","articleBody":"### Version\n\nv24.2.0\n\n### Platform\n\n```text\nDarwin mac.igd.fraunhofer.de 24.5.0 Darwin Kernel Version 24.5.0: Tue Apr 22 19:54:25 PDT 2025; root:xnu-11417.121.6~2/RELEASE_ARM64_T6020 arm64\n```\n\n### Subsystem\n\n_No response_\n\n### What steps will reproduce the bug?\n\nStart the attached script.\n\n[bug.zip](https://github.com/user-attachments/files/20888817/bug.zip)\n\n```mjs\n#!/usr/bin/env node\n\nimport * as fsPromises from 'node:fs/promises';\n\nconst scriptURL = new URL(import.meta.url);\nconst fileHandle = await fsPromises.open(scriptURL);\nconst readableStream = fileHandle.readableWebStream();\nconst reader = readableStream.getReader({ mode: \"byob\" });\nconst arrayBuffer = new ArrayBuffer(3);\nconst view = new Uint8Array(arrayBuffer, 2, 1);\nconst result = await reader.read(view);\n```\n\n### How often does it reproduce? Is there a required condition?\n\nAlways.\n\n### What is the expected behavior? Why is that the expected behavior?\n\nI do not expect to get an exception.\n\n### What do you see instead?\n\nI do get the following exception:\n\n```\nnode:internal/fs/promises:689\n  validateOffsetLengthRead(offset, length, buffer.byteLength);\n  ^\n\nRangeError [ERR_OUT_OF_RANGE]: The value of \"length\" is out of range. It must be \u003c= -1. Received 1\n    at read (node:internal/fs/promises:689:3)\n    at fsCall (node:internal/fs/promises:467:18)\n    at FileHandle.read (node:internal/fs/promises:199:12)\n    at Object.pull (node:internal/fs/promises:322:37)\n    at invokePromiseCallback (node:internal/webstreams/util:172:10)\n    at Object.\u003canonymous> (node:internal/webstreams/util:177:23)\n    at readableByteStreamControllerCallPullIfNeeded (node:internal/webstreams/readablestream:3145:24)\n    at node:internal/webstreams/readablestream:3295:7 {\n  code: 'ERR_OUT_OF_RANGE'\n}\n\nNode.js v24.2.0\n```\n\n### Additional information\n\nThere seems to be a bug in line 321 of \"node/lib/internal/fs/promises.js\". The line currently looks like this:\n\n```\nconst { bytesRead } = await readFn(view, view.byteOffset, view.byteLength);\n```\n\nIt probably should look like this:\n\n```\nconst { bytesRead } = await readFn(view, 0, view.byteLength);\n```\n\nYou want to read to offset 0 of the Uint8Array \"view\", not to the byteOffset of its underlying ArrayBuffer.\n\nI'm not able to test this fix (I cannot build node.js myself).","author":{"url":"https://github.com/pdaehne","@type":"Person","name":"pdaehne"},"datePublished":"2025-06-24T17:49:45Z","url":"https://github.com/nodejs/node/issues/58817"}