René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"assert: ERR_INVALID_ARG_TYPE on failing assert(value) under --enable-source-maps (v26 regression)","articleBody":"### Version\n\nv26.1.0\n\n### Platform\n\n```text\n\n```\n\n### Subsystem\n\nassert\n\n### What steps will reproduce the bug?\n\nSave the following as `repro.mjs`:\n\n```js\nimport { strict as assert } from 'node:assert';\n\ntry {\n  assert(false);\n} catch (e) {\n  console.log(e.constructor.name, e.code, JSON.stringify(e.message));\n}\n```\n\nRun it under Node.js v26.0.0 or later, with and without `--enable-source-maps`:\n\n```console\n$ node repro.mjs\nAssertionError ERR_ASSERTION \"The expression evaluated to a falsy value:\\n\\n  assert(false)\\n\"\n\n$ node --enable-source-maps repro.mjs\nTypeError ERR_INVALID_ARG_TYPE \"The \\\"message\\\" argument must be one of type string or function. Received undefined\"\n```\n\nThe same `TypeError` is thrown for `assert.ok(false)` and `assert.strict(false)`. It does not appear for `assert.equal`, `assert.strictEqual`, and so on — only the auto-generated-message path used by `assert(value)` / `assert.ok(value)` is affected.\n\nThe same script on Node.js v25.9.0 (with `--enable-source-maps`) prints `AssertionError` as expected.\n\n\n### How often does it reproduce? Is there a required condition?\n\n100%. The required conditions are:\n\n1. Node.js v26.0.0 or v26.1.0\n2. `--enable-source-maps` is enabled.\n3. The script that performs the assertion has no source map registered for it.\n4. A failing `assert(value)` or `assert.ok(value)` is executed without an explicit `message` argument.\n\n### What is the expected behavior? Why is that the expected behavior?\n\nThe same as Node.js v25.x: a failing `assert(value)` should throw an `AssertionError` instead of throwing a `TypeError`.\n\n### What do you see instead?\n\nA `TypeError [ERR_INVALID_ARG_TYPE]: The \"message\" argument must be one of type string or function. Received undefined` is thrown from inside `internal/assert/utils.js`, before any `AssertionError` is constructed:\n\n```\nTypeError [ERR_INVALID_ARG_TYPE]: The \"message\" argument must be one of type string or function. Received undefined\n    at innerFail (node:internal/assert/utils:135:11)\n    at innerOk (node:internal/assert/utils:169:5)\n    at strict (node:assert:882:3)\n    ...\n```\n\n\n### Additional information\n\nWhen `--enable-source-maps` is on but no source map is registered for the script (typical for a hand-written `.mjs` / `.cjs` file), `getErrorSourceLocation` in `lib/internal/errors/error_source.js` returns `undefined`, then `getErrMessage` in `lib/internal/assert/utils.js` returns `undefined`, then `innerOk` passes `[undefined]` to the new strict `innerFail`, and `innerFail` throws `ERR_INVALID_ARG_TYPE`.","author":{"url":"https://github.com/twada","@type":"Person","name":"twada"},"datePublished":"2026-05-07T13:56:36Z","url":"https://github.com/nodejs/node/issues/63169"}