René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"stream/iter: pipeTo() crashes when synchronous writev() returns undefined","articleBody":"### Version\n\n26.2.0\n\n### Platform\n\n```text\nmacOS 26.5.0\n```\n\n### Subsystem\n\nstream\n\n### What steps will reproduce the bug?\n\n```js\nimport { pipeTo } from 'node:stream/iter';\n\nasync function* source() {\n  yield [new Uint8Array([65]), new Uint8Array([66])];\n}\n\nconst chunks = [];\nconst writer = {\n  write(chunk) {\n    chunks.push(chunk);\n  },\n  writev(batch) {\n    chunks.push(...batch);\n    // Synchronous success: returns undefined.\n  },\n  end() {},\n};\n\ntry {\n  const bytes = await pipeTo(source(), writer);\n  console.log('resolved:', bytes, Buffer.concat(chunks).toString());\n} catch (err) {\n  console.log('rejected:', `${err.name}: ${err.message}`);\n}\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\n```console\nresolved: 2 AB\n```\n\n### What do you see instead?\n\n```console\nrejected: TypeError: Method Promise.prototype.then called on incompatible receiver undefined\n```\n\npiping into a custom writer that supports batched writes fails even though the writer successfully accepts the data synchronously. The same kind of synchronous success works for single writes, so batched `writev()` writes should complete normally instead of rejecting with a `TypeError`.\n\n### Additional information\n\n_No response_","author":{"url":"https://github.com/trivikr","@type":"Person","name":"trivikr"},"datePublished":"2026-05-25T16:05:17.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/63560/node/issues/63560"}