doc: clarified stream.Transform callback argument logic #48653
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lpinca
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Jul 6, 2023
doc/api/stream.md
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| @@ -4517,7 +4517,8 @@ The `callback` function must be called only when the current chunk is completely | |||
| consumed. The first argument passed to the `callback` must be an `Error` object | |||
| if an error occurred while processing the input or `null` otherwise. If a second | |||
| argument is passed to the `callback`, it will be forwarded on to the | |||
| `transform.push()` method. In other words, the following are equivalent: | |||
| `transform.push()` method, but only if the first argument is `null`. In other | |||
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| `transform.push()` method, but only if the first argument is `null`. In other | |
| `transform.push()` method, but only if the first argument is falsy. In other |
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@lpinca thanks for the approval! Could you please advice how would I go about editing the commit message to pass the lint-commit-message check? |
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Wrap the commit message body to 72 chars per line. Also use an imperative verb for commit message title (clarified -> clarify). |
Clarify that streamTransform callback second argument is passed only if the first argument is `null`, i.e. no error occured processing the chunk.
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Clarified that
stream.Transformcallback second argument is passed only if the first argument isnull, i.e. no error occured processing the chunk.From the way the documentation is written right now, I expected the second argument to be forwarded to
transform.push(), even if the first argument is anError. I was implementing a truncation stream, and passed both anError("stream exceeded maximum size"; could be optionally caught and ignored), and the last (truncated) chunk. Only after digging through the relevant implementaton I could confirm for sure that the second argument is entirely ignored if the first one is notnull.Please tell me if you want to adjust the wording somehow, or whether I should add an alternative example to the one following the line "In other words, the following are equivalent:". Hopefully you'll find this useful.