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doc: clarify transform._transform() callback argument logic #48680

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merged 1 commit into from
Jul 8, 2023

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rafasofizada
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Edited / fixed version of #48653

Clarified that stream.Transform callback second argument is passed only if the first argument is null, 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 an Error. I was implementing a truncation stream, and passed both an Error ("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 not null.

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.

Clarify that `transform._transform()` callback second argument is
used only if the first argument is `null`, i.e. no error occured
processing the chunk.
@nodejs-github-bot nodejs-github-bot added doc Issues and PRs related to the documentations. stream Issues and PRs related to the stream subsystem. labels Jul 6, 2023
@lpinca lpinca added the commit-queue Add this label to land a pull request using GitHub Actions. label Jul 8, 2023
@nodejs-github-bot nodejs-github-bot removed the commit-queue Add this label to land a pull request using GitHub Actions. label Jul 8, 2023
@nodejs-github-bot nodejs-github-bot merged commit eece8d7 into nodejs:main Jul 8, 2023
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juanarbol pushed a commit that referenced this pull request Jul 13, 2023
Clarify that `transform._transform()` callback second argument is
used only if the first argument is `null`, i.e. no error occured
processing the chunk.

PR-URL: #48680
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Akhil Marsonya <akhil.marsonya27@gmail.com>
@juanarbol juanarbol mentioned this pull request Jul 13, 2023
Ceres6 pushed a commit to Ceres6/node that referenced this pull request Aug 14, 2023
Clarify that `transform._transform()` callback second argument is
used only if the first argument is `null`, i.e. no error occured
processing the chunk.

PR-URL: nodejs#48680
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Akhil Marsonya <akhil.marsonya27@gmail.com>
Ceres6 pushed a commit to Ceres6/node that referenced this pull request Aug 14, 2023
Clarify that `transform._transform()` callback second argument is
used only if the first argument is `null`, i.e. no error occured
processing the chunk.

PR-URL: nodejs#48680
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Akhil Marsonya <akhil.marsonya27@gmail.com>
ruyadorno pushed a commit that referenced this pull request Sep 11, 2023
Clarify that `transform._transform()` callback second argument is
used only if the first argument is `null`, i.e. no error occured
processing the chunk.

PR-URL: #48680
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Akhil Marsonya <akhil.marsonya27@gmail.com>
@ruyadorno ruyadorno mentioned this pull request Sep 11, 2023
ruyadorno pushed a commit that referenced this pull request Sep 13, 2023
Clarify that `transform._transform()` callback second argument is
used only if the first argument is `null`, i.e. no error occured
processing the chunk.

PR-URL: #48680
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Akhil Marsonya <akhil.marsonya27@gmail.com>
ruyadorno pushed a commit that referenced this pull request Sep 17, 2023
Clarify that `transform._transform()` callback second argument is
used only if the first argument is `null`, i.e. no error occured
processing the chunk.

PR-URL: #48680
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Akhil Marsonya <akhil.marsonya27@gmail.com>
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4 participants