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stream: fix stream.finished on Duplex #33133

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@ronag ronag commented Apr 28, 2020

finished would incorrectly believe that a Duplex is already
closed if either the readable or writable side has completed.

Fixes: #33130

Checklist
  • make -j4 test (UNIX), or vcbuild test (Windows) passes
  • tests and/or benchmarks are included
  • documentation is changed or added
  • commit message follows commit guidelines

finished would incorrectly believe that a Duplex is already
closed if either the readable or writable side has completed.

Fixes: nodejs#33130
@ronag ronag added the stream Issues and PRs related to the stream subsystem. label Apr 28, 2020
@ronag ronag requested a review from mcollina April 28, 2020 17:38
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ronag commented Apr 28, 2020

@nodejs/streams @mafintosh @szmarczak

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ronag commented Apr 28, 2020

fast-track?

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@ronag You need to delay the write to response, so the readable event is emitted after the finish one. See the gist above.

@addaleax addaleax added the fast-track PRs that do not need to wait for 48 hours to land. label Apr 28, 2020
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lgtm

(wState && wState.errorEmitted) || (rState && rState.errorEmitted) ||
(wState && wState.finished) || (rState && rState.endEmitted) ||
(rState && stream.req && stream.aborted);
const closed = (
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Can we simplify this a bit? Perhaps at the very least group together similar dependencies, like:

const closed = (
  (wState && (wState.closed || wState.errorEmitted)) ||
  (rState && (rState.closed || rState.errorEmitted || (stream.req && stream.aborted))) ||
  (
    (!writable || (wState && wState.finished)) &&
    (!readable || (rState && rState.endEmitted))
  )
);

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@ronag ronag Apr 29, 2020

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They are grouped? See below.

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Unless there is a performance benefit to the above suggestion, I prefer @ronag's grouping because it's easier to read. Though it has more lines, it has less parentheses and the lines are ordered by the properties (e.g. closed) of the states. It reads like "is either state closed, or either state errorEmitted, or ..".

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I have not personally benchmarked it, so I cannot say if it is measurable or not. However, it is reducing the number of duplicate checks so V8 should be performing less work.

However, my code suggestion was merely one possibility. I'm not opposed to rearranging the checks in other ways, such as introducing separate if statements, etc.

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I prefer the current formatting and believe any performance implication here would be negligible in practice. This is not a hot path as far as I'm aware. A future simplification could be to use the ?. operator.

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nodejs-github-bot commented Apr 29, 2020


if (closed) {
// TODO(ronag): Re-throw error if errorEmitted?
// TODO(ronag): Throw premature close as if finished was called?
// before being closed? i.e. if closed but not errored, ended or finished.
// TODO(ronag): Throw some kind of error? Does it make sense
// to call finished() on a "finished" stream?
// TODO(ronag): willEmitClose?
process.nextTick(() => {
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For bonus points this could also be simplified to process.nextTick(callback); if you want to change it while we're in here. Either way is fine though.

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Fixed

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@mscdex Strangely CI fails with your suggestion. Not sure why. Leaving it as is for the purposes of this PR.

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Ah, it's because we re-assign callback in the disposer.

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ronag commented Apr 30, 2020

Landed in d84f131

@ronag ronag closed this Apr 30, 2020
ronag added a commit that referenced this pull request Apr 30, 2020
finished would incorrectly believe that a Duplex is already
closed if either the readable or writable side has completed.

Fixes: #33130

PR-URL: #33133
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
targos pushed a commit that referenced this pull request May 4, 2020
finished would incorrectly believe that a Duplex is already
closed if either the readable or writable side has completed.

Fixes: #33130

PR-URL: #33133
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
@targos targos mentioned this pull request May 4, 2020
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Async iterator does not work with Duplex streams
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