child_process: refactor internal/child_process.js #11366

notarseniy · 2017-02-14T03:50:40Z

Prefer === to == where possible
Remove condition that will always be false
Prefer for-loop statements to forEach where possible for perfomance reasons

Checklist

make -j4 test (UNIX), or vcbuild test (Windows) passes
commit message follows commit guidelines

Affected core subsystem(s)

child_process

mscdex · 2017-02-14T04:07:13Z

lib/internal/child_process.js

- stream.resume();
- });
+ if (subprocess.stdio === null || subprocess.stdio === undefined) return;
+ for (let i = 0; i < subprocess.stdio.length; i++) {


Use var instead of let here for better backportability (let used in this way is still slower at least in v6.x and v4.x).

This suggestion goes for all of the other occurrences below too.

OK! Is there a guide on code style?

@notarseniy make lint should have reported that issue. make lint is part of make test so if you ran tests, that should have come up as a lint error after the tests all passed. If the linter didn't report it, then there is probably a bug in our custom lint rule.

mscdex · 2017-02-14T04:07:51Z

lib/internal/child_process.js

- return;
- stream.resume();
- });
+ if (subprocess.stdio === null || subprocess.stdio === undefined) return;


I'm not sure this change is really worth it, the previous conditional is shorter and is equivalent in behavior.

Motivation of this change was this line with 'that-style' condition.

Well IMHO that other line could/should be changed to a non-strict equality check. The performance difference probably isn't measurable anymore.

mscdex · 2017-02-14T04:10:26Z

lib/internal/child_process.js

- });
+ if (subprocess.stdio === null || subprocess.stdio === undefined) return;
+ for (let i = 0; i < subprocess.stdio.length; i++) {
+ if (!subprocess.stdio[i] || !subprocess.stdio[i].readable || subprocess.stdio[i]._readableState.readableListening) 


Instead of looking up the value each time, add a temporary variable before the conditional. For example:

const stdio = subprocess.stdio; for (var i = 0; i < stdio.length; ++i) { const stream = stdio[i]; // .... keep rest of the code the same }

This suggestion goes for all of the other occurrences below too.

Yeah, sounds good. Will fix this

Good comment. Will fix.

mscdex · 2017-02-14T04:12:21Z

lib/internal/child_process.js

@@ -800,7 +800,7 @@ function _validateStdio(stdio, sync) {
 stdio = i < 3 ? 'pipe' : 'ignore';
 }

- if (stdio === null || stdio === 'ignore') {
+ if (stdio === 'ignore') {


Why this change? This would change behavior...

In previous condition we're handling stdio === null, so this condition never will be executed with stdio === null

notarseniy · 2017-02-14T05:12:25Z

Commited with fixes of comments.

Trott · 2017-02-14T06:20:54Z

CI: https://ci.nodejs.org/job/node-test-pull-request/6398/

mscdex · 2017-02-14T07:39:04Z

More linting issues it seems. Run make jslint locally to find the specifics.

I'm guessing it's due to the duplicate var i; declarations in the two new for-loops.

mscdex · 2017-02-14T07:40:18Z

lib/internal/child_process.js

- return;
+ if (subprocess.stdio === null || subprocess.stdio === undefined) return;
+
+ const stdio = subprocess.stdio;


This could probably be moved to the top of the function, where the first conditional can take advantage of it.

* Prefer === to == where possible * Remove condition that will always be false * Prefer for-loop statements to forEach where possible for perfomance reasons

notarseniy · 2017-02-14T12:44:02Z

Recommited with fixes. /cc @Trott @mscdex

mscdex · 2017-02-14T16:34:23Z

CI: https://ci.nodejs.org/job/node-test-pull-request/6405/

mscdex · 2017-02-14T17:12:04Z

CI is green. LGTM.

notarseniy · 2017-02-18T18:52:24Z

Bump! 😅 What the status of PR? Any other comments or additions?

* Prefer === to == where possible * Remove condition that will always be false * Prefer for-loop statements to forEach where possible for perfomance reasons PR-URL: #11366 Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Sam Roberts <vieuxtech@gmail.com> Reviewed-By: Michaël Zasso <targos@protonmail.com> Reviewed-By: Brian White <mscdex@mscdex.net>

targos · 2017-02-18T19:03:22Z

@notarseniy I think it has just been forgotten. I went ahead and landed it in 8fc362e. Thanks for the contribution!

notarseniy · 2017-02-18T19:04:05Z

Thats okay :) Thank you too!

* Prefer === to == where possible * Remove condition that will always be false * Prefer for-loop statements to forEach where possible for perfomance reasons PR-URL: #11366 Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Sam Roberts <vieuxtech@gmail.com> Reviewed-By: Michaël Zasso <targos@protonmail.com> Reviewed-By: Brian White <mscdex@mscdex.net>

nodejs-github-bot added the child_process Issues and PRs related to the child_process subsystem. label Feb 14, 2017

mscdex reviewed Feb 14, 2017

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notarseniy force-pushed the internal-child-process-fix branch from 03eba26 to 0b3efdc Compare February 14, 2017 05:00

mscdex reviewed Feb 14, 2017

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notarseniy force-pushed the internal-child-process-fix branch from 0b3efdc to 9bfcaf4 Compare February 14, 2017 12:34

child_process: refactor internal/child_process.js

efaa7d7

* Prefer === to == where possible * Remove condition that will always be false * Prefer for-loop statements to forEach where possible for perfomance reasons

notarseniy force-pushed the internal-child-process-fix branch from 9bfcaf4 to efaa7d7 Compare February 14, 2017 12:36

cjihrig approved these changes Feb 14, 2017

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sam-github approved these changes Feb 15, 2017

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targos approved these changes Feb 18, 2017

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targos closed this Feb 18, 2017

notarseniy deleted the internal-child-process-fix branch February 18, 2017 19:04

italoacasas mentioned this pull request Feb 25, 2017

7.7.0 Proposal #11553

Merged

MylesBorins mentioned this pull request Mar 9, 2017

v6.10.1 proposal #11759

Merged

MylesBorins mentioned this pull request Mar 9, 2017

v4.8.1 proposal #11760

Merged

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child_process: refactor internal/child_process.js #11366

child_process: refactor internal/child_process.js #11366

notarseniy commented Feb 14, 2017 •

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child_process: refactor internal/child_process.js #11366

child_process: refactor internal/child_process.js #11366

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