1293205 - Warn about non-standard for-each regardless of JS version number

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Tooru Fujisawa [:arai]]

derived from bug 1083470.

now for-each is warning in parser depending on js version number

https://dxr.mozilla.org/mozilla-central/rev/763fe887c37cee5fcfe0f00e94fdffc84a41ea1c/js/src/frontend/Parser.cpp#6134
>             if (versionNumber() < JSVERSION_LATEST) {
>                 if (!report(ParseWarning, pc->sc->strict(), null(), JSMSG_DEPRECATED_FOR_EACH))
>                     return null();
>             }

we should warn regardless of the version number.
that will help add-on developers to migrate to standard syntax.

Comment 1

[Tooru Fujisawa [:arai]]

Attachment: Warn about non-standard for-each regardless of JS version number.

Removed versionNumber() check, and changed unused strict argument to false.
Also, made it warn-only-once, just like expression closure, to avoid flooding console.

Comment 2

[Florian Scholz (Open Web Docs)]

It would be useful to add [Learn more] to the warning and then explain what the standardized alternatives to for-each are.

To do that, a new page needs to be written here https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors and "JSMSG_DEPRECATED_FOR_EACH" and the URL needs to be added to https://dxr.mozilla.org/mozilla-central/source/devtools/server/actors/errordocs.js

Comment 3

[Tooru Fujisawa [:arai]]

Good idea :)

Added
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/For-each-in_loops_are_deprecated

will post errordocs.js patch shortly.

Comment 4

[Tooru Fujisawa [:arai]]

Attachment: Part 2: Link to MDN documentation from for-each warning.

Added link to For-each-in_loops_are_deprecated page.

Comment 5

[Florian Scholz (Open Web Docs)]

Comment on attachment 8787585 [details] [diff] [review]
Part 2: Link to MDN documentation from for-each warning.

Awesome, thank you!

Comment 6

[Tooru Fujisawa [:arai]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/4ab9576d4c6280d6f7dbbc75ea100d133ace1aad
Bug 1293205 - Part 1: Warn about non-standard for-each regardless of JS version number. r=evilpie

https://hg.mozilla.org/integration/mozilla-inbound/rev/3613d167d065e344e81fa6aab23492f71dd996d1
Bug 1293205 - Part 2: Link to MDN documentation from for-each warning. r=fscholz

Comment 7

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/4ab9576d4c62
https://hg.mozilla.org/mozilla-central/rev/3613d167d065

Comment 8

[Kohei Yoshino]

Added a note to the site compatibility doc: https://www.fxsitecompat.com/en-CA/docs/2015/for-each-in-loop-support-will-be-removed/

Comment 9

[Florian Scholz (Open Web Docs)]

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/For-each-in_loops_are_deprecated
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for_each...in
https://developer.mozilla.org/en-US/Firefox/Releases/51#JavaScript