1222552 - Remove String generics

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Tooru Fujisawa [:arai]]

String generics are non-standard SpiderMonkey extension and they should be removed.
  * String.charAt
  * String.charCodeAt
  * String.concat
  * String.contains
  * String.endsWith
  * String.includes
  * String.indexOf
  * String.lastIndexOf
  * String.localeCompare
  * String.match
  * String.normalize
  * String.replace
  * String.search
  * String.slice
  * String.split
  * String.startsWith
  * String.substr
  * String.substring
  * String.toLocaleLowerCase
  * String.toLocaleUpperCase
  * String.toLowerCase
  * String.toUpperCase
  * String.trim
  * String.trimLeft
  * String.trimRight

Comment 1

[Kohei Yoshino [:kohei]]

Posted the site compatibility doc: https://www.fxsitecompat.com/en-US/docs/2015/array-string-generics-will-be-removed/

Comment 2

[Tom S [:evilpie]]

I think it's time we seriously investigate this and bug 1222547. The String variant is probably less used, but we definitely need to add some telemetry. The static String functions already have warnings, but the Array methods don't. This also means those are still used in Firefox code.

Comment 3

[Tom S [:evilpie]]

The telemetry for this produced quite interesting results.

method	usage
toLowerCase	519106 (97.75%)
concat	4898 (0.92%)
slice	3490 (0.66%)
trim	3336 (0.63%)

The rest is basically at 0%. source

I wonder if we should just go ahead and remove all of the rest? Except for toLowerCase even the rest feels quite low.

Comment 4

[André Bargull [:anba]]

There's an old Mootools version in-tree, which, as part of its initialisation, seems to call String.toLowerCase. Maybe this Mootools version is still used on the Web and that's why toLowerCase is so prominent in the telemetry data? In that case it's safe to remove toLowerCase, because Mootools will add it back.

Comment 5

[Tom S [:evilpie]]

(In reply to André Bargull [:anba] from comment #4)

There's an old Mootools version in-tree, which, as part of its initialisation, seems to call String.toLowerCase. Maybe this Mootools version is still used on the Web and that's why toLowerCase is so prominent in the telemetry data? In that case it's safe to remove toLowerCase, because Mootools will add it back.

Wow good find! I really hope this is true and we can just remove everything.

Comment 6

[Tom S [:evilpie]]

Attachment: Bug 1222552 - Remove String generics. r?jorendorff!

Comment 7

[Jason Orendorff [:jorendorff]]

That really is an amazing find, anba. Wow.

Comment 8

[Tom S [:evilpie]]

Attachment: Bug 1222552 - Fix xpconnect test. r?smaug

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/c59acf298136
Remove String generics. r=jorendorff
https://hg.mozilla.org/integration/autoland/rev/a8c448b92913
Fix xpconnect test. r=smaug

Comment 10

[Stefan Hindli [:stefan_hindli]]

https://hg.mozilla.org/mozilla-central/rev/c59acf298136
https://hg.mozilla.org/mozilla-central/rev/a8c448b92913

Comment 11

[Florin Strugariu [:Bebe]]

== Change summary for alert #20084 (as of Sat, 23 Mar 2019 05:37:40 GMT) ==

Improvements:

1% Base Content JS linux64 pgo stylo 3,999,578.67 -> 3,968,909.33
1% Base Content JS linux64-pgo-qr opt stylo 3,999,470.67 -> 3,968,886.67
1% Base Content JS windows10-64-pgo-qr opt stylo 4,073,260.00 -> 4,046,252.00
1% Base Content JS windows10-64 pgo stylo 4,073,281.33 -> 4,046,340.00
1% Base Content JS osx-10-10 opt stylo 4,000,505.33 -> 3,974,025.33
0% Base Content JS windows7-32 pgo stylo 3,165,454.67 -> 3,150,896.00

For up to date results, see: https://treeherder.mozilla.org/perf.html#/alerts?id=20084

Comment 12

[Kohei Yoshino [:kohei]]

Posted site compatibility note: https://www.fxsitecompat.com/en-CA/docs/2019/non-standard-string-generics-have-been-removed/

Comment 13

[Florian Scholz (Open Web Docs)]

Sorry this slipped through somehow in time for Firefox 68.

Announced on Firefox 68 release notes: https://developer.mozilla.org/en-US/docs/Mozilla/Firefox/Releases/68#JavaScript

Updated the warning page that is shown in earlier Firefox versions: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/Deprecated_String_generics

Removed the entire "String generics" section from the String API docs: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String