1130798 - new RegExp().source should return "(?:)"

Status: RESOLVED FIXED

(Core :: JavaScript: Standard Library, defect)

Description

[Tooru Fujisawa [:arai]]

Derived from bug 1120169.

http://people.mozilla.org/~jorendorff/es6-draft.html#sec-get-regexp.prototype.source
> 7. Return EscapeRegExpPattern(src, flags).

http://people.mozilla.org/~jorendorff/es6-draft.html#sec-escaperegexppattern
> If P is the empty String, this specification can be met by letting S be "(?:)".

Currently `source` property returns empty string, and RegExpObject::toString does the replacement.

Comment 1

[Tooru Fujisawa [:arai]]

Attachment: Return "(?:)" for source of RegExp with empty pattern.

Green on try run: https://treeherder.mozilla.org/#/jobs?repo=try&revision=976d9db08519

Comment 2

[Till Schneidereit [:till]]

Comment on attachment 8560963 [details] [diff] [review]
Return "(?:)" for source of RegExp with empty pattern.

Review of attachment 8560963 [details] [diff] [review]:
-----------------------------------------------------------------

Nice, thanks.

Comment 3

[Till Schneidereit [:till]]

Release Note Request (optional, but appreciated)
[Why is this notable]: Potentially backwards-incompatible change
[Suggested wording]: RegExp.prototype.source now returns "(?:)" instead of the empty string for empty regular expressions
[Links (documentation, blog post, etc)]:
[1] https://mail.mozilla.org/pipermail/es-discuss/2012-March/021919.html (Search for RegExp)
[2] https://mail.mozilla.org/pipermail/es-discuss/2012-March/020815.html

Note that this is a potential backwards-compatibility issue as pointed out in [1]. It's been in Safari since 2011 though, so it'll most likely work.

Comment 4

[Tooru Fujisawa [:arai]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/7b89d8a612eb

Comment 5

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/7b89d8a612eb

Comment 6

[Florian Scholz (Open Web Docs)]

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/source
https://developer.mozilla.org/en-US/Firefox/Releases/38#JavaScript

Comment 7

[Lukas Blakk [:lsblakk] use ?needinfo]

Added to Aurora/DevEd releasenotes a:

Changed: RegExp.prototype.source now returns "(?:)" instead of the empty string for empty regular expressions

Comment 8

[Kohei Yoshino]

Added to the compat doc:
https://developer.mozilla.org/en-US/Firefox/Releases/38/Site_Compatibility