Re: Backwards compatibility and U+2E2F in `Identifier`s
On Mon, Aug 19, 2013 at 5:25 AM, Mathias Bynens math...@qiwi.be wrote: After comparing the output, I noticed that both regular expressions are identical except for the following: ECMAScript 5 allows U+2E2F VERTICAL TILDE in `IdentifierStart` and `IdentifierPart`, but ECMAScript 6 / Unicode TR31 doesn’t. Per ES6 identifiers start with code points whose category is ID_Start which per http://www.unicode.org/reports/tr31/ includes Lm which per http://www.unicode.org/Public/UNIDATA/UnicodeData.txt is true for U+2E2F. So why exactly is it disallowed? Unless I'm missing something, the discussion we had in TC39 yesterday was moot, and these bugs are invalid: https://bugs.ecmascript.org/show_bug.cgi?id=1802 https://bugzilla.mozilla.org/show_bug.cgi?id=917436 https://bugs.webkit.org/show_bug.cgi?id=121541 https://code.google.com/p/v8/issues/detail?id=2892 And IE10 and maybe IE11 have a bug in not allowing it. -- http://annevankesteren.nl/ ___ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
Re: Backwards compatibility and U+2E2F in `Identifier`s
On 18 Sep 2013, at 21:05, Anne van Kesteren ann...@annevk.nl wrote: On Mon, Aug 19, 2013 at 5:25 AM, Mathias Bynens math...@qiwi.be wrote: After comparing the output, I noticed that both regular expressions are identical except for the following: ECMAScript 5 allows U+2E2F VERTICAL TILDE in `IdentifierStart` and `IdentifierPart`, but ECMAScript 6 / Unicode TR31 doesn’t. Per ES6 identifiers start with code points whose category is ID_Start which per http://www.unicode.org/reports/tr31/ includes Lm which per http://www.unicode.org/Public/UNIDATA/UnicodeData.txt is true for U+2E2F. So why exactly is it disallowed? `ID_Start` includes code points in the `Lm` category indeed, but then later explicitly disallows `Pattern_Syntax` and `Pattern_White_Space` code points. As it says on the page you linked to: In set notation, this is [[:L:][:Nl:]--[:Pattern_Syntax:]--[:Pattern_White_Space:]] plus stability extensions. U+2E2F has the `Pattern_Syntax` property and is thus not a valid `ID_Start` code point. ___ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
Re: Backwards compatibility and U+2E2F in `Identifier`s
I had no intentions specific to U+2E2F when I proposed relying on UTR 31 - the change is simply the effect of the character properties that the Unicode Technical Committee assigned to this character. I don't think there's a real problem. U+2E2F was added in Unicode version 5.1. ECMAScript 5.1 requires only support for Unicode 3.0, and warns If portability is a concern, programmers should only employ identifier characters defined in Unicode 3.0 (section 7.6). IE 10 throws a SyntaxError if the character is used in an identifier. BTW, if that's the only difference between the regular expressions for ES 5.1 and ES 6, then at least one of them is wrong - ES 6 allows supplementary characters in identifiers, while ES 5.1 doesn't. Norbert On Aug 19, 2013, at 2:25 , Mathias Bynens math...@qiwi.be wrote: I wrote a (new) script that generates a regular expression that matches valid JavaScript identifiers as per ECMAScript 5.1 / Unicode v6.2.0. http://mathiasbynens.be/demo/javascript-identifier-regex Then, I made it do the same thing according to the latest ECMAScript 6 draft, which refers to Unicode Standard Annex #31: Unicode Identifier and Pattern Syntax (http://www.unicode.org/reports/tr31/). After comparing the output, I noticed that both regular expressions are identical except for the following: ECMAScript 5 allows U+2E2F VERTICAL TILDE in `IdentifierStart` and `IdentifierPart`, but ECMAScript 6 / Unicode TR31 doesn’t. Was this potentially breaking change intentional? I’m fine with disallowing U+2E2F, but only if we’re sure it doesn’t break any existing code. Mathias http://mathiasbynens.be/ ___ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss ___ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
Re: Backwards compatibility and U+2E2F in `Identifier`s
I had no intentions specific to U+2E2F when I proposed relying on UTR 31 - the change is simply the effect of the character properties that the Unicode Technical Committee assigned to this character. I don't think there's a real problem. U+2E2F was added in Unicode version 5.1. ECMAScript 5.1 requires only support for Unicode 3.0, and warns If portability is a concern, programmers should only employ identifier characters defined in Unicode 3.0 (section 7.6). IE 10 throws a SyntaxError if the character is used in an identifier. BTW, if that's the only difference between the regular expressions for ES 5.1 and ES 6, then at least one of them is wrong - ES 6 allows supplementary characters in identifiers, while ES 5.1 doesn't. It’s the only difference in the BMP range. (Like you said, differences in the astral range are to be expected, since astral symbols weren’t allowed in ES5. No back-compat issues there.) ___ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
Re: Backwards compatibility and U+2E2F in `Identifier`s
Thanks for filing. I don't recall any reason for this and it seems bad to break compatibility. It may be that Norbert and Allen just missed your post on Monday; cc'ing them. /be Mathias Bynens wrote: On 19 Aug 2013, at 11:25, Mathias Bynensmath...@qiwi.be wrote: After comparing the output, I noticed that both regular expressions are identical except for the following: ECMAScript 5 allows U+2E2F VERTICAL TILDE in `IdentifierStart` and `IdentifierPart`, but ECMAScript 6 / Unicode TR31 doesn’t. Was this potentially breaking change intentional? I’m fine with disallowing U+2E2F, but only if we’re sure it doesn’t break any existing code. Follow-up: since this thread is being ignored, I filedhttps://bugs.ecmascript.org/show_bug.cgi?id=1802. ___ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss ___ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
