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Re: [selectors] How to handle unexpected hyphens in the language range of :lang()?

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Tue, 11 Nov 2014 16:14:01 -0800
Message-ID: <CAAWBYDAopXzf-iqsL-Ghs_8_ckzW0Dva4jxwPO486OTM3_4Adw@mail.gmail.com>
To: Benjamin Poulain <bpoulain@apple.com>
Cc: www-style list <www-style@w3.org>
On Mon, Nov 10, 2014 at 9:17 PM, Benjamin Poulain <bpoulain@apple.com> wrote:
> Hi,
>
> I am not sure what is the correct way to handle “invalid" language ranges
> with :lang().
>
> The draft says that :lang() accepts valid CSS identifiers
> (http://dev.w3.org/csswg/selectors4/#the-lang-pseudo).
>
> RFC4647 is significantly more restrictive.
>
> Given the following values:
>     en-
>     en--us
> It is no clear how to handle the step 3.3.2 of RFC4647.
>
> We could either ignore empty groups:
>     en- -> [“en”, “”] -> [“en”]
>     en--us -> [“en”, “”, “us”] -> [“en”, “us”]
>
> Or consider them part of the matching, in which case they always fail to
> match since the normalized element’s language would never contains the empty
> group.
>
> Is this defined anywhere by any chance?
> I assume they should always fail for compatibility with Level 3.

Tags like that are definitely valid at the CSS level; they don't
trigger error-handling.

Parsing and matching of language tags is defined by RFC4647; do
whatever the RFC says to do for malformed language tags.

If we assume that "en-" and "en--us" are valid (dunno if we should,
I'm just doing a cursory skim of the RFC), then following 3.3.2's algo
seems straightforward: you'll get empty groups, which won't match
anything.

~TJ
Received on Wednesday, 12 November 2014 00:14:48 UTC

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