Unexpected error highlighting with YARA grammar on linguist

[wesinator]

Preliminary Steps

Please confirm you have...

• [x] reviewed How Linguist Works,
• [x] reviewed the Troubleshooting docs,
• [x] considered implementing an override,
• [x] verified an issue has not already been logged for your issue (linguist issues).

Problem Description

YARA language highlighting on Github unexpectedly highlights certain sequences (\x) in red as if it interprets as an error. Not reproducible with the same grammar version in atom:

URL of the affected repository: https://github.com/viper-framework/yara-rules/blob/6a8a376542320c0c58ba15cd027653c76e05af4e/leverage.yar#L15

"\x00"

Expected: \x is not red

[lildude]

This is going to be due to the grammar using a quantifier regexp that is not valid PCRE (as used by GitHub) and but is a valid Oniguruma Regular Expression (as used by Atom).

The incompatibility is in the use of {,2} (and similar usage elsewhere) in the grammar in the regex at https://github.com/blacktop/language-yara/blob/1093d3d528dce6b3c8362dfedfce978cf9979b1e/grammars/yara.cson#L78, specifically {,2} isn't valid PCRE (see quantifiers at https://perldoc.perl.org/perlreref.html#QUANTIFIERS) and needs to be {0,2}. Oniguruma however allows this usage hence it works in Atom.

So as with almost all highlighting issues, this is a problem with the grammar. Please log an issue with the grammar.

Closing as this is not a problem with Linguist.

[pchaigno]

I've sent a pull request (cf. blacktop/language-yara#4) to fix it.