Outstanding Grammar Issues

[vmg]

The following is a detailed list of all the outstanding issues in the grammars that GitHub.com uses for syntax highlighting the code in our website.

These issues are detected by our grammars compiler (#3915) and are probably causing minor rendering bugs in the website.

Help is very much welcome! If you're seeing bugs or rendering issues in your source code in GitHub, please start by taking a look at this list to make sure we're not detecting any issues in your language's grammar.

Feel free to ask any questions about any given issue and what would be the appropriate way to fix it. I'll keep the issue up-to-date as I work through grammar fixes myself.

cc @github/linguist @pchaigno @Alhadis

---

Last updated: 17 Mar 2026

• repository vendor/grammars/MATLAB-Language-grammar (from https://github.com/mathworks/MATLAB-Language-grammar) (16 errors)

  • Invalid regex in grammar: source.matlab (in Matlab.tmbundle/Syntaxes/MATLAB.tmLanguage) contains a malformed regex (regex "(\)|(?<!\.{3}.*)\n)": lookbehind assertion is not fixed length (at offset 15))
  • Invalid regex in grammar: source.matlab (in Matlab.tmbundle/Syntaxes/MATLAB.tmLanguage) contains a malformed regex (regex "(?<!\.{3}.*)(?:(?=([,;])(?![^(]*...": lookbehind assertion is not fixed length (at offset 11))
  • Invalid regex in grammar: source.matlab (in Matlab.tmbundle/Syntaxes/MATLAB.tmLanguage) contains a malformed regex (regex "(?<!\.{3}.*)(?:(?=[,;](?![^(]*\)...": lookbehind assertion is not fixed length (at offset 11))
  • Invalid regex in grammar: source.matlab (in Matlab.tmbundle/Syntaxes/MATLAB.tmLanguage) contains a malformed regex (regex "(?<!\.{3}.*)(?:(?=([,;])(?![^(]*...": lookbehind assertion is not fixed length (at offset 11))
  • Invalid regex in grammar: source.matlab (in Matlab.tmbundle/Syntaxes/MATLAB.tmLanguage) contains a malformed regex (regex "(?<!\.{3}.*)(?:(?=([,;])(?![^(]*...": lookbehind assertion is not fixed length (at offset 11))
  • Invalid regex in grammar: source.matlab (in Matlab.tmbundle/Syntaxes/MATLAB.tmLanguage) contains a malformed regex (regex "(?<!\.{3}.*)(?:(?=([,;])(?![^(]*...": lookbehind assertion is not fixed length (at offset 11))
  • Invalid regex in grammar: source.matlab (in Matlab.tmbundle/Syntaxes/MATLAB.tmLanguage) contains a malformed regex (regex "(?<!\.{3}.*)(?:(?=[,;](?![^(]*\)...": lookbehind assertion is not fixed length (at offset 11))
  • Invalid regex in grammar: source.matlab (in Matlab.tmbundle/Syntaxes/MATLAB.tmLanguage) contains a malformed regex (regex "(?<!\.{3}.*)(?:(?=([,;])(?![^(]*...": lookbehind assertion is not fixed length (at offset 11))
  • Invalid regex in grammar: source.matlab (in Matlab.tmbundle/Syntaxes/MATLAB.tmLanguage) contains a malformed regex (regex "(?<!\.{3}.*)(?:(?=[,;](?![^(]*\)...": lookbehind assertion is not fixed length (at offset 11))
  • Invalid regex in grammar: source.matlab (in Matlab.tmbundle/Syntaxes/MATLAB.tmLanguage) contains a malformed regex (regex "(?=;|,|(?<!(?:\.{3}.*))\n|%)": lookbehind assertion is not fixed length (at offset 22))
  • Invalid regex in grammar: source.matlab (in Matlab.tmbundle/Syntaxes/MATLAB.tmLanguage) contains a malformed regex (regex "(\))?[^\S\n]*(?=;|,|(?<!(?:\.{3}...": lookbehind assertion is not fixed length (at offset 35))
  • Invalid regex in grammar: source.matlab (in Matlab.tmbundle/Syntaxes/MATLAB.tmLanguage) contains a malformed regex (regex "(?<=\))|(?>(?<!\.{3}.*)\n)": lookbehind assertion is not fixed length (at offset 22))
  • Invalid regex in grammar: source.matlab (in Matlab.tmbundle/Syntaxes/MATLAB.tmLanguage) contains a malformed regex (regex "(\)|(?<!\.{3}.*)\n)": lookbehind assertion is not fixed length (at offset 15))
  • Invalid regex in grammar: source.matlab (in Matlab.tmbundle/Syntaxes/MATLAB.tmLanguage) contains a malformed regex (regex "(\}|(?<!\.{3}.*)\n)": lookbehind assertion is not fixed length (at offset 15))
  • Invalid regex in grammar: source.matlab (in Matlab.tmbundle/Syntaxes/MATLAB.tmLanguage) contains a malformed regex (regex "(\)|(?<!\.{3}.*)\n)": lookbehind assertion is not fixed length (at offset 15))
  • Invalid regex in grammar: source.matlab (in Matlab.tmbundle/Syntaxes/MATLAB.tmLanguage) contains a malformed regex (regex "(\)|(?<!\.{3}.*)\n)": lookbehind assertion is not fixed length (at offset 15))

• repository vendor/grammars/Sublime-SQF-Language (from https://github.com/JonBons/Sublime-SQF-Language) (1 errors)

  • Invalid regex in grammar: source.sqf (in SQF.tmLanguage) contains a malformed regex (regex "\b(?i:action|actionids|actionkey...": definition too long (38105 bytes))

• repository vendor/grammars/TypeScript-TmLanguage (from https://github.com/Microsoft/TypeScript-TmLanguage) (2 errors)

  • Invalid regex in grammar: source.ts (in TypeScript.tmLanguage) contains a malformed regex (regex "(?!(?<![_$[:alnum:]])(?:(?<=\.\....": lookbehind assertion is not fixed length (at offset 731))
  • Invalid regex in grammar: source.tsx (in TypeScriptReact.tmLanguage) contains a malformed regex (regex "(?!(?<![_$[:alnum:]])(?:(?<=\.\....": lookbehind assertion is not fixed length (at offset 731))

• repository vendor/grammars/apex-tmLanguage (from https://github.com/forcedotcom/apex-tmLanguage.git) (2 errors)

  • Invalid regex in grammar: source.apex (in grammars/apex.tmLanguage) contains a malformed regex (regex "(?=\s(?!\())|(?=\s*$)|(?<=\s*\))": lookbehind assertion is not fixed length (at offset 31))
  • Invalid regex in grammar: source.soql (in grammars/soql.tmLanguage) contains a malformed regex (regex "(?=\s(?!\())|(?=\s*$)|(?<=\s*\))": lookbehind assertion is not fixed length (at offset 31))

• repository vendor/grammars/atom-language-julia (from https://github.com/JuliaEditorSupport/atom-language-julia) (1 errors)

  • Invalid regex in grammar: source.julia (in grammars/julia.cson) contains a malformed regex (regex "(?<=\S\s+)\b(as)\b(?=\s+\S)": lookbehind assertion is not fixed length (at offset 9))

• repository vendor/grammars/atom-language-purescript (from https://github.com/purescript-contrib/atom-language-purescript) (1 errors)

  • Invalid regex in grammar: source.purescript (in grammars/purescript.cson) contains a malformed regex (regex "(?<=(\||=)\s*)([\p{Lu}\p{Lt}][\p...": lookbehind assertion is not fixed length (at offset 13))

• repository vendor/grammars/csharp-tmLanguage (from https://github.com/dotnet/csharp-tmLanguage) (4 errors)

  • Invalid regex in grammar: source.cs (in grammars/csharp.tmLanguage) contains a malformed regex (regex "(?<!\.\s*)\b(await)\b": lookbehind assertion is not fixed length (at offset 9))
  • Invalid regex in grammar: source.cs (in grammars/csharp.tmLanguage) contains a malformed regex (regex "(?<!\.\s*)\b(await)\b": lookbehind assertion is not fixed length (at offset 9))
  • Invalid regex in grammar: source.cs (in grammars/csharp.tmLanguage) contains a malformed regex (regex "\G(?=(?~\*/)$)": unrecognized character after (? or (?- (at offset 7))
  • Invalid regex in grammar: source.cs (in grammars/csharp.tmLanguage) contains a malformed regex (regex "^(\s*+)(\*(?!/))?(?=(?~\*/)$)": unrecognized character after (? or (?- (at offset 22))

• repository vendor/grammars/gap-tmbundle (from https://github.com/dhowden/gap-tmbundle) (3 errors)

  • Invalid regex in grammar: source.gap (in Syntaxes/GAP.tmLanguage) contains a malformed regex (regex "\b(16Bits_AssocWord|16Bits_Depth...": definition too long (65523 bytes))
  • Invalid regex in grammar: source.gap (in Syntaxes/GAP.tmLanguage) contains a malformed regex (regex "\b(IndicesChiefNormalSteps|Indic...": definition too long (65529 bytes))
  • Invalid regex in grammar: source.gap (in Syntaxes/GAP.tmLanguage) contains a malformed regex (regex "\b(SMTX_GoodElementGModule|SMTX_...": definition too long (42470 bytes))

• repository vendor/grammars/godot-vscode-plugin (from https://github.com/godotengine/godot-vscode-plugin) (1 errors)

  • Invalid regex in grammar: source.gdscript (in syntaxes/GDScript.tmLanguage.json) contains a malformed regex (regex "(?<!/\s*)(\$\s*|%|\$%\s*)(/\s*)?...": lookbehind assertion is not fixed length (at offset 8))

• repository vendor/grammars/linter-lilypond (from https://github.com/nwhetsell/linter-lilypond) (1 errors)

  • Invalid regex in grammar: source.lilypond (in grammars/lilypond.cson) contains a malformed regex (regex "(?<!-)\b(!=|\*(?:(?:location|par...": definition too long (35491 bytes))

• repository vendor/grammars/mathematica-tmbundle (from https://github.com/shadanan/mathematica-tmbundle) (1 errors)

  • Invalid regex in grammar: source.mathematica (in Syntaxes/Mathematica.tmLanguage) contains a malformed regex (regex "(\b|(?<=_))(Abort|AbortKernels|A...": definition too long (54020 bytes))

• repository vendor/grammars/nu-grammar (from https://github.com/hustcer/nu-grammar.git) (1 errors)

  • Invalid regex in grammar: source.nushell (in grammars/tmLanguage.json) contains a malformed regex (regex "(?<=]\s*)(:)\s+(\[)": lookbehind assertion is not fixed length (at offset 8))

• repository vendor/grammars/objective-c.tmbundle (from https://github.com/textmate/objective-c.tmbundle) (2 errors)

  • Invalid regex in grammar: source.objc.platform (in Syntaxes/Platform.tmLanguage) contains a malformed regex (regex "\b(?:AB(?:AddRecordsError|Multip...": definition too long (32854 bytes))
  • Invalid regex in grammar: source.objc.platform (in Syntaxes/Platform.tmLanguage) contains a malformed regex (regex "\b(?:A(?:M(?:Action(?:A(?:pplica...": definition too long (44404 bytes))

• repository vendor/grammars/qsharp (from https://github.com/microsoft/qsharp.git) (2 errors)

  • Invalid regex in grammar: source.openqasm (in source/vscode/syntaxes/openqasm.tmLanguage.json) contains a malformed regex (regex "(?<!\s*\.\s*)\b(in|for|return|if...": lookbehind assertion is not fixed length (at offset 12))
  • Invalid regex in grammar: source.openqasm (in source/vscode/syntaxes/openqasm.tmLanguage.json) contains a malformed regex (regex "(?<!\s*\.\s*)\b(OPENQASM|include...": lookbehind assertion is not fixed length (at offset 12))

• repository vendor/grammars/sprocket-vscode (from https://github.com/stjude-rust-labs/sprocket-vscode.git) (1 errors)

  • Invalid regex in grammar: source.wdl (in syntaxes/wdl.tmGrammar.json) contains a malformed regex (regex "`(?<=^\s*|;\s*|&\s*||\s*|(\s*|``...": lookbehind assertion is not fixed length (at offset 8))

• repository vendor/grammars/sublime-autoit (from https://github.com/AutoIt/SublimeAutoItScript) (2 errors)

  • Invalid regex in grammar: source.autoit (in AutoIt.tmLanguage) contains a malformed regex (regex "\b(?i:_array1dtohistogram|_array...": definition too long (39591 bytes))
  • Invalid regex in grammar: source.autoit (in AutoIt.tmLanguage) contains a malformed regex (regex "\b(?i:_guictrltoolbar_getbuttoni...": definition too long (39600 bytes))

• repository vendor/grammars/turtle.tmbundle (from https://github.com/peta/turtle.tmbundle) (5 errors)

  • Invalid regex in grammar: source.turtle (in Syntaxes/Turtle.tmLanguage) contains a malformed regex (regex "(?x) (?<PN_CHARS_U>[\p{L}\p{M...": PCRE does not support \L, \l, \N{name}, \U, or \u (at offset 73))
  • Invalid regex in grammar: source.turtle (in Syntaxes/Turtle.tmLanguage) contains a malformed regex (regex "(?x)( (?: [\p{L}\p{M}] | [:0...": PCRE does not support \L, \l, \N{name}, \U, or \u (at offset 121))
  • Invalid regex in grammar: source.turtle (in Syntaxes/Turtle.tmLanguage) contains a malformed regex (regex "(?x) (?<PNAME_NS> (?: (?: [\...": PCRE does not support \L, \l, \N{name}, \U, or \u (at offset 68))
  • Invalid regex in grammar: source.turtle (in Syntaxes/Turtle.tmLanguage) contains a malformed regex (regex "\[[\u20\u9\uD\uA]*\]": PCRE does not support \L, \l, \N{name}, \U, or \u (at offset 4))
  • Invalid regex in grammar: source.turtle (in Syntaxes/Turtle.tmLanguage) contains a malformed regex (regex "(?x)((?<=\s|^|_)(?:[\p{L}\p{M}] ...": PCRE does not support \L, \l, \N{name}, \U, or \u (at offset 57))

• repository vendor/grammars/vscode-bitbake (from https://github.com/yoctoproject/vscode-bitbake.git) (1 errors)

  • Invalid regex in grammar: source.bb (in client/syntaxes/bitbake.tmLanguage.json) contains a malformed regex (regex "(?<=^|^fakeroot +)\b(python|def)...": lookbehind assertion is not fixed length (at offset 17))

• repository vendor/grammars/vscode-just (from https://github.com/nefrob/vscode-just.git) (6 errors)

  • Invalid regex in grammar: source.just (in syntaxes/just.tmLanguage.json) contains a malformed regex (regex "(?<=^[^\s]+)": lookbehind assertion is not fixed length (at offset 11))
  • Invalid regex in grammar: source.just (in syntaxes/just.tmLanguage.json) contains a malformed regex (regex "(?<=^[^\s]+)": lookbehind assertion is not fixed length (at offset 11))
  • Invalid regex in grammar: source.just (in syntaxes/just.tmLanguage.json) contains a malformed regex (regex "(?<=^[^\s]+)": lookbehind assertion is not fixed length (at offset 11))
  • Invalid regex in grammar: source.just (in syntaxes/just.tmLanguage.json) contains a malformed regex (regex "(?<=^[^\s]+)": lookbehind assertion is not fixed length (at offset 11))
  • Invalid regex in grammar: source.just (in syntaxes/just.tmLanguage.json) contains a malformed regex (regex "(?<=^[^\s]+)": lookbehind assertion is not fixed length (at offset 11))
  • Invalid regex in grammar: source.just (in syntaxes/just.tmLanguage.json) contains a malformed regex (regex "(?<=^[^\s]+)": lookbehind assertion is not fixed length (at offset 11))

• repository vendor/grammars/vscode-yara (from https://github.com/infosec-intern/vscode-yara.git) (1 errors)

  • Invalid regex in grammar: source.yara (in yara/syntaxes/yara.tmLanguage.json) contains a malformed regex (regex "(?<=(^|[\)]|\b(?:them)\b))(?:\s*...": lookbehind assertion is not fixed length (at offset 25))

---

Other

The following grammars are not being updated due to problems with the grammars:

• vendor/grammars/Sublime-QML - skozlovf/Sublime-QML - the project has been restructured and rewritten and only provides a Sublime 3 compatible grammar which is not supported.
• vendor/grammars/cds-textmate-grammar recently introduced changes that resulted in over 20 unknown property name after \P or \p errors so we've not updated that grammar.
• vendor/grammars/VscodeAdblockSyntax fails to compile so won't be updated until resolved.
• vendor/grammars/zenstack - restructured and now doesn't contain a complete grammar file.

[lildude]

Thanks for the useful and actionable list @vmg. One question...

repository vendor/grammars/language-babel (from https://github.com/gandm/language-babel) (14 errors)

Is this the actual upstream grammar as it stands now or the old pinned copy we're shipping with Linguist at the moment?

I'm assuming the latter, but thought I'd check to be sure.

[vmg]

I'm assuming the latter, but thought I'd check to be sure.

Correct! I fucked up my submodules. Sorry about that, I'll update the list with the proper URL.

[Alhadis]

Hey, sorry about the (really) slow response. My MacBook died last week, which means I've been painfully limited in what I'm able to do on GitHub (I'm using my work's computer for the time being, when time permits).

The issues reported by my grammars are easily fixed; but the LilyPond grammar should be fixed with a PR to the upstream repository. Basically, the scope.AtLilyPond should be replaced with just scope.lilypond so it's consistent with other LilyPond grammars (and I can therefore replace the offending rule in text.roff with a single inclusion: {include: "source.lilypond"}.

[Alhadis]

What's the maximum token length permitted by the new compiler? I was about to start fixing the issues with Emacs Lisp's grammar, but realised I don't have the actual limit to go by.

Admittedly, I'm not really fond about the size limit, because the "fix" here is to simply break the pattern down into multiple rules that're bunched together under the same name. It feels terribly hacky, and the fact that the rules in question were compiled from an external source means that updating the list in future might be made more complicated...

[vmg]

@Alhadis: Sorry, you caught me on Holidays. The maximum size is enforced by PCRE, not by our parser, and it's 64kb for a single regexp. I'm aware it's a bummer, but it's the way PCRE was designed.

[Alhadis]

That's understandable. How is whitespace treated inside expressions which use "expanded" notation...?

m/
	abc
	(?:
		xyz
	)
	(?=\w+)
/x;

Because there are two different ways to represent that in CSON. One is with an ordinary quoted-string, which includes embedded newlines as part of the pattern...

pattern: "(?x)
	abc
	(?:
		xyz
	)
	(?=\\w+)
"

... and the other is to use triple-quoted strings ("heredocs"):

pattern: """(?x)
	abc
	(?:
		xyz
	)
	(?=\\w+)
"""

The latter will strip as much indentation as it can, leaving some (but not all) horizontal whitespace after the CSON-to-JSON conversion:

(?x)
	abc
	(?:
	        xyz
	)
	(?=\\w+)

Now this won't make any difference to the regex engine, but it will to my subdivision efforts... 😀

[vmg]

@Alhadis I'm honestly not sure of how exactly does PCRE implement this -- you should be able to test it out by simply downloading libpcre and trying to compile in the regexps. Our parser has no custom behavior here.