Lint what matters
Find duplicate tokens, undefined symbols, unreachable rules, circular references, and style drift with focused, configurable checks.
collie lint grammars/
Built for Lrama-style BNF
Catch grammar mistakes before your parser does.
Collie lints and formats .y files, catching undefined symbols, recursion trouble, ambiguous precedence, and the quiet mistakes hiding between productions.
gem install collie
1 %token NUMBER PLUS
2 %%
3
4 expr:
5 NUMBER
6 | expr PLUS term
7 ;errorUndefinedSymbol6:15
Symbol term is not defined as a token or rule.
warningAmbiguousPrecedence6:10
Operator PLUS has no precedence declaration.
20built-in rules
5configuration profiles
4report formats
3.2+Ruby support
One tool for the grammar before the code.
Use the same rules locally, in your editor workflow, and in CI. Collie keeps the feedback close to the file that caused it.
Format without debate
Normalize indentation, alternatives, tokens, and blank lines. Check formatting in CI or preview a diff before changing a file.
collie fmt --diff parser.y
Report where you work
Choose readable terminal output, JSON, GitHub annotations, or SARIF for code scanning—without maintaining separate rule sets.
collie lint --format sarif parser.y
No setup required
Bring a grammar.
Leave with a cleaner one.
Open the browser playground to lint, format, and auto-correct a grammar immediately. Ruby runs locally through WebAssembly, so your source never leaves the browser.
Open the browser playgroundYour grammar is source code.
Treat it like source code.
Install Collie, run it on a .y file, and make parser feedback useful before the build breaks.