Syntax-tree pattern rules

Some conventions belong to one project, and no stock linter knows them. This tool writes them as code patterns matched against the syntax tree, so a rule sees the structure of the code rather than its text, in any language the tool can parse.

Finding it

Look for the rule files in the repository (an sgconfig.yml and its rule directories for ast-grep, a directory of YAML rules for Semgrep) and in CI or the pre-commit config for the step that runs them.

Using it

• Run them: ast-grep scan, or semgrep scan --config <rules>; on changed files while working, on everything in CI.
• Test every rule: each rule is kept with examples that must match and examples that must not, run as tests of the rule (ast-grep test, semgrep --test).
• Say how to fix: the rule's message names the fix, not only the problem.

Examples: ast-grep, Semgrep custom rules.