Config Cheat Sheet

This cheat sheet provides a concise overview of ast-grep's linter rule YAML configuration. It's designed as a handy reference for common usage.

Basic Information

Core details that identify and define your rule and miscellaneous keys for documentation and custom data.

ℹ️ Basic Information
id: no-console-log	🆔 A unique, descriptive identifier for the rule.
language: JavaScript	🌐 The programming language the rule applies to.
url: 'https://doc.link/'	🔗 A URL to the rule's documentation.
metadata: { author: 'John Doe' }	📓 metadata A dictionary for custom data related to the rule.

Finding

Keys for specifying what code to search for.

🔍 Finding Code
rule: pattern: 'console.log($$$ARGS)'	🎯 The core rule to find matching AST nodes.
constraints: ARG: { kind: 'string' } }	⚙️ Additional constraints rules to filter meta-variable matches.
utils: is-react: kind: function_declaration has: { kind: jsx_element }	🛠️ A dictionary of reusable utility rules. Use them in matches to modularize your rules.

Patching

Keys for defining how to automatically fix the found code.

🛠️ Patching Code
transform: NEW_VAR: substring: {endChar: 1, source: $V}	🎩 transform meta-variables before they are used in fix.
transform: NEW_VAR: substring($V, endChar=1)	🎩 transform also accepts string form.
fix: "logger.log($$$ARGS)"	🔧 A fix string to auto-fix the matched code.
fix: template: "logger.log($$$ARGS)" expandEnd: rule	🔧 Fix also accepts FixConfig object.
rewriters: - id: remove-quotes rule: { pattern: "'$A'" } fix: "$A"	✍️ A list of rewriters for complex transformations.

Linting

Keys for configuring the messages and severity of reported issues.

🚦 Linting
severity: warning	⚠️ The severity level of the linting message.
message: "Avoid using $MATCH in production."	💬 A concise message explaining the rule. Matched $VAR can be used.
note: Use a _logger_ instead of `console`	📌 More detailed note. It supports Markdown format.
labels: ARG: style: 'primary' message: 'The argument to log'	🎨 Customized labels for highlighting parts of the matched code.
files: ['src/**/*.js']	✅ Glob files patterns to include files for the rule.
ignores: ['test/**/*.js']	❌ Glob patterns to exclude files from the rule.