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Tool Ast Grep Rules by tomevault-io

Name: Tool Ast Grep Rules
Author: tomevault-io

Tool Ast Grep Rules

Write AST-based code search and rewrite rules using ast-grep YAML. Create linting rules, code modernizations, and API migrations with auto-fix. Use when the user mentions ast-grep, tree-sitter patterns, code search rules, lint rules with YAML, AST matching, or code refactoring patterns. Use when this capability is needed.

tomevault-io Updated Sep 17, 2026

File contents

ast-grep Rule Crafter

ast-grep uses tree-sitter to parse code into AST, enabling precise pattern matching. Rules are defined in YAML for linting, searching, and rewriting code.

Quick Start

id: no-console-log
language: JavaScript
rule:
  pattern: console.log($$$ARGS)
fix: logger.log($$$ARGS)
message: Replace console.log with logger

Project Configuration

Project-level scanning requires an sgconfig.yml configuration file:

# sgconfig.yml (project root)
ruleDirs:
  - rules          # Rule directory, recursively loads all .yml files

Typical project structure:

my-project/
├── sgconfig.yml
├── rules/
│   ├── no-console.yml
│   └── custom/
│       └── team-rules.yml
└── src/

Running project scan:

ast-grep scan              # Automatically finds sgconfig.yml
ast-grep scan --config path/to/sgconfig.yml  # Specify config

Note: ast-grep scan command requires sgconfig.yml, while ast-grep run -p can be used standalone.

Rule Workflow

Lint Rule (Common)

Check only without fixing, used for CI/editor hints:

# rules/no-console-log.yml
id: no-console-log
language: JavaScript
severity: warning
message: Avoid console.log in production code
rule:
  pattern: console.log($$$ARGS)

Verify:

ast-grep scan -r rules/no-console-log.yml src/

Rewrite Rule (Optional)

Add fix when auto-fix is needed:

id: no-console-log
language: JavaScript
severity: warning
message: Replace console.log with logger
rule:
  pattern: console.log($$$ARGS)
fix: logger.log($$$ARGS)

Apply fix:

ast-grep scan -r rules/no-console-log.yml --update-all src/

Development Workflow

- [ ] 1. Explore pattern with CLI: ast-grep -p 'pattern' src/
- [ ] 2. Create rule file (.yml)
- [ ] 3. Verify: ast-grep scan -r rule.yml src/
- [ ] 4. If false positives → add constraints → re-verify

Debug AST structure:

ast-grep -p 'console.log($ARG)' --debug-query ast

Essential Syntax

Element	Syntax	Example
Single node	`$VAR`	`console.log($MSG)`
Multiple nodes	`$$$ARGS`	`fn($$$ARGS)`
Same content	Use same name	`$A == $A`
Non-capturing	`$_VAR`	`$_FN($_FN)`

Core Rules Quick Reference

Type	Purpose	Example
`pattern`	Match code structure	`pattern: if ($COND) {}`
`kind`	Match AST node type	`kind: function_declaration`
`all`	Match ALL conditions	`all: [pattern: X, kind: Y]`
`any`	Match ANY condition	`any: [pattern: var $A, pattern: let $A]`
`not`	Exclude matches	`not: {pattern: safe_call()}`
`has`	Must have child	`has: {kind: return_statement}`
`inside`	Must be in ancestor	`inside: {kind: class_body}`

Detailed References

Complete syntax guide: See rule-syntax.md

Atomic rules (pattern, kind, regex, nthChild, range)
Composite rules (all, any, not, matches)
Relational rules (has, inside, follows, precedes)
Transform and fixConfig

Language-specific patterns: See common-patterns.md

JavaScript/TypeScript examples
Python examples
Go and Rust examples

Supported Languages

Bash, C, Cpp, CSharp, Css, Elixir, Go, Haskell, Hcl, Html, Java, JavaScript, Json, Kotlin, Lua, Nix, Php, Python, Ruby, Rust, Scala, Solidity, Swift, Tsx, TypeScript, Yaml

Converted and distributed by TomeVault — claim your Tome and manage your conversions.

---name: tool-ast-grep-rulesdescription: Write AST-based code search and rewrite rules using ast-grep YAML. Create linting rules, code modernizations, and API migrations with auto-fix. Use when the user mentions ast-grep, tree-sitter patterns, code search rules, lint rules with YAML, AST matching, or code refactoring patterns. Use when this capability is needed.---# ast-grep Rule Crafterast-grep uses tree-sitter to parse code into AST, enabling precise pattern matching. Rules are defined in YAML for linting, searching, and rewriting code.## Quick Start```yamlid: no-console-loglanguage: JavaScriptrule: pattern: console.log($$$ARGS)fix: logger.log($$$ARGS)message: Replace console.log with logger```## Project ConfigurationProject-level scanning requires an `sgconfig.yml` configuration file:```yaml# sgconfig.yml (project root)ruleDirs: - rules # Rule directory, recursively loads all .yml files```Typical project structure:```my-project/├── sgconfig.yml├── rules/│ ├── no-console.yml│ └── custom/│ └── team-rules.yml└── src/```Running project scan:```bashast-grep scan # Automatically finds sgconfig.ymlast-grep scan --config path/to/sgconfig.yml # Specify config```> **Note**: `ast-grep scan` command requires `sgconfig.yml`, while `ast-grep run -p` can be used standalone.## Rule Workflow### Lint Rule (Common)Check only without fixing, used for CI/editor hints:```yaml# rules/no-console-log.ymlid: no-console-loglanguage: JavaScriptseverity: warningmessage: Avoid console.log in production coderule: pattern: console.log($$$ARGS)```Verify:```bashast-grep scan -r rules/no-console-log.yml src/```### Rewrite Rule (Optional)Add `fix` when auto-fix is needed:```yamlid: no-console-loglanguage: JavaScriptseverity: warningmessage: Replace console.log with loggerrule: pattern: console.log($$$ARGS)fix: logger.log($$$ARGS)```Apply fix:```bashast-grep scan -r rules/no-console-log.yml --update-all src/```### Development Workflow```- [ ] 1. Explore pattern with CLI: ast-grep -p 'pattern' src/- [ ] 2. Create rule file (.yml)- [ ] 3. Verify: ast-grep scan -r rule.yml src/- [ ] 4. If false positives → add constraints → re-verify```Debug AST structure:```bashast-grep -p 'console.log($ARG)' --debug-query ast```## Essential Syntax| Element | Syntax | Example ||---------|--------|---------|| Single node | `$VAR` | `console.log($MSG)` || Multiple nodes | `$$$ARGS` | `fn($$$ARGS)` || Same content | Use same name | `$A == $A` || Non-capturing | `$_VAR` | `$_FN($_FN)` |## Core Rules Quick Reference| Type | Purpose | Example ||------|---------|---------|| `pattern` | Match code structure | `pattern: if ($COND) {}` || `kind` | Match AST node type | `kind: function_declaration` || `all` | Match ALL conditions | `all: [pattern: X, kind: Y]` || `any` | Match ANY condition | `any: [pattern: var $A, pattern: let $A]` || `not` | Exclude matches | `not: {pattern: safe_call()}` || `has` | Must have child | `has: {kind: return_statement}` || `inside` | Must be in ancestor | `inside: {kind: class_body}` |## Detailed References**Complete syntax guide**: See [rule-syntax.md](rule-syntax.md)- Atomic rules (pattern, kind, regex, nthChild, range)- Composite rules (all, any, not, matches)- Relational rules (has, inside, follows, precedes)- Transform and fixConfig**Language-specific patterns**: See [common-patterns.md](common-patterns.md)- JavaScript/TypeScript examples- Python examples- Go and Rust examples## Supported LanguagesBash, C, Cpp, CSharp, Css, Elixir, Go, Haskell, Hcl, Html, Java, JavaScript, Json, Kotlin, Lua, Nix, Php, Python, Ruby, Rust, Scala, Solidity, Swift, Tsx, TypeScript, Yaml---> Converted and distributed by [TomeVault](https://tomevault.io/claim/heyvhuang) — claim your Tome and manage your conversions.

Frequently asked questions