ast-grep

How CodeRabbit runs ast-grep to find code patterns and report rule matches in pull requests.

ast-grep is an open-source static analysis tool that uses abstract syntax trees (AST) to find patterns in your codebase, helping identify security vulnerabilities and enforce code quality standards. CodeRabbit runs ast-grep on supported changed files using the essentials package and any custom rules you configure.

CodeRabbit runs ast-grep v0.45.3.

Configuration

enabled · boolean · default: true

Enable ast-grep

rule_dirs · array of string · default: []

List of rules directories.

util_dirs · array of string · default: []

List of utils directories.

essential_rules · boolean · default: true

Use ast-grep essentials package.

packages · array of string · default: []

Predefined packages to be used.

.coderabbit.yaml

.coderabbit.yaml

reviews:
  tools:
    ast-grep:
      enabled: true
      rule_dirs: []
      util_dirs: []
      essential_rules: true
      packages: []

Web UI

In your organization or repository settings, go to Reviews → Tools and turn the tool on or off with its toggle. To change its other settings, click the settings icon next to the toggle.

rule_dirs lists directories with your custom ast-grep rules, and util_dirs lists directories with utility configs that support rule management. Both take paths relative to the repository root. packages takes GitHub repositories in owner/repository format.

CodeRabbit ignores rule_dirs and util_dirs entries that do not exist in the review checkout, use absolute paths or parent-directory traversal, or contain control or shell-sensitive characters.

CodeRabbit will only run ast-grep if you have configured at least one of the following:

• Custom rule directories (rule_dirs)
• Essential rules enabled (essential_rules: true)
• Custom packages (packages)

util_dirs can be used to support shared utility configs, but by itself it does not cause ast-grep to run.

CodeRabbit also skips ast-grep when the pull request contains no changed files with a supported extension. Individual files that are 8 MiB or larger are skipped.

Links

• ast-grep Documentation
• Writing ast-grep Rules
• ast-grep Rule Object Properties
• ast-grep Essentials Package

Files

ast-grep runs on changed files with the following extensions:

• .bash
• .c
• .cpp
• .cs
• .css
• .erb (parsed as HTML)
• .ex
• .exs
• .go
• .h
• .hpp
• .hs
• .html
• .java
• .js
• .json
• .jsx
• .kt
• .lua
• .php
• .py
• .rb
• .rs
• .scala
• .sh
• .sql
• .swift
• .ts
• .tsx
• .yaml
• .yml