# Ast Grep

> Thank you for your interest in adding a new language to ast-grep!

## Pages

- [Add New Language to ast-grep](add-lang.md): Thank you for your interest in adding a new language to ast-grep!
- [API Usage](api-usage.md): ast-grep allows you to craft complicated rules, but it is not easy to do arbitrary AST manipulation.
- [API Reference](api.md): ast-grep currently has an experimental API for [Node.js](https://nodejs.org/).
- [Atomic Rule](atomic-rule.md): ast-grep has three categories of rules. Let's start with the most basic one: atomic rule.
- [Avoid Duplicated Exports](avoid-duplicated-exports.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InJ1c3QiLCJxdWVyeSI6IiIsImNvbmZpZyI6InJ1bGU6XG4g...
- [Avoid Jsx Short Circuit](avoid-jsx-short-circuit.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InRzeCIsInF1ZXJ5IjoiY29uc29sZS5sb2coJE1BVENIKSIs...
- [Avoid Nested Links](avoid-nested-links.md): * [Playground Link](https://ast-grep.github.io/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InRzeCIsInF1ZXJ5IjoiaW...
- [Boshen Footgun](boshen-footgun.md): * [Playground Link](https://ast-grep.github.io/playground.html#eyJtb2RlIjoiUGF0Y2giLCJsYW5nIjoicnVzdCIsInF1ZXJ5IjoiJE...
- [C](c.md): This page curates a list of example ast-grep rules to check and to rewrite C code.
- [Command Line Reference](cli.md): You can always see up-to-date command line options using`ast-grep --help`.
- [Composite Rule](composite-rule.md): Composite rule can accept another rule or a list of rules recursively.
- [Core Concepts in ast-grep's Pattern](core-concepts.md): One key highlight of ast-grep is its pattern.
- [Cpp](cpp.md): This page curates a list of example ast-grep rules to check and to rewrite Cpp code.
- [Custom Language Support](custom-language.md): In this guide, we will show you how to use a custom language that is not built into ast-grep.
- [Defer Func Call Antipattern](defer-func-call-antipattern.md): * [Playground Link](/playground.html#eyJtb2RlIjoiUGF0Y2giLCJsYW5nIjoiZ28iLCJxdWVyeSI6InsgXG4gICAgZGVmZXIgJEEuJEIodCwg...
- [Pattern 1: Rails.root.join with variable](detect-path-traversal.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InJ1YnkiLCJxdWVyeSI6IiIsInJld3JpdGUiOiIiLCJzdHJp...
- [Development Guide](development.md): ast-grep is written in [Rust](https://www.rust-lang.org/) and hosted by [git](https://git-scm.com/).
- [Editor Integration](editors.md): ast-grep is a **command line tool** for structural search/replace. But it can be readily integrated into your editors...
- [Ensure Clean Architecture](ensure-clean-architecture.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6ImtvdGxpbiIsInF1ZXJ5IjoiIiwicmV3cml0ZSI6IiIsInN0...
- [Extract I18N Key](extract-i18n-key.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6Imh0bWwiLCJxdWVyeSI6IiIsInJld3JpdGUiOiIiLCJzdHJp...
- [Frequently Asked Questions](faq.md): 1. **Use the Playground**: Test your pattern in the [ast-grep playground](/playground.html).
- [Find Field With Type](find-field-with-type.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6ImphdmEiLCJxdWVyeSI6ImAkVEFHYCIsInJld3JpdGUiOiIi...
- [Find Func Declaration With Prefix](find-func-declaration-with-prefix.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6ImdvIiwicXVlcnkiOiJyJ15bQS1aYS16MC05Xy1dKyciLCJy...
- [Find Import File Without Extension](find-import-file-without-extension.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6ImphdmFzY3JpcHQiLCJxdWVyeSI6ImNvbnNvbGUubG9nKCRN...
- [find-all-imports-and-identifiers.yaml](find-import-identifiers.md): * [Playground Link](https://ast-grep.github.io/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InR5cGVzY3JpcHQiLCJxdW...
- [Find Import Usage](find-import-usage.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InR5cGVzY3JpcHQiLCJxdWVyeSI6IiIsInJld3JpdGUiOiIi...
- [Find Key Value](find-key-value.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InlhbWwiLCJxdWVyeSI6IiIsInJld3JpdGUiOiIiLCJzdHJp...
- [Find & Patch: A Novel Functional Programming like Code Rewrite Scheme](find-n-patch.md): Code transformation is a powerful technique that allows you to modify your code programmatically. There are many tool...
- [Find Struct Inheritance](find-struct-inheritance.md): * [Playground Link](/playground.html#eyJtb2RlIjoiUGF0Y2giLCJsYW5nIjoiY3BwIiwicXVlcnkiOiJzdHJ1Y3QgJFNPTUVUSElORzogICRJ...
- [Fix Format Vuln](fix-format-vuln.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6ImNwcCIsInF1ZXJ5IjoiIiwicmV3cml0ZSI6IiIsInN0cmlj...
- [Fix](fix.md): ast-grep has two kinds of fixes:`string`and`FixConfig`.
- [Get Digit Count In Usize](get-digit-count-in-usize.md): * [Playground Link](/playground.html#eyJtb2RlIjoiUGF0Y2giLCJsYW5nIjoicnVzdCIsInF1ZXJ5IjoiJE5VTS50b19zdHJpbmcoKS5jaGFy...
- [Go](go.md): This page curates a list of example ast-grep rules to check and to rewrite Go code.
- [How ast-grep Works: A bird's-eye view](how-ast-grep-works.md): In the world of software development, efficiently searching, rewriting, linting, and analyzing code is essential for ...
- [Contributing](how-to.md): :tada: ***We are thrilled that you are interested in contributing to the ast-grep project!*** :tada:
- [HTML](html.md): This page curates a list of example ast-grep rules to check and to rewrite HTML code.
- [Java](java.md): This page curates a list of example ast-grep rules to check and to rewrite Java code.
- [JavaScript API](js-api.md): Powered by [napi.rs](https://napi.rs/), ast-grep's JavaScript API enables you to write JavaScript to programmatically...
- [JSON Mode](json.md): Composability is a key perk of command line tooling. ast-grep is no exception.
- [Kotlin](kotlin.md): This page curates a list of example ast-grep rules to check and to rewrite Kotlin code.
- [Search Multi-language Documents in ast-grep](language-injection.md): ast-grep works well searching files of one single language, but it is hard to extract a sub language embedded inside ...
- [List of Languages with Built-in Support](languages.md): The table below lists all languages that are supported by ast-grep.
- [Lint Rule](lint-rule.md): A lint rule is a configuration file that specifies how to find, report and fix issues in the codebase.
- [Deep Dive into ast-grep's Match Algorithm](match-algorithm.md): By default, ast-grep uses a smart strategy to match pattern against the AST node. All nodes in the pattern must be ma...
- [Match Function Call](match-function-call.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6ImMiLCJxdWVyeSI6InRlc3QoJCQkKSIsInJld3JpdGUiOiIi...
- [Match Package Import](match-package-import.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6ImdvIiwicXVlcnkiOiIiLCJyZXdyaXRlIjoiIiwic3RyaWN0...
- [Migrate Action Filter](migrate-action-filter.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InJ1YnkiLCJxdWVyeSI6ImNvbnNvbGUubG9nKCRNQVRDSCki...
- [Migrate Openai Sdk](migrate-openai-sdk.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InB5dGhvbiIsInF1ZXJ5IjoiZGVmICRGVU5DKCQkJEFSR1Mp...
- [Migrate Xstate V5](migrate-xstate-v5.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6ImphdmFzY3JpcHQiLCJxdWVyeSI6ImlmICgkQSkgeyAkJCRC...
- [Missing Component Decorator](missing-component-decorator.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6ImphdmFzY3JpcHQiLCJxdWVyeSI6ImltcG9ydCAkQSBmcm9t...
- [`ast-grep new`](new.md): Create new ast-grep project or items like rules/tests. Also see the step by step [guide](/guide/scan-project.html).
- [No Await In Promise All](no-await-in-promise-all.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6ImphdmFzY3JpcHQiLCJxdWVyeSI6ImNvbnNvbGUubG9nKCRN...
- [No Console Except Catch](no-console-except-catch.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6ImphdmFzY3JpcHQiLCJxdWVyeSI6ImlmICRBLmhhc19mZWF0...
- [No Unused Vars](no-unused-vars.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6ImphdmEiLCJxdWVyeSI6ImlmKHRydWUpeyQkJEJPRFl9Iiwi...
- [Optional To None Union](optional-to-none-union.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InB5dGhvbiIsInF1ZXJ5IjoiIiwicmV3cml0ZSI6IiIsInN0...
- [Deep Dive into ast-grep's Pattern Syntax](pattern-parse.md): ast-grep's pattern is easy to learn but hard to master. While it's easy to get started with, mastering its nuances ca...
- [Pattern Syntax](pattern-syntax.md): In this guide we will walk through ast-grep's pattern syntax. The example will be written in JavaScript, but the basi...
- [Performance Tip for napi usage](performance-tip.md): Using`napi`to parse code and search for nodes [isn't always faster](https://medium.com/@hchan_nvim/benchmark-typesc...
- [ast-grep Playground Manual](playground.md): The [ast-grep playground](/playground.html) is an online tool that allows you to try out ast-grep without installing ...
- [Prefer Generator Expressions](prefer-generator-expressions.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InB5dGhvbiIsInF1ZXJ5IjoiWyQkJEFdIiwicmV3cml0ZSI6...
- [Prefer Symbol Over Proc](prefer-symbol-over-proc.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InJ1YnkiLCJxdWVyeSI6IiRMSVNULnNlbGVjdCB7IHwkVnwg...
- [Project Configuration](project-config.md): ast-grep supports using [YAML](https://yaml.org/) to configure its linting rules to scan your code repository.
- [Using ast-grep with AI Tools](prompting.md): This guide outlines several existing methods for leveraging AI with ast-grep.
- [Python API](py-api.md): ast-grep's Python API is powered by [PyO3](https://pyo3.rs/).
- [Python](python.md): This page curates a list of example ast-grep rules to check and to rewrite Python code.
- [Quick Start](quick-start.md): You can unleash`ast-grep`'s power at your fingertips in a few keystrokes on the command line!
- [Redundant Unsafe Function](redundant-unsafe-function.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InJ1c3QiLCJxdWVyeSI6IntcbiAgZGVzY3JpcHRpb24gPSAk...
- [Redundant Usestate Type](redundant-usestate-type.md): * [Playground Link](/playground.html#eyJtb2RlIjoiUGF0Y2giLCJsYW5nIjoidHlwZXNjcmlwdCIsInF1ZXJ5IjoidXNlU3RhdGU8c3RyaW5n...
- [Refactor Pytest Fixtures](refactor-pytest-fixtures.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InB5dGhvbiIsInF1ZXJ5IjoiZGVmIGZvbygkWCk6XG4gICRT...
- [Relational Rules](relational-rule.md): Atomic rule can only match the target node directly. But sometimes we want to match a node based on its surrounding n...
- [define a rewriter to remove the await keyword](remove-async-await.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InB5dGhvbiIsInF1ZXJ5IjoiYXdhaXQgJCQkQ0FMTCIsInJl...
- [Rename Svg Attribute](rename-svg-attribute.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InRzeCIsInF1ZXJ5IjoiIiwicmV3cml0ZSI6IiIsInN0cmlj...
- [Reverse React Compiler](reverse-react-compiler.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InRzeCIsInF1ZXJ5IjoiIiwicmV3cml0ZSI6IiIsInN0cmlj...
- [Rewrite Code](rewrite-code.md): One of the powers of ast-grep is that it can not only find code patterns, but also transform them into new code.
- [Rewrite Indoc Macro](rewrite-indoc-macro.md): * [Playground Link](/playground.html#eyJtb2RlIjoiUGF0Y2giLCJsYW5nIjoicnVzdCIsInF1ZXJ5IjoiaW5kb2MhIHsgciNcIiQkJEFcIiMg...
- [Rewrite Method To Function Call](rewrite-method-to-function-call.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6ImMiLCJxdWVyeSI6IiRDT1VOVCA9ICRcbiIsInJld3JpdGUi...
- [Rewrite Mobx Component](rewrite-mobx-component.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6ImphdmFzY3JpcHQiLCJxdWVyeSI6ImNvbnNvbGUubG9nKCRN...
- [Should not be transformed](rewrite-sqlalchemy-mapped-column.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InB5dGhvbiIsInF1ZXJ5IjoiYShudWxsYWJsZT1UcnVlKSIs...
- [Rewriter in Fix](rewriter.md): `rewriters`allow you to apply rules to specific parts of the matching AST nodes.
- [TODO:](roadmap.md): * \[x] Add replace
- [Ruby](ruby.md): This page curates a list of example ast-grep rules to check and to rewrite Ruby applications.
- [Rule Essentials](rule-config.md): Now you have learnt the basic of ast-grep's pattern syntax and searching.
- [or without fixer](rule-template.md): * [Playground Link](/playground.html#)
- [Rule Cheat Sheet](rule.md): This cheat sheet provides a concise overview of ast-grep's rule object configuration, covering Atomic, Relational, an...
- [`ast-grep run`](run.md): Run one time search or rewrite in command line.
- [Rust](rust.md): This page curates a list of example ast-grep rules to check and to rewrite Rust applications.
- [Scan Your Project!](scan-project.md): Let's explore its power to run scan on your code repository in a scalable way!
- [`ast-grep scan`](scan.md): Scan and rewrite code by configuration.
- [Handle Error Reports](severity.md): ast-grep supports these severity levels for rules:
- [`sgconfig.yml` Reference](sgconfig.md): To scan a project with multiple rules, you need to specify the root of a project by maintaining a`sgconfig.yml`file.
- [find the barrel import statement](speed-up-barrel-import.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6ImphdmFzY3JpcHQiLCJxdWVyeSI6IiIsInJld3JpdGUiOiIi...
- [Switch From Should To Expect](switch-from-should-to-expect.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InJ1c3QiLCJxdWVyeSI6IiIsInJld3JpdGUiOiIiLCJzdHJp...
- [Test Your Rule](test-rule.md): Though it is easy to write a simple rule to match some code in ast-grep, writing a robust and comprehensive rule to c...
- [`ast-grep test`](test.md): Test ast-grep rules.
- [Comparison With Other Frameworks](tool-comparison.md): :::danger Disclaimer
- [Command Line Tooling Overview](tooling-overview.md): ast-grep's tooling supports multiple stages of your development. Here is a list of the tools and their purpose:
- [`transform` Code in Rewrite](transform.md): Sometimes, we may want to apply some transformations to the meta variables in the fix part of a YAML rule. For exampl...
- [Transformation Object](transformation.md): A transformation object is used to manipulate meta variables. It is a dictionary with the following structure:
- [TSX](tsx.md): This page curates a list of example ast-grep rules to check and to rewrite TypeScript with JSX syntax.
- [TypeScript](typescript.md): This page curates a list of example ast-grep rules to check and to rewrite TypeScript applications.
- [Unmarshal Tag Is Dash](unmarshal-tag-is-dash.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6ImdvIiwicXVlcnkiOiJgJFRBR2AiLCJyZXdyaXRlIjoiIiwi...
- [Unnecessary React Hook](unnecessary-react-hook.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6ImphdmFzY3JpcHQiLCJxdWVyeSI6IiIsInJld3JpdGUiOiIi...
- [ensure it only matches modal/tooltip but not tag](upgrade-ant-design-vue.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6Imh0bWwiLCJxdWVyeSI6IiIsInJld3JpdGUiOiIiLCJzdHJp...
- [Use Logical Assignment](use-logical-assignment.md): * [Playground Link](/playground.html#eyJtb2RlIjoiUGF0Y2giLCJsYW5nIjoiamF2YXNjcmlwdCIsInF1ZXJ5IjoiJEEgPSAkQSB8fCAkQiIs...
- [Use Walrus Operator In If](use-walrus-operator-in-if.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6InB5dGhvbiIsInF1ZXJ5IjoiZm4gbWFpbigpIHsgXG4gICAg...
- [Reusing Rule as Utility](utility-rule.md): ast-grep chooses to use YAML for rule representation. While this decision makes writing rules easier, it does impose ...
- [YAML](yaml.md): This page curates a list of example ast-grep rules to check and to rewrite YAML code.
- [Yoda Condition](yoda-condition.md): * [Playground Link](/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6ImMiLCJxdWVyeSI6IiRDOiAkVCA9IHJlbGF0aW9uc2hpcCgk...