babel-codemod

babel-codemod rewrites JavaScript and TypeScript using babel plugins.

Install

Install from yarn:

$ yarn global add babel-codemod

NOTE: You can also install using npm install -g babel-codemod.

This will install the runner as codemod. This package requires node v6 or higher.

Usage

The primary interface is as a command line tool, usually run like so:

$ codemod --plugin transform-module-name \
  path/to/file.js \
  another/file.js \
  a/directory

This will re-write the files path/to/file.js, another/file.js, and any supported files found in a/directory by transforming them with the babel plugin transform-module-name. Multiple plugins may be specified, and multiple files or directories may be re-written at once.

Note that TypeScript support is provided by babel and therefore may not completely support all valid TypeScript code. If you encounter an issue, consider looking for it in the babel issues labeled area: typescript before filing an issue with babel-codemod.

Plugins may also be loaded from remote URLs, including saved AST Explorer URLs, using --remote-plugin. This feature should only be used as a convenience to load code that you or someone you trust wrote. It will run with your full user privileges, so please exercise caution!

$ codemod --remote-plugin URL …

By default, babel-codemod makes minimal changes to your source files by using recast to parse and print your code, retaining the original comments and formatting. If desired, you can reformat files using Prettier by using --printer prettier. Note that this is typically only desired in projects that use Prettier, or if you plan on adopting Prettier.

For more detailed options, run codemod --help.

Writing a Plugin

There are many, many existing plugins that you can use. However, if you need to write your own you should consult the babel handbook. If you publish a plugin intended specifically as a codemod, consider using both the babel-plugin and babel-codemod keywords.

Transpiling using babel plugins

babel-codemod also supports non-standard/future language features that are not currently supported by the latest version of node. It does this by leveraging @babel/preset-env which loads the latest babel plugins. This feature is on by default.

This feature should support most use cases when writing plugins in advanced JavaScript syntax. However, if you are writing plugins with syntax that is beyond "latest", or you would like to use your own set of plugins and presets, you can pass in the --find-babel-config switch in combination with a local .babelrc file that lists the presets/plugins you want applied to your plugin code.

# Run a local plugin that is passed through locally installed babel plugins
$ codemod --find-babel-config --plugin ./my-plugin.js src/

This requires that all babel plugins and presets be installed locally and are listed in your .babelrc file. babel-codemod uses @babel/core under the hood to accomplish this and all .babelrc lookup rules apply.

Transpiling using TypeScript

There is experimental support for running plugins written in TypeScript. This is on by default and works by using @babel/preset-typescript rather than the official TypeScript compiler. This feature may be removed in the future.

For example:

# Run a local plugin written with TypeScript.
$ codemod --plugin ./my-plugin.ts src/

Contributing

See CONTRIBUTING.md for information on setting up the project for development and on contributing to the project.

Status

License

Copyright 2017 Square, Inc.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.