Modster

Codemoding, the easy way.

Modster is a plugin system and CLI for consuming and executing jscodeshift codemods, in a way that is not terrible.

In Modster, you pick your codemod from a list of codemods, answer a few questions to have it configured, choose a file or directory to run against - and off you go!

Easy? Yes, much. ✌️

See the full run.

Installation

E.g. using yarn:

$ yarn install modster
$ yarn modster

Configuration

.codemods.js

Modster is configured via a configuration file, typically named .codemods.js. It is expected to export an object with the following fields:

Field	Type	Required	Description
packageManager	string	✅	Your package manager; typically yarn or npm.
sourceDirectory	string	✅	The directory on which you want codemods to operate. You can further limit the scope of a codemod when running Modster.
extensions	string[]	✅	The file extensions you want to run codemods against. Passed to jscodeshift as the --ext option.
parser	string	✅	The parser to use for parsing source files. One of babel | babylon | flow | ts | tsx. Passed to jscodeshift as the --parser option.
plugins	string[]	✅	A list of Modster plugins, following the eslint-style plugin naming convention. See below for a list of existing plugins and how to create your own plugins.
postUpdateTasks	function		A function of the shape (updatedFiles: string[]) => { name: string; cmd: string }[], receiving the list of files modified by a codemod, and return a list of tasks to be executed. Every task has a name (e.g. prettier) and a command to be executed (e.g. yarn run prettier ...).

Like so.

  export default {
      packageManager: 'yarn',
      extensions: ['tsx', 'ts'],
      sourceFolder: 'src',
      parser: 'tsx',
      plugins: [
          'hello-world'
      ],
      postUpdateTask: (files: string[]) => [
          {
              name: 'eslint autofix',
              command: `yarn eslint ${files.join(' ')} --ext tsx,ts --fix`
          }
      ]
  }

CLI options

Modster takes two optional CLI options, --config <path-to-file>, and --dry.

Option	Description
--config <path-to-file>	The path to Modster's configuration file, relative to process.cwd(). Defaults to ./codemods.
--dry	If set, runs jscodeshift in a dry run. Post-update tasks are printed but not executed.

Plugins

Modster uses a plugin system to consume codemods, similar to how e.g. eslint consumes linting rules. It is important to understand that Modser comes with no built-in codemod functionality; running Modster without plugins therefore doesn't make a huge amount of sense. But good news! - using and even writing Modster plugins is dead simple:

Existing plugins

To consume a Modster plugin, you simply install it as an npm package, e.g. using yarn:

$ yarn install modster-plugin-hello-world

... and add it to your .codemods.js, following the eslint-style plugin naming convention:

module.exports = {
    // ...
    plugins: [
        // ...
+      'hello-world'
    ]
}

See below for a list of Modster plugins:

Plugin	Description
Hello World	A minimal plugin example; mostly a reference for developing new plugins.

To add a plugin to this list, please raise a PR.

Developing plugins

See Developing Modster plugins.

Contributions

Yes please!