jscodemigrate's Introduction

Migrate your code like you do with your database!

This is a simple wrapper around jscodeshift that give you a migration like interface.

Install in your project: npm install jscodemigrate --save-dev

Generate your first codemod:

jscodemigrate g switch-to-es6-classes

And you're off! Look in codemods/ to see your newly generated jscodemigration.

I would recommended taking a look at the template, and also js-codemod for ideas.

Pull in codemigrations from npm dependencies

jscodemigrate deps

Differences from writing jscodeshift

module.exports = {
  // Function to export is called transform
  transform: ({file, root, api, options}) => {
    // All the variables are passed in an options hash
    // Included with the usually is a root variable
    // (so that each migration doens't need to reparse the file)
    const j = api.jscodeshift;
    const {expression, statement, statements} = j.template;

    const printOptions = options.printOptions || {};

    const didTransform = true;
    
    root.find(j.Identifier).replaceWith(
      p => j.identifier(p.node.name.split('').reverse().join(''))
    )
    
    // You'll notice a return hash instead of the usual resulting source string
    return {
      didTransform,
      root,
      printOptions
    };
  }
}

Configuration

.codemodrc file

{ // These options mostly mirror jscodeshift's command line args
  "paths": [ "src/", "tests/", "special/file.js" ], // Paths to search when doing codemods
  "extensions": "js,es6" // Comma separated extensions to consider
}

Per code migration config

module.exports = {
  moduleApiChange: true, // Tell jscodemigrate to pull this into dependencies
  paths: [ "tests/" ], // even if your .codemodrc file looks in all your files, this will only run in 'tests/' directory
  // Tranform is the only thing that isn't optional
  transform: ({file, root, api, options}) => {
    ...
  }
}