index01d / react-codemod

React codemod scripts

react-codemod

This repository contains a collection of codemod scripts based for use with JSCodeshift that help update React APIs.

Setup & Run

• npm install -g jscodeshift
• git clone https://github.com/reactjs/react-codemod.git or download a zip file from https://github.com/reactjs/react-codemod/archive/master.zip
• Run npm install in the react-codemod directory
• jscodeshift -t <codemod-script> <path>
• Use the -d option for a dry-run and use -p to print the output for comparison

Included Scripts

create-element-to-jsx

Converts calls to React.createElement into JSX elements.

jscodeshift -t react-codemod/transforms/create-element-to-jsx.js <path>

findDOMNode

Updates this.getDOMNode() or this.refs.foo.getDOMNode() calls inside of React.createClass components to React.findDOMNode(foo). Note that it will only look at code inside of React.createClass calls and only update calls on the component instance or its refs. You can use this script to update most calls to getDOMNode and then manually go through the remaining calls.

jscodeshift -t react-codemod/transforms/findDOMNode.js <path>

manual-bind-to-arrow

Converts manual function bindings in a class (e.g., this.f = this.f.bind(this)) to arrow property initializer functions (e.g., f = () => {}).

jscodeshift -t react-codemod/transforms/manual-bind-to-arrow.js <path>

pure-component

jscodeshift -t react-codemod/transforms/pure-component.js <path>

pure-render-mixin

Removes PureRenderMixin and inlines shouldComponentUpdate so that the ES2015 class transform can pick up the React component and turn it into an ES2015 class. NOTE: This currently only works if you are using the master version (>0.13.1) of React as it is using React.addons.shallowCompare

jscodeshift -t react-codemod/transforms/pure-render-mixin.js <path>

• If --mixin-name=<name> is specified it will look for the specified name instead of PureRenderMixin. Note that it is not possible to use a namespaced name for the mixin. mixins: [React.addons.PureRenderMixin] will not currently work.

react-to-react-dom

Updates code for the split of the react and react-dom packages (e.g., React.render to ReactDOM.render). It looks for require('react') and replaces the appropriate property accesses using require('react-dom'). It does not support ES6 modules or other non-CommonJS systems. We recommend performing the findDOMNode conversion first.

jscodeshift -t react-codemod/transforms/react-to-react-dom.js <path>

• After running the automated codemod, you may want to run a regex-based find-and-replace to remove extra whitespace between the added requires, such as codemod.py -m -d src --extensions js '(var React\s*=\s*require\(.react.\);)\n\n(\s*var ReactDOM)' '\1\n\2' using https://github.com/facebook/codemod.

sort-comp

Reorders React component methods to match the ESLint react/sort-comp rule. (Defaults to ordering of the Airbnb style guide.

jscodeshift -t react-codemod/transforms/sort-comp.js <path>

Explanation of the new ES2015 class transform with property initializers

1. Determine if mixins are convertible. We only transform a createClass call to an ES6 class component when:

• There are no mixins on the class, or
• options['pure-component'] is true, the mixins property is an array and it only contains pure render mixin (the specific module name can be specified using options['mixin-module-name'], which defaults to react-addons-pure-render-mixin)

2. Ignore components that:

• Call deprecated APIs. This is very defensive, if the script finds any identifiers called isMounted, getDOMNode, replaceProps, replaceState or setProps it will skip the component
• Explicitly call this.getInitialState() and/or this.getDefaultProps() since an ES6 class component will no longer have these methods
• Use arguments in methods since arrow functions don't have arguments. Also please notice that arguments should be very carefully used and it's generally better to switch to spread (...args) instead
• Have inconvertible getInitialState(). Specifically if you have variable declarations like var props = ... and the right hand side is not this.props then we can't inline the state initialization in the constructor due to variable shadowing issues
• Have non-primitive right hand side values (like foo: getStuff()) in the class spec

3. Transform it to an ES6 class component
4. Replace var A = React.createClass(spec) with class A extends React.Component {spec}. If a component uses pure render mixin and passes the mixins test (as described above), it will extend React.PureComponent instead - Remove the require/import statement that imports pure render mixin when it's no longer being referenced
5. Pull out all statics defined on statics plus the few special cased statics like childContextTypes, contextTypes, displayName, getDefaultProps(), and propTypes and transform them to static properties (static propTypes = {...};) - If getDefaultProps() is simple (i.e. it only contains a return statement that returns something) it will be converted to a simple assignment (static defaultProps = ...;). Otherwise an IIFE (immediately-invoked function expression) will be created (static defaultProps = function() { ... }();). Note that this means that the function will be executed only a single time per app-lifetime. In practice this hasn't caused any issues — getDefaultProps should not contain any side-effects
6. Transform getInitialState() - If there's no getInitialState() or the getInitialState() function is simple (i.e., it only contains a return statement that returns something) then we don't need a constructor; state will be lifted to a property initializer (state = ...;)
   • However, if the RHS of return contains references to this other than this.props and/or this.context, we can't be sure about what you'll need from this. We need to ensure that our property initializers' evaluation order is safe, so we defer state's initialization by moving it all the way down until all other property initializers have been initialized - If getInitialState() is not simple, we create a constructor and convert getInitialState() to an assignment to this.state
   • constructor always have props as the first parameter
   • We only put context as the second parameter when (one of) the following things happen in getInitialState():
     • It accesses this.context, or
     • There's a direct method call this.x(), or
     • this is referenced alone
   • Rewrite accesses to this.props to props and accesses to this.context to context since the values will be passed as constructor arguments
     • Remove simple variable declarations like var props = this.props; and var context = this.context
   • Rewrite top-level return statements (return {...};) to this.state = {...}
     • Add return; after the assignment when the return statement is part of a control flow statement (not a direct child of getInitialState()'s body) and not in an inner function declaration
7. Transform all non-lifecycle methods and fields to class property initializers (like onClick = () => {};). All your Flow annotations will be preserved - It's actually not necessary to transform all methods to arrow functions (i.e., to bind them), but this behavior is the same as createClass() and we can make sure that we won't accidentally break stuff
8. Generate Flow annotations from propTypes and put it on the class (this only happens when there's /* @flow */ in your code and options['flow'] is true)

• Flow actually understands propTypes in createClass calls but not ES6 class components. Here the transformation logic is identical to how Flow treats propTypes
• Notice that Flow treats an optional propType as non-nullable
  • For example, foo: React.PropTypes.number is valid when you pass {}, {foo: null}, or {foo: undefined} as props at runtime. However, when Flow infers type from a createClass call, only {} and {foo: undefined} are valid; {foo: null} is not. Thus the equivalent type annotation in Flow is actually {foo?: number}. The question mark on the left hand side indicates {} and {foo: undefined} are fine, but when foo is present it must be a number
• For propTypes fields that can't be recognized by Flow, $FlowFixMe will be used

Usage

jscodeshift -t ./transforms/class.js --mixin-module-name=react-addons-pure-render-mixin --flow=true --pure-component=true --remove-runtime-proptypes=false <path>

Recast Options

Options to recast's printer can be provided through the printOptions command line argument

jscodeshift -t transform.js <path> --printOptions='{"quote":"double"}'

Support and Contributing

The scripts in this repository are provided in the hope that they are useful, but they are not officially maintained, and we generally will not fix community-reported issues. They are a collection of scripts that were previously used internally within Facebook or were contributed by the community, and we rely on community contributions to fix any issues discovered or make any improvements. If you want to contribute, you're welcome to submit a pull request.