ts-transform-instrument-react-components

Note! This transformer is currently experimental

A TypeScript custom transformer that instruments React components to report which components exists in your bundle and which gets rendered. This information can then be used to optimize your bundle and load unrendered components lazily.

How to extract the information

This transformer modifies all files that contains components to define a global variable called reactInstrumentationDefinedComponents. This is an object with file names as key and array of exported names as value. It might look like this:

global.reactInstrumentationDefinedComponents = {
  'Component1.tsx': ['default', 'SomeOtherComponent']
}

Another variable of the same type is created which is called reactInstrumentationRenderedComponents. That will contain a list of the same type of objects of c omponents that have been rendered. So if only the default export from the previous example was rendered it would look like this:

global.reactInstrumentationRenderedComponents = {
  'Component1.tsx': ['default']
}

In order to know which components your file includes that doesn't get rendered you'd run this transform on your code, load the code in Node.js and call ReactDOM.renderToString() on your main components and then check the diff of reactInstrumentationDefinedComponents and reactInstrumentationRenderedComponents. You can of course also run the transformed code in the browser as well and view those global objects in the dev tools.

Other useful transform

If you find this transform useful you might want to use these ones as well: https://github.com/avensia-oss/ts-transform-export-const-folding and https://github.com/avensia-oss/ts-transform-async-import

Installation

yarn add @avensia-oss/ts-transform-instrument-react-components

Usage with webpack

Unfortunately TypeScript doesn't let you specifiy custom transformers in tsconfig.json. If you're using ts-loader with webpack you can specify it like this: https://github.com/TypeStrong/ts-loader#getcustomtransformers-----before-transformerfactory-after-transformerfactory--

The default export of this module is a function which expects a ts.Program an returns a transformer function. Your config should look something like this:

const instrumentReactComponentsTransform = require('@avensia-oss/ts-transform-instrument-react-components');

return {
  ...
  options: {
    getCustomTransformers: (program) => ({
      before: [instrumentReactComponentsTransform(program)]
    })
  }
  ...
};