DEVELOPMENT.md

esfixup Development

Structure of this Package

TODO

Developing a Babel Plugin

Most of the transforms we have are actually Babel Plugins, so docs you find on how to write those, and the API to use, should work fine. Here are some good references:

• Babel Plugin Handbook - a good introduction
• @babel/types API - what's available to you in the t variable in most plugins
• AST Explorer - an interactive tool to help write plugin transformers (HIGHLY recommended)

Manually Testing a Single Plugin

Most of the files that live in a directory named transforms/ are actually valid Babel plugins. If their modules.exports is a function which takes { types: t } and returns an object like { visitor: { ... } }, then that's almost certainly one. In that case, you can test them directly by running the babel CLI itself.

For example if we want to try out the global-url js sub-transform:

$ cat ~/foo.js
'use strict';

const { URL } = require('url');

const url = new URL();

$ npx babel \
  --no-babelrc \
  --plugins ./lib/transforms/js/transforms/global-url.js \
  < ~/foo.js
'use strict';

const url = new URL();