This commit is drafted by a codemod. On modern targets, most plugins in preset-env are not actually enabled. However, when Babel is loading available-plugins, these plugins are still imported. This PR improves loading speed by lazy loading all the available plugins. They are now loaded only when getPlugin is called.

The cost of resolving many small files and their node_modules is tremendous: In the benchmark case, loading unused plugins costs 663ms. In other words, this PR improving loading preset-env from 1.17s to 477ms when compiling against Node.js 15.

Benchmark setup:

Create a babel.config.json with only targets:

{ "targets": { "node": 15 } }

Run V8 CPU profiler separately on Babel repo

// compiles `./packages/babel-preset-env/src/available-plugins.js` with `preset-env` in node_modules
node --predictable --cpu-prof ./node_modules/.bin/babel --config-file ./babel.config.json --presets @babel/preset-env -- ./packages/babel-preset-env/src/available-plugins.js

// compiles `./packages/babel-preset-env/src/available-plugins.js` with `preset-env` in this PR
node --predictable --cpu-prof ./node_modules/.bin/babel --config-file ./babel.config.json --presets ./packages/babel-preset-env -- ./packages/babel-preset-env/src/available-plugins.js

Load the CPU profile in Chrome DevTools. Check the time of the second LoadFullConfig call

Before:

After: