refactor: replace regexp-tree by regexpu

[JLHwung]

Q	A
Fixed Issues?	Standardize on regexpu
Patch: Bug Fix?
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

This is our first step to standardize regexp transforms on regexpu. It helps reduce the package size and pave the way for an integral approach to treat unicode regex.

Currently the test failure is due to an upstream issue.

---

Edit by @nicolo-ribaudo

Depends on:

• Only capturing groups update the group index mathiasbynens/regexpu-core#28
• Optimize compilation of /./ when "u" is not enabled mathiasbynens/regexpu-core#29
• chore: bump regexpu-core to version 4.6.0 #10439

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/11571/

[buildsize]

File name	Previous Size	New Size	Change
babel-preset-env.js	2.43 MB	2.73 MB	313.86 KB (13%)
babel-preset-env.min.js	1.4 MB	1.65 MB	256.47 KB (18%)
babel.js	2.95 MB	2.95 MB	9 bytes (0%)
babel.min.js	1.63 MB	1.63 MB	9 bytes (0%)

[JLHwung]

The size change of @babel/preset-env-standalone comes from the fact that @babel/plugin-transform-named-capturing-groups is not included in https://github.com/babel/babel/blob/master/packages/babel-standalone/scripts/pluginConfig.json, therefore, it will instead be bundled into @babel/preset-env-standalone instead of @babel/standalone.

Looking into the pluginConfig.json, it seems that even while Stage 0 proposal (function-bind) is included in pluginConfig, a Stage 4 proposal (named-capturing-groups) is not included. I believe it is a bug and would propose to move all notIncludedPlugins

babel/packages/babel-preset-env-standalone/src/available-plugins.js

Lines 3 to 8 in 256fa5a

	const notIncludedPlugins = {
	"transform-named-capturing-groups-regex": require("@babel/plugin-transform-named-capturing-groups-regex"),
	"transform-new-target": require("@babel/plugin-transform-new-target"),
	"proposal-json-strings": require("@babel/plugin-proposal-json-strings"),
	"proposal-dynamic-import": require("@babel/plugin-proposal-dynamic-import"),
	};

into pluginsConfig.json. We expect a slight size increase of babel.js and decrease of babel-preset-env.js. In all the total size will be reduced since we are not including regexp-tree.

Side note: we may need specify the peerDependencies of @babel/preset-env-standalone to be @babel/standalone.

[nicolo-ribaudo]

IIRC, notIncludedPlugins includes all the plugin from preset-env which are not part of the es* or stage-* presets.

Ideally, @babel/standalone should be as small as possible and all the plugins should only be in @babel/preset-env-standalone, but for legacy reasons we can't just move them.
By doing so, users can update preset-env-standalone without having to udpate @babel/standalone when a new plugin is added.
Unless there is a webpack hack to load regexpu-core from the @babel/standalone bundle in @babel/preset-env-standalone, I don't think that there is anything that we can do to remove that duplicated dependency.

[JLHwung]

Thank you for the explainers!

Unless there is a webpack hack to load regexpu-core from the @babel/standalone bundle in @babel/preset-env-standalone, I don't think that there is anything that we can do to remove that duplicated dependency.

The webpack dll is supposed to offer a runtime require-able libraries for webpack application. But from my previous experience I would rather stay away from it especially when we required cross-version compatibility between babel/standalone and preset-env-standalone.

I guess we have to accept the size change. But maybe we can deprecate plugin usage in babel-standalone? So we can move plugins to preset-env on v8 (not the JS engine).