Improve output of super()

[liuxingbaoyu]

Q	A
Fixed Issues?	Fixes #1, Fixes #2
Patch: Bug Fix?
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

This is a small change, and if we can merge it before the next release, we won't need to add a new-version-checklist. :) (Some of my other PRs are a bit troublesome to rebase)

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/56080/

[JLHwung]

@JoshuaKGoldberg If we set parserOptions.ecmaVersion to 5, will typescript-eslint respect the ecmaVersion and automatically turn off this rule?

[JoshuaKGoldberg]

Interesting idea! No, rules in the preset configs won't be configured differently based on your parserOptions. I don't believe ESLint configs can be dynamic in this way. At least legacy ones aren't, and we haven't added official support for flat configs yet.

[JLHwung]

@JoshuaKGoldberg Thank you! I think this is not a very common use case, since most TS projects will use tsc to transpile ts sources anyway.

@liuxingbaoyu Can we set parserOptions.ecmaVersion to 5 for helpers? So the linter should throw if there are non-ES5 codes.

[liuxingbaoyu]

Parsing error: ImportDeclaration should appear when the mode is ES6 and in the module context.
I tried it and it didn't work.
Our current ts source actually has some es6 syntax such as trailingComma handled by terser which I think is fine.
I have now unified js with ts and explicitly specified terser as es5.

[liuxingbaoyu]

Thanks for the tag! Now that we have released v7.23.7, I removed it as it should be included in the next release no later than later. :)

[liuxingbaoyu]

Luckily github fixed their CI issue, this PR has test262 failure, I will fix it.

[nicolo-ribaudo]

When compiling this code:

class A extends B {
  constructor(arg1, arg2, arg3) {
    super(arg1, arg2);
    this.arg3 = arg3;
  }
}

targeting IE11, and manually replacing helper names with one-char variables when minifing, the output size is:

	Before this PR	After this PR
Size	315 bytes	123 bytes
Minified size	287 bytes	111 bytes

The old code is slightly faster in some very old browsers when compiling implicit constructors, because we pass arguments to .apply that had optimized handling. However, now the "pass arguments to another function" deopt doesn't exist anymore.

[liuxingbaoyu]

Now we avoid a function call/new closure, hoping that this can offset performance changes. : :)

[nicolo-ribaudo]

I'll avoid the new-version-checklist change, hoping that the next release will be a patch :)

[liuxingbaoyu]

Yeah, due to the regression fix #16199, we are enough to release a patch version. : :)

[steverep]

Hi, could this change have caused a regression in output size? Home Assistant is seeing a hefty 4% bundle size increase from 7.23.7 to 7.23.8 (home-assistant/frontend#19368).

Looking at the release notes, this PR seems like the only viable culprit.

[steverep]

Took a deeper look and it seems the bundle is no longer using @babel/runtime/helpers/esm/createSuper.js, so a significant portion of our transpiled modules went up by those ~800 bytes.

[liuxingbaoyu]

The purpose of this PR is to reduce the output size, but it may cause the size to increase when users use the new @babel/plugin-transform-classes and the old @babel/helper.

I noticed home-assistant/frontend@349c6cf (#19368), does this solve the problem?

[steverep]

Yes, I noticed @babel/helpers was still locked at 7.23.7 and bumped it. That did seem to fix the problem.