feat(transformer): class properties transform

[overlookmotel]

Add class properties transform.

Implementation is incomplete. Notable missing parts:

• Scopes are not updated where property initializers move from class body into class constructor / _super function.
• Does not handle binding shadowing problems when property initializers move from class body into class constructor.
• this and references to class name in static property initializers need to be transformed to point to a temp var.
• Not all usages of private properties are supported (see below).
• Code which is moved to outside of class body is not transformed by other transforms for class declarations (works OK for class expressions). This includes static property initializers, static blocks, and computed property/method keys.
• Only basic checks for whether computed property/method keys may have side effects.
• Numerous other small issues noted in TODO comments through the code.

Private properties

Currently does not handle the following usages of private properties:

class Class {
  #prop;
  static #static;
  
  method() {
    object?.#prop;
    object?.#prop();
    [object.#prop] = [1];
    ({x: object.#prop} = {x: 1});
    object.#prop`xyz`;
    
    object?.#static;
    object?.#static();
    [object.#static] = [1];
    ({x: object.#static} = {x: 1});
    object.#static`xyz`;
  }
}

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[overlookmotel]

• feat(transformer): class properties transform #7011 👈 (View in Graphite)
• test(transformer): script to amend Babel fixtures #7122
• feat(traverse): add methods to BoundIdentifier + MaybeBoundIdentifier to create SimpleAssignmentTargets #7418
• docs(traverse): fix docs for BoundIdentifier + MaybeBoundIdentifier #7417
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[codspeed-hq]

CodSpeed Performance Report

Merging #7011 will degrade performances by 19.21%

_{Comparing 10-29-feat_transformer_class_properties_transform (9778298) with main (0b9da38)}

Summary

❌ 3 regressions
✅ 27 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	10-29-feat_transformer_class_properties_transform	Change
❌	transformer[antd.js]	49.6 ms	53.9 ms	-7.98%
❌	transformer[checker.ts]	20.8 ms	23.1 ms	-9.97%
❌	transformer[pdf.mjs]	7.8 ms	9.6 ms	-19.21%

[Boshen]

Too much fixtures committed to this repo, let me think about #4048

[overlookmotel]

Yes, I hope there's a better solution. I just wanted some working tests while I'm building the transform.

[overlookmotel]

@Boshen @Dunqing As noted above, this transform is incomplete. But I think it's in a fit state to merge at this point so we can iterate on it.

Note: Transform is not enabled by default, so I think monitor-oxc won't fail if we merge this.

[Boshen]

Merge activity

• Nov 25, 5:23 AM EST: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Nov 25, 5:23 AM EST: A user added this pull request to the Graphite merge queue.
• Nov 25, 5:30 AM EST: A user merged this pull request with the Graphite merge queue.