fix(transformer/legacy-decorator): correct generating metadata for getter/setter methods

[Dunqing]

• Fixes: transformer: miscalculates design:returntype for getter properties #14493

Getter and setter methods should not have design:returntype metadata according to TypeScript's emitDecoratorMetadata behavior. They should only have design:type and design:paramtypes.

And design:type is different for the getter and setter:

Getter: design:type is the same as the return type of method.
Setter: design:type is the same as the type of the first parameter of the method

[Dunqing]

• fix(transformer/legacy-decorator): correct generating metadata for getter/setter methods #14495 👈 (View in Graphite)
• main

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[codspeed-hq]

CodSpeed Performance Report

Merging #14495 will not alter performance

_{Comparing 10-11-fix_transformer_skip_design_returntype_metadata_for_getter_setter_methods (eae13e6) with main (bec7a7d)}

Summary

✅ 33 untouched
⏩ 4 skipped¹

Footnotes

1. 4 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[Copilot]

Pull Request Overview

This PR fixes the TypeScript decorator metadata generation for getter and setter methods to match TypeScript's emitDecoratorMetadata behavior. Getter and setter methods should not include design:returntype metadata, only design:type and design:paramtypes.

• Fixed metadata generation to exclude design:returntype for getter/setter methods
• Updated the method metadata stack to use optional expressions to handle varying metadata counts
• Added test coverage for getter/setter method metadata behavior

Reviewed Changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
crates/oxc_transformer/src/decorator/legacy/metadata.rs	Modified metadata generation logic to conditionally include return type metadata and updated data structures to support optional expressions
crates/oxc_transformer/src/decorator/legacy/mod.rs	Updated metadata processing to handle optional expressions with flattening
tasks/transform_conformance/tests/legacy-decorators/test/fixtures/oxc/metadata/getter-setter-method/input.ts	Added test input with decorated getter, setter, and regular method
tasks/transform_conformance/tests/legacy-decorators/test/fixtures/oxc/metadata/getter-setter-method/output.js	Expected output showing correct metadata generation (no returntype for getter/setter)
tasks/transform_conformance/snapshots/oxc.snap.md	Updated test results to reflect the new passing test

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[Dunqing]

Merge activity

• Oct 22, 8:56 AM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Oct 22, 8:56 AM UTC: Dunqing added this pull request to the Graphite merge queue.
• Oct 22, 9:03 AM UTC: Merged by the Graphite merge queue.