fix(transform): strip TypeScript declare class fields before class-features plugins run#41624
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…atures plugins run Babel merges plugins and presets into a single traversal, always running plain plugins before presets regardless of list order. Our TypeScript stripping is applied via @babel/preset-typescript (a preset), so the class-features plugins (decorators/class-properties/private-methods) ran before it and choked on not-yet-stripped `declare` class fields. Reordering @babel/preset-typescript into the plugins list fixes that crash, but breaks the relative ordering between TypeScript constructor-parameter- property assignments and class field initializers (a real regression caught by the existing "should be able to access |this| inside class properties" test), since both rely on unshifting into the constructor and the insertion order flips. Instead, add a small dedicated plugin that only strips `declare` class fields, and run it before the class-features plugins, leaving the rest of the pipeline (and its ordering) unchanged. Fixes: microsoft#38586
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Cover the declare-vs-initializer field ordering (issue microsoft#21794) so the test guards against a preset-reordering regression, and simplify the explanatory comment in babelBundle. Fixes: microsoft#38586
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Test results for "MCP"1 failed 7708 passed, 1235 skipped Merge workflow run. |
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Test results for "tests 1"7 flaky49497 passed, 1164 skipped Merge workflow run. |
dgozman
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Jul 7, 2026
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Looks good, thank you for the PR!
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Fixes #38586