fix(transformer/typescript): rewrite extensions in dynamic import() expressions

[sverrejoh]

Closes #20120

rewriteImportExtensions was not handling dynamic import() expressions, only static import/export declarations. TypeScript's rewriteRelativeImportExtensions handles both (via visitImportOrRequireCall in the ESNext module transformer).

The fix adds enter_import_expression visitors at three levels of the transformer dispatch chain. When the import() source is a string literal, it is rewritten the same way as static imports. Non-literal sources (e.g., import(variable)) are left unchanged.

Test fixtures added for both "rewrite" and "remove" modes covering dynamic imports.

Disclosure: AI-assisted (Claude). All changes reviewed and tested by the contributor.

[Copilot]

Pull request overview

This PR fixes TypeScript’s rewriteImportExtensions transformer option to also rewrite file extensions inside dynamic import() expressions (when the import source is a literal), matching TypeScript’s behavior more closely and addressing #20120.

Changes:

• Add enter_import_expression traversal hooks through the transformer dispatch chain so dynamic import() sources can be rewritten.
• Extend the TypeScript rewrite-extensions visitor to rewrite ImportExpression string-literal sources.
• Add/extend conformance fixtures for both "rewrite" and "remove" modes covering dynamic imports.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tasks/transform_conformance/tests/babel-preset-typescript/test/fixtures/rewriteImportExtensions/input.ts	New fixture input covering static + dynamic import extension rewriting cases.
tasks/transform_conformance/tests/babel-preset-typescript/test/fixtures/rewriteImportExtensions/output.js	New expected output asserting dynamic import() literals are rewritten in "rewrite" mode.
tasks/transform_conformance/tests/babel-preset-typescript/test/fixtures/rewriteImportExtensions/options.json	New fixture options enabling rewriteImportExtensions: "rewrite".
tasks/transform_conformance/tests/babel-preset-typescript/test/fixtures/removeImportExtensions/input.ts	Extend existing fixture input to include dynamic imports for "remove" mode.
tasks/transform_conformance/tests/babel-preset-typescript/test/fixtures/removeImportExtensions/output.js	Extend expected output to assert dynamic import() literals are rewritten in "remove" mode.
crates/oxc_transformer/src/typescript/rewrite_extensions.rs	Implement rewriting for ImportExpression when the source is a string literal.
crates/oxc_transformer/src/typescript/mod.rs	Forward enter_import_expression to the rewrite-extensions sub-transform when enabled.
crates/oxc_transformer/src/lib.rs	Forward enter_import_expression from the top-level transformer into the TypeScript preset.

[Dunqing]

looks good!

[codspeed-hq]

Merging this PR will not alter performance

✅ 40 untouched benchmarks
⏩ 16 skipped benchmarks¹

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_{Comparing sverrejoh:fix/rewrite-extensions-dynamic-import (731aff4) with main (a1031cb)²}

Footnotes

1. 16 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. ↩

2. No successful run was found on main (fe3b32e) during the generation of this report, so a1031cb was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[sverrejoh]

looks good!

I can address the template string concern from copilot above. Noticed that TypeScript also supports this.

[sverrejoh]

@Dunqing I can revert the import bare template change hand handle that in a followup, if you think that's cleaner.

TypeScript and babel supports this in the later versons, but they also now support falling back to a runtime helper for importing substitution template strings via a runtime helper. I could tackle that in a followup too.

[Dunqing]

Great