v2.0.0

   🚨 Breaking Changes

• lib-instrument: Replace babel with rolldown + magic-string  -  by @AriPerkkio in #28 (fdd34)

@vitest/istanbul-lib-instrument no longer uses Babel. Code is parsed with OXC (via rolldown) and coverage counters are inserted into the original code with magic-string. The coverage maps produced are the same as before. (#28)

• rolldown is now a dependency (^1.0.0). Vite 8 and Vitest 5 already depend on it.
• Removed programVisitor (and the VisitorOptions / VisitorExitResult types). The Babel-plugin API has no replacement.
• Removed the parserPlugins and generatorOpts options. JSX, decorators, import attributes and other modern syntax parse without plugins. TypeScript is not parsed; transpile it before instrumenting.
• compact, preserveComments and debug are deprecated and have no effect. The original code, including its formatting and comments, is kept as-is.
• Instrumented output looks different. The original formatting, comments and line numbers are kept, and the coverage header sits on the first line (after any hashbang or "use strict").
• readInitialCoverage() accepts a code string or an ESTree Program (from OXC/rolldown) instead of a Babel AST. Code instrumented by previous versions is still read correctly.
• Source maps referenced by sourceMappingURL comments are no longer loaded automatically. Pass inputSourceMap to instrumentSync() explicitly.
• Parse errors are OXC SyntaxErrors, with different messages. Some strict-mode errors Babel reported, such as with in ES modules, are no longer raised.

   🚀 Features

• lib-instrument: Add combineSourceMaps option to support vitest-dev/vitest#9040 better  -  by @AriPerkkio in #29

🏎 Performance

Instrumenting with @vitest/istanbul-lib-instrument 1.0.2 vs 2.0.0. TypeScript inputs are first transformed to JavaScript with a source map, the same way Vite does before Vitest's coverage plugin runs, and instrumented with the options of @vitest/coverage-istanbul.

Usage via @vitest/coverage-istanbul.
Includes speed-up from combineSourceMaps: false (see vitest-dev/vitest#9040):

Input	Vitest 5.x + 1.0.2	Vitest + 2.0.0	Speedup
TypeScript's checker.ts	4,328 ms	501 ms	8.6×
Vitest repository, 479 files	3,727 ms	376 ms	9.9×

Plain library usage:

Input	Size (JS)	1.0.2	2.0.0	Speedup	Memory (RSS) 1.0.2 → 2.0.0
TypeScript's checker.ts, 1 file	2.4 MB, 48k lines	2,198 ms	567 ms	3.9×	2.7 GB → 0.8 GB
Vitest repository, 479 source files	1.9 MB, 56k lines	1,913 ms	443 ms	4.3×	313 MB → 211 MB

Coverage results are identical between the versions: the same statements, functions and branches (39,720 for checker.ts, 39,985 for the Vitest repository).

_{Apple M2, 16 GB, Node.js 22.22.0. Each number is the median of 3 separate processes with 5 iterations each, after a warmup run. Time covers instrumentSync() only, not parsing the TypeScript source.}

📦 Dependency reduction

@babel/core and @babel/parser are removed from the dependency tree. @vitest/istanbul-lib-instrument now depends on @istanbuljs/schema, @jridgewell/remapping, @jridgewell/trace-mapping, magic-string and rolldown. Most of these are transitive dependencies in Vitest.

    View changes on GitHub