Disable typescript compiling when using NodeNext and --experimental-strip-types

[damianobarbati]

Clear and concise description of the problem

NodeJS recently introduced the new --experimental-strip-types and --experimental-transform-types flags, allowing to .ts files without the need to transpile anything (types are just replaced with 1 empty space).

Full repro here: https://github.com/damianobarbati/ts-repro/

Is it possible to give the developer the option to opt-out of the build-in typescript transpiling when running vitest?
I see unconsistent behaviours arising with imports (probably due to esnext/tsx way of handling cjs).

Suggested solution

Give a flag to opt-out of transpiling.

Alternative

No response

Additional context

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[hi-ogawa]

This feature is probably close to #3995 in the spirit. If having an genuine and more strict node behavior is critical, we have to recommend node test runner for now.

I see unconsistent behaviours arising with imports (probably due to esnext/tsx way of handling cjs).

This is more of resolution difference than transpilation and that's probably a harder part for Vite/Vitest to not intervene.

You can technically disable esbuild transpilation by esbuild: false https://vite.dev/config/shared-options.html#esbuild, but that's not enough since internally Vite expects transpiled js, so it would simply breaks.

[sheremet-va]

Vite is what makes Vitest - Vitest, so the user code will always be processed by Vite. If you wish to support TS in external packages, you can pass down --experimental-strip-types in execArgv: https://vitest.dev/config/#pooloptions-forks-execargv