Review experimental options for Vite 3

[bluwy]

Clear and concise description of the problem

For Vite 3, we can review some experimental options to be stable APIs.

Suggested solution

Things to review:

• server.preTransformRequests (feat: option to disable pre-transform #6309)
• server.fs.deny (feat: server.fs.deny support #5378)
• preview() to create a preview server (feat: expose preview method #5014)
• ssrTransform() (feat: expose ssrTransform to server #5983)

Newer experimental options:

• css.devSourcemap (feat(css): css.devSourcemap option #7471)
• optimizeDeps.extensions (feat: optimize custom extensions #6801)

Alternative

No response

Additional context

Note:

For preview(), SvelteKit hasn't been using it as otherwise mentioned in the PR. They work differently that SvelteKit implements its own preview server.

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.

[patak-dev]

I think all the listed features under Things to review could be out of experimental. Maybe we could do individual PRs for each of them and add some projects from the ecosystem that are using them as reference?

css.devSourcemap we could delay the decision until have more users testing the feature, but leaning towards leaving it as experimental too.
optimizeDeps.extensions should probably stay as previously discussed

[bluwy]

👍 Yeah I think things to review has been pretty stable too. I was thinking we can do one PR for all of them perhaps since it's a matter of removing the @experimental comment only. Will open a PR with some usage info soon.