fix: missing styles with build watch (#3742)

[janispritzkau]

Description

Fixes issue #3742 by preventing the styles cache from being reset in the vite:css-post plugin on buildStart. This is necessary because already built styles will not be included in subsequent builds, since the function transform will not be called again (where the styles are cached).

Additional context

Maybe there are better ways to solve this without having to cache everything forever.

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the Commit Convention.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

[janispritzkau]

I overlooked the PR that already existed. #3747

[janispritzkau]

Apart from that, mine contains the hasEmitted fix, which fixes a slightly different problem.

I think it's this one: #3566

[patak-dev]

Thanks for the PR @janispritzkau, let's first merge #3747 that was already reviewed, and we can see then if something is missing. In the meantime, if you want to help test it, and maybe add a test case to your PR that is not going to pass with #3747 that would be good.

[patak-dev]

Ok, I saw now that there were enough approvals to merge it. Could you merge main against this PR and add a failing test for the bits that are not covered there? Thanks!

[antfu]

Tested locally and confirmed the fix. Thanks!

[j]

@antfu @patak-dev I'm not getting refreshes working in lib mode...

[patak-dev]

@j please create a new issue with a minimal reproduction. Thanks!