fix(css): file or contents missing error in build watch (#3742)

[javastation]

Description

Fix #3742, styles will be incomplete，because styles is initialized in buildStart.

vite/packages/vite/src/node/plugins/css.ts

Line 290 in 5979d0e

if (styles.has(id)) {

In asset.ts, assetHashToFilenameMap initialization in buildStart causes getAssetFilename called in css.ts to return undefined.

vite/packages/vite/src/node/plugins/css.ts

Line 314 in 5979d0e

const filename = getAssetFilename(fileHash, config) + postfix

I add another variable emittedHashesSet to determine whether to emit a file.

Additional context

---

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• 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.

[Shinigami92]

Could you add tests that will fail when your fix is not applied?

[javastation]

Ok, you can read my repo in #3742 about styles, I will create a new branch to reproduce the problem of returning undefined.

[javastation]

This is repo https://github.com/javastation/vite/tree/bug

1. clone https://github.com/javastation/vite/tree/bug and checkout bug
2. run yarn and yarn build-vite
3. cd ./vite/packages/playground/assets
4. run yarn watch
5. make some changes to index.html, you will find undefined in index.*.cssin dist
6. if you change icons.css, emitFile will trigger multiple times

[Shinigami92]

What I meant was a test in our test-suite, so e.g. a unit test or integration test in one of the playgrounds. This way it will always checked when someone create a PR.
Your reproduction repo will currently only be checked once and then pass away.
So I would like to see tests to prevent e.g. regression in the future.

[javastation]

Ok, I got it wrong before.

[patak-dev]

This is a great first PR to the project @javastation. Thanks a lot for also taking the time to improve the test suite.

Not for this PR, but if you would like to do so, it would be great if you could do a review of other plugin caches and how they interact with build watch. I sent a few PRs trying to fix build watch a few versions ago ( #3537, #3516, #3530, #3512 ), but I didn't take into account the internal rollup cache that prevents unmodified files to go through the hooks pipeline in each build. There is also another cache in the build-html plugin (see #3535) that I couldn't modify and it may be related to the issue you found. Thanks again, I hope we keep seeing you around in the project 👍🏼

[javastation]

I also noticed the html-plugin yesterday, some static assets in html will emit multiple times in build watch, cache collection is necessary, I will also try to do something for the project.