fix: ensure new CSS modules cache at build start

[patak-dev]

Description

This is related to #3512. I don't have a test for it, but looks like not resetting the cache can lead to stale CSS modules caches so it is better to have a clean cache at build start following the same pattern as with the assets plugin.

For a theoric reproduction of the stale cache, when rebuilding in watch mode, if there was an id that generated modules as undefined after being properly defined in the previous build, then it will not reset the cached id here

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

Line 174 in 5979d0e

if (modules) {

So, the old cached value will remain in the map and could be used in the vite:css-post plugin here

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

Line 240 in 5979d0e

modules && dataToEsm(modules, { namedExports: true, preferConst: true })

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[underfin]

Maybe here also need reset cache for css.

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

Line 227 in 5979d0e

const outputToExtractedCSSMap = new Map<NormalizedOutputOptions, string>()

[patak-dev]

Updated the PR to also generate new caches at build start for the vite:css-post plugin as proposed by @underfin