fix(pluginContainer): drop previous sourcesContent

[sun0day]

Description

• refs fix(sourcemap): preserve original sourcesContent #13662
• discuss https://discord.com/channels/804011606160703521/1126017686166585365

Additional context

---

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[patak-dev]

/ecosystem-ci run

[vite-ecosystem-ci]

📝 Ran ecosystem CI: Open

suite	result
analogjs	✅ success
astro	✅ success
histoire	❌ failure
iles	❌ failure
ladle	✅ success
laravel	✅ success
marko	✅ success
nuxt	✅ success
nx	✅ success
previewjs	✅ success
qwik	✅ success
rakkas	✅ success
sveltekit	✅ success
unocss	❌ failure
vite-plugin-pwa	✅ success
vite-plugin-ssr	✅ success
vite-plugin-react	✅ success
vite-plugin-react-pages	✅ success
vite-plugin-react-swc	✅ success
vite-plugin-svelte	✅ success
vite-plugin-vue	✅ success
vite-setup-catalogue	✅ success
vitepress	✅ success
vitest	✅ success

[patak-dev]

Ecosystem CI is good after this PR. I think we should merge to avoid reverting #13662. If we have regressions reported we can still revert and patch it after the 4.4 release.

[sapphi-red]

It seems Vite was using merge-source-map in past and that package didn't handle sourcesContent field correctly and this line was a workaround for it.

vite/packages/vite/src/node/server/pluginContainer.ts

Lines 339 to 345 in a5412f8

	// merge-source-map will overwrite original sources if newMap also has
	// sourcesContent
	// @ts-ignore
	combinedMap = merge(combinedMap, {
	...(m as SourceMap),
	sourcesContent: combinedMap.sourcesContent
	})

Since we now use @ampproject/remapping, I think removing this line makes sense.