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perf(css): only run postcss when needed #19061

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perf(css): only run postcss when needed #19061

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643d152
perf: only run postcss when needed
sapphi-red Dec 24, 2024
4c777ac
chore: merge main
sapphi-red Dec 25, 2024
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63 changes: 34 additions & 29 deletions packages/vite/src/node/plugins/css.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1271,7 +1271,6 @@ async function compileCSS(
): Promise<{
code: string
map?: SourceMapInput
ast?: PostCSS.Result
modules?: Record<string, string>
deps?: Set<string>
}> {
Expand All @@ -1280,51 +1279,49 @@ async function compileCSS(
return compileLightningCSS(id, code, environment, urlReplacer)
}

const lang = CSS_LANGS_RE.exec(id)?.[1] as CssLang | undefined
const deps = new Set<string>()

// pre-processors: sass etc.
let preprocessorMap: ExistingRawSourceMap | undefined
if (isPreProcessor(lang)) {
const preprocessorResult = await compileCSSPreprocessors(
environment,
id,
lang,
code,
workerController,
)
code = preprocessorResult.code
preprocessorMap = preprocessorResult.map
preprocessorResult.deps?.forEach((dep) => deps.add(dep))
}

const { modules: modulesOptions, devSourcemap } = config.css
const isModule = modulesOptions !== false && cssModuleRE.test(id)
// although at serve time it can work without processing, we do need to
// crawl them in order to register watch dependencies.
const needInlineImport = code.includes('@import')
const hasUrl = cssUrlRE.test(code) || cssImageSetRE.test(code)
const lang = CSS_LANGS_RE.exec(id)?.[1] as CssLang | undefined
const postcssConfig = await resolvePostcssConfig(
environment.getTopLevelConfig(),
)

// 1. plain css that needs no processing
// postcss processing is not needed
if (
lang === 'css' &&
lang !== 'sss' &&
!postcssConfig &&
!isModule &&
!needInlineImport &&
!hasUrl
) {
return { code, map: null }
return { code, map: preprocessorMap ?? null, deps }
}
Comment on lines +1311 to 1320
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With this PR, If the preprocessor removed all @import, we might be able to return at this line. (previously postcss was run)


let modules: Record<string, string> | undefined
const deps = new Set<string>()

// 2. pre-processors: sass etc.
let preprocessorMap: ExistingRawSourceMap | undefined
if (isPreProcessor(lang)) {
const preprocessorResult = await compileCSSPreprocessors(
environment,
id,
lang,
code,
workerController,
)
code = preprocessorResult.code
preprocessorMap = preprocessorResult.map
preprocessorResult.deps?.forEach((dep) => deps.add(dep))
}

// 3. postcss
// postcss
const atImportResolvers = getAtImportResolvers(
environment.getTopLevelConfig(),
)
const postcssOptions = postcssConfig?.options ?? {}
const postcssPlugins = postcssConfig?.plugins.slice() ?? []

if (needInlineImport) {
Expand Down Expand Up @@ -1386,7 +1383,13 @@ async function compileCSS(
)
}

if (urlReplacer) {
if (
urlReplacer &&
// if there's an @import, we need to add this plugin
// regradless of whether it contains url() or image-set(),
// because we don't know the content referenced by @import
(needInlineImport || cssUrlRE.test(code) || cssImageSetRE.test(code))
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Suggested change
(needInlineImport || cssUrlRE.test(code) || cssImageSetRE.test(code))
(needInlineImport || hasUrl)

It seems like we can reuse the variable here

) {
postcssPlugins.push(
UrlRewritePostcssPlugin({
replacer: urlReplacer,
Comment on lines +1387 to 1396
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UrlRewritePostcssPlugin was always pushed, so postcss was ran always.

Expand All @@ -1395,6 +1398,8 @@ async function compileCSS(
)
}

let modules: Record<string, string> | undefined

if (isModule) {
postcssPlugins.unshift(
(await importPostcssModules()).default({
Expand Down Expand Up @@ -1428,7 +1433,7 @@ async function compileCSS(
)
}

if (!postcssPlugins.length) {
if (lang !== 'sss' && !postcssPlugins.length) {
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This lang !== 'sss' was not needed because !postcssPlugins.length was always false.

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I'm a bit confused about this part. Isn't sugarss support added as a postcss plugin, so postcssPlugins.length should be at least one?

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It's because sugarss is a parser and not a plugin.

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

Line 1447 in da0caf5

parser: lang === 'sss' ? loadSss(config.root) : postcssOptions.parser,

Now that you mentioned about it, I think we should change this condition to lang !== 'sss' && !postcssOptions.parser && !postcssPlugins.length.

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Ah I didn't know it's a parser. Yeah I think checking for parser seems better too.

return {
code,
map: preprocessorMap,
Expand All @@ -1440,6 +1445,8 @@ async function compileCSS(
try {
const source = removeDirectQuery(id)
const postcss = await importPostcss()
const postcssOptions = postcssConfig?.options ?? {}

// postcss is an unbundled dep and should be lazy imported
postcssResult = await postcss.default(postcssPlugins).process(code, {
...postcssOptions,
Expand Down Expand Up @@ -1509,7 +1516,6 @@ async function compileCSS(

if (!devSourcemap) {
return {
ast: postcssResult,
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ast was not used anywhere.

code: postcssResult.css,
map: { mappings: '' },
modules,
Expand All @@ -1527,7 +1533,6 @@ async function compileCSS(
)

return {
ast: postcssResult,
code: postcssResult.css,
map: combineSourcemapsIfExists(cleanUrl(id), postcssMap, preprocessorMap),
modules,
Expand Down
8 changes: 4 additions & 4 deletions playground/css-sourcemap/__tests__/css-sourcemap.spec.ts
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The sourcemaps changed because postcss does not run on these files anymore.

Original file line number Diff line number Diff line change
Expand Up @@ -138,8 +138,8 @@ describe.runIf(isServe)('serve', () => {
const map = extractSourcemap(css)
expect(formatSourcemapForSnapshot(map)).toMatchInlineSnapshot(`
{
"ignoreList": [],
"mappings": "AAGE;EACE,UCJM",
"mappings": "AAGE;EACE,OCJM",
"sourceRoot": "",
"sources": [
"/root/imported.sass",
"/root/imported-nested.sass",
Expand Down Expand Up @@ -186,7 +186,7 @@ describe.runIf(isServe)('serve', () => {
expect(formatSourcemapForSnapshot(map)).toMatchInlineSnapshot(`
{
"ignoreList": [],
"mappings": "AACE;EACE",
"mappings": "AACE,SAAC;EACC",
"sources": [
"/root/imported.less",
],
Expand All @@ -209,7 +209,7 @@ describe.runIf(isServe)('serve', () => {
expect(formatSourcemapForSnapshot(map)).toMatchInlineSnapshot(`
{
"ignoreList": [],
"mappings": "AACE;EACE,cAAM",
"mappings": "AACE;EACE,OAAM,QAAN",
"sources": [
"/root/imported.styl",
],
Expand Down
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