fix(rsc): include bundled server CSS when cssCodeSplit is false

packages/plugin-rsc/e2e/css-code-split.test.ts

@@ -0,0 +1,91 @@
+import fs from 'node:fs'
+import path from 'node:path'
+import { expect, test } from '@playwright/test'
+import { setupInlineFixture, useFixture } from './fixture'
+import { waitForHydration } from './helper'
+import { defineStarterTest } from './starter'
+
+// When `build.cssCodeSplit: false`, Vite emits a single consolidated CSS
+// bundle asset and no `importedCss` metadata on chunks. The rsc plugin must
+// still copy the rsc environment's CSS asset into the client output and
+// reference it from server-component resources, otherwise RSC-only CSS
+// (e.g. from a server component module) goes missing from the client build.
+
+test.describe('cssCodeSplit-false', () => {
+  const root = 'examples/e2e/temp/cssCodeSplit-false'
+
+  test.beforeAll(async () => {
+    await setupInlineFixture({
+      src: 'examples/starter',
+      dest: root,
+      files: {
+        'vite.config.ts': /* js */ `
+          import rsc from '@vitejs/plugin-rsc'
+          import react from '@vitejs/plugin-react'
+          import { defineConfig } from 'vite'
+
+          export default defineConfig({
+            build: { cssCodeSplit: false },
+            plugins: [
+              react(),
+              rsc({
+                entries: {
+                  client: './src/framework/entry.browser.tsx',
+                  ssr: './src/framework/entry.ssr.tsx',
+                  rsc: './src/framework/entry.rsc.tsx',
+                }
+              }),
+            ],
+          })
+        `,
+        // CSS module imported exclusively by a server component module, so its
+        // styles only reach the client via plugin-rsc's server-resources <link>
+        // path.
+        'src/server-only.module.css': /* css */ `
+          .serverOnly {
+            color: rgb(123, 45, 67);
+          }
+        `,
+        'src/server-only.tsx': /* js */ `
+          import styles from './server-only.module.css'
+          export function ServerOnly() {
+            return <div data-testid="server-only" className={styles.serverOnly}>rsc-css-only</div>
+          }
+        `,
+        'src/root.tsx': {
+          edit: (s) =>
+            s
+              .replace(
+                `import { ClientCounter } from './client.tsx'`,
+                `import { ClientCounter } from './client.tsx'\nimport { ServerOnly } from './server-only.tsx'`,
+              )
+              .replace(`<ClientCounter />`, `<ClientCounter /><ServerOnly />`),
+        },
+      },
+    })
+  })
+
+  test.describe('build', () => {
+    const f = useFixture({ root, mode: 'build' })
+    defineStarterTest(f)
+
+    test('rsc-only css is present in the client output', () => {
+      const dir = path.join(f.root, 'dist/client/assets')
+      const cssFiles = fs.readdirSync(dir).filter((n) => n.endsWith('.css'))
+      const combined = cssFiles
+        .map((n) => fs.readFileSync(path.join(dir, n), 'utf-8'))
+        .join('\n')
+      // minifier may hex-encode; accept either form
+      expect(combined).toMatch(/rgb\(123,\s*45,\s*67\)|#7b2d43/i)
+    })
+
+    test('rsc-only css is applied at runtime', async ({ page }) => {
+      await page.goto(f.url())
+      await waitForHydration(page)
+      await expect(page.getByTestId('server-only')).toHaveCSS(
+        'color',
+        'rgb(123, 45, 67)',
+      )
+    })
+  })
+})

packages/plugin-rsc/src/plugin.ts

@@ -1065,93 +1065,117 @@ export function createRpcClient(params) {
         },
       },
       // client build
-      generateBundle(_options, bundle) {
-        // copy assets from rsc build to client build
-        manager.bundles[this.environment.name] = bundle
-
-        if (this.environment.name === 'client') {
-          const rscBundle = manager.bundles['rsc']!
-          const assets = new Set(
-            Object.values(rscBundle).flatMap((output) =>
-              output.type === 'chunk'
-                ? [
-                    ...(output.viteMetadata?.importedCss ?? []),
-                    ...(output.viteMetadata?.importedAssets ?? []),
-                  ]
-                : [],
-            ),
-          )
-          for (const fileName of assets) {
-            const asset = rscBundle[fileName]
-            assert(asset?.type === 'asset')
-            this.emitFile({
-              type: 'asset',
-              fileName: asset.fileName,
-              source: asset.source,
-            })
-          }
+      generateBundle: {
+        // run after vite's css plugin emits the consolidated stylesheet
+        // (relevant when `build.cssCodeSplit: false`).
+        order: 'post',
+        handler(_options, bundle) {
+          // copy assets from rsc build to client build
+          manager.bundles[this.environment.name] = bundle
 
-          const serverResources: Record<string, AssetDeps> = {}
-          const rscAssetDeps = collectAssetDeps(manager.bundles['rsc']!)
-          for (const [id, meta] of Object.entries(
-            manager.serverResourcesMetaMap,
-          )) {
-            serverResources[meta.key] = assetsURLOfDeps(
-              {
-                js: [],
-                css: rscAssetDeps[id]?.deps.css ?? [],
-              },
-              manager,
+          if (this.environment.name === 'client') {
+            const rscBundle = manager.bundles['rsc']!
+            const assets = new Set(
+              Object.values(rscBundle).flatMap((output) =>
+                output.type === 'chunk'
+                  ? [
+                      ...(output.viteMetadata?.importedCss ?? []),
+                      ...(output.viteMetadata?.importedAssets ?? []),
+                    ]
+                  : [],
+              ),
             )
-          }
-
-          const assetDeps = collectAssetDeps(bundle)
-          let bootstrapScriptContent: string | RuntimeAsset = ''
-
-          const clientReferenceDeps: Record<string, AssetDeps> = {}
-          for (const meta of Object.values(manager.clientReferenceMetaMap)) {
-            const deps: AssetDeps = assetDeps[meta.groupChunkId!]?.deps ?? {
-              js: [],
-              css: [],
+            // when the rsc environment has `cssCodeSplit: false`, Vite emits a
+            // single bundled CSS asset and chunks carry no `importedCss` metadata.
+            // Pick the bundled CSS asset(s) directly so they get copied and
+            // referenced by server resources.
+            const rscCssCodeSplit =
+              manager.config.environments.rsc?.build.cssCodeSplit
+            const rscBundledCssFileNames =
+              rscCssCodeSplit === false
+                ? collectBundledCssAssetFileNames(rscBundle)
+                : []
+            for (const fileName of rscBundledCssFileNames) {
+              assets.add(fileName)
+            }
+            for (const fileName of assets) {
+              const asset = rscBundle[fileName]
+              assert(asset?.type === 'asset')
+              this.emitFile({
+                type: 'asset',
+                fileName: asset.fileName,
+                source: asset.source,
+              })
             }
-            clientReferenceDeps[meta.referenceKey] = assetsURLOfDeps(
-              deps,
-              manager,
-            )
-          }
 
-          // When customClientEntry is enabled, don't require "index" entry
-          // and don't merge entry deps into client references
-          if (!rscPluginOptions.customClientEntry) {
-            const entry = Object.values(assetDeps).find(
-              (v) => v.chunk.name === 'index' && v.chunk.isEntry,
-            )
-            if (!entry) {
-              throw new Error(
-                `[vite-rsc] Client build must have an entry chunk named "index". Use 'customClientEntry' option to disable this requirement.`,
+            const serverResources: Record<string, AssetDeps> = {}
+            const rscAssetDeps = collectAssetDeps(manager.bundles['rsc']!)
+            for (const [id, meta] of Object.entries(
+              manager.serverResourcesMetaMap,
+            )) {
+              const cssDeps = new Set(rscAssetDeps[id]?.deps.css ?? [])
+              if (rscCssCodeSplit === false) {
+                for (const fileName of rscBundledCssFileNames) {
+                  cssDeps.add(fileName)
+                }
+              }
+              serverResources[meta.key] = assetsURLOfDeps(
+                {
+                  js: [],
+                  css: [...cssDeps],
+                },
+                manager,
               )
             }
-            const entryDeps = assetsURLOfDeps(entry.deps, manager)
-            for (const [key, deps] of Object.entries(clientReferenceDeps)) {
-              clientReferenceDeps[key] = mergeAssetDeps(deps, entryDeps)
+
+            const assetDeps = collectAssetDeps(bundle)
+            let bootstrapScriptContent: string | RuntimeAsset = ''
+
+            const clientReferenceDeps: Record<string, AssetDeps> = {}
+            for (const meta of Object.values(manager.clientReferenceMetaMap)) {
+              const deps: AssetDeps = assetDeps[meta.groupChunkId!]?.deps ?? {
+                js: [],
+                css: [],
+              }
+              clientReferenceDeps[meta.referenceKey] = assetsURLOfDeps(
+                deps,
+                manager,
+              )
             }
-            const entryUrl = assetsURL(entry.chunk.fileName, manager)
-            if (typeof entryUrl === 'string') {
-              bootstrapScriptContent = `import(${JSON.stringify(entryUrl)})`
-            } else {
-              bootstrapScriptContent = new RuntimeAsset(
-                `"import(" + JSON.stringify(${entryUrl.runtime}) + ")"`,
+
+            // When customClientEntry is enabled, don't require "index" entry
+            // and don't merge entry deps into client references
+            if (!rscPluginOptions.customClientEntry) {
+              const entry = Object.values(assetDeps).find(
+                (v) => v.chunk.name === 'index' && v.chunk.isEntry,
               )
+              if (!entry) {
+                throw new Error(
+                  `[vite-rsc] Client build must have an entry chunk named "index". Use 'customClientEntry' option to disable this requirement.`,
+                )
+              }
+              const entryDeps = assetsURLOfDeps(entry.deps, manager)
+              for (const [key, deps] of Object.entries(clientReferenceDeps)) {
+                clientReferenceDeps[key] = mergeAssetDeps(deps, entryDeps)
+              }
+              const entryUrl = assetsURL(entry.chunk.fileName, manager)
+              if (typeof entryUrl === 'string') {
+                bootstrapScriptContent = `import(${JSON.stringify(entryUrl)})`
+              } else {
+                bootstrapScriptContent = new RuntimeAsset(
+                  `"import(" + JSON.stringify(${entryUrl.runtime}) + ")"`,
+                )
+              }
             }
-          }
 
-          manager.buildAssetsManifest = {
-            bootstrapScriptContent,
-            clientReferenceDeps,
-            serverResources,
-            cssLinkPrecedence: rscPluginOptions.cssLinkPrecedence,
+            manager.buildAssetsManifest = {
+              bootstrapScriptContent,
+              clientReferenceDeps,
+              serverResources,
+              cssLinkPrecedence: rscPluginOptions.cssLinkPrecedence,
+            }
           }
-        }
+        },
       },
       // non-client builds can load assets manifest as external
       renderChunk(code, chunk) {
@@ -2172,6 +2196,18 @@ function collectAssetDepsInner(
   }
 }
 
+function collectBundledCssAssetFileNames(
+  bundle: Rollup.OutputBundle,
+): string[] {
+  return Object.values(bundle)
+    .filter(
+      (output): output is Rollup.OutputAsset =>
+        output.type === 'asset' &&
+        output.originalFileNames?.includes('style.css'),
+    )
+    .map((output) => output.fileName)
+}
+
 //
 // css support
 //