fix: collect css with shared chunk name

.changeset/eight-months-camp.md

@@ -0,0 +1,5 @@
+---
+"@solidjs/start": patch
+---
+
+Fixed CSS from shared chunks not being collected via the chunk name.

apps/fixtures/css/src/components/sharedChunk/lazy1.tsx

@@ -0,0 +1,5 @@
+import "../../styles/sharedChunk.css";
+
+export default () => {
+  return <></>;
+};

apps/fixtures/css/src/components/sharedChunk/lazy2.tsx

@@ -0,0 +1,3 @@
+export default () => {
+  return <></>;
+};

apps/fixtures/css/src/components/test.tsx

@@ -101,6 +101,19 @@ export const CommonTests = (props: { routeModuleClass?: string }) => (
         </>
       }
     />
+    <Test
+      component="SharedChunk"
+      file="sharedChunk.css"
+      class="sharedChunk"
+      integration="import"
+      lazy
+      comment={
+        <>
+          Tests if CSS from shared chunks is server rendered properly. Rollup occasionally combines
+          modules into such shared chunks.
+        </>
+      }
+    />
   </>
 );
 

apps/fixtures/css/src/routes/index.tsx

@@ -14,6 +14,11 @@ const LazyLinkTmp = lazy(() => import("../components/lazyLinkTmp"));
 const entries = import.meta.glob("../components/lazyG*.tsx");
 const LazyGlob = lazy(Object.values(entries)[0] as any);
 
+const SharedChunk = lazy(() => import("../components/sharedChunk/lazy1"));
+// Do not remove this.
+// Rollup only creates a shared chunk if there are atleast two modules.
+lazy(() => import("../components/sharedChunk/lazy2"));
+
 const getData = query(async () => {
   "use server";
   await new Promise(res => setTimeout(res, 1000));
@@ -35,6 +40,7 @@ export default function Home() {
       <Show when={!data()}>
         <LazyLinkTmp />
       </Show>
+      <SharedChunk />
 
       <Layout title="CSS Tests">
         <CommonTests routeModuleClass={classes["route"]} />

apps/fixtures/css/src/styles/sharedChunk.css

@@ -0,0 +1,3 @@
+.sharedChunk {
+  background-color: var(--color-success);
+}

apps/fixtures/css/vite.config.ts

@@ -5,4 +5,22 @@ import { solidStart } from "../../../packages/start/src/config";
 
 export default defineConfig({
   plugins: [solidStart(), nitroV2Plugin(), tailwindcss()],
+  build: {
+    rollupOptions: {
+      output: {
+        /**
+         * Creates a shared chunk with two components. Needed for the "SharedChunk" test!
+         * The vite manifest behaves differently for such shared chunks.
+         * More info: packages/start/src/config/lazy.ts
+         *
+         * TODO: When switching to Rolldown, migrate this to advancedChunks
+         * https://vite.dev/guide/rolldown.html#manualchunks-to-advancedchunks
+         */
+        manualChunks(id) {
+          if (!id.includes("src/components/sharedChunk")) return;
+          return "shared";
+        },
+      },
+    },
+  },
 });

packages/start/src/config/lazy.ts

@@ -48,13 +48,43 @@ const fileEndingRegex = /(ts|js)x(\?.*)?$/;
 
 const lazy = (): PluginOption => {
   const cwd = process.cwd().replaceAll(osSep, sep);
+
+  /**
+   * Maps module ids to their client-specific shared chunk names.
+   * Modules in shared chunks need to find their assets via the chunk name, instead of their module id.
+   *
+   * Vite includes assets of such modules in the manifest via the chunk name:
+   * https://github.com/vitejs/vite/blob/4be37a8389c67873880f826b01fe40137e1c29a7/packages/vite/src/node/plugins/manifest.ts#L179
+   * https://github.com/vitejs/vite/blob/4be37a8389c67873880f826b01fe40137e1c29a7/packages/vite/src/node/plugins/manifest.ts#L319
+   *
+   * Rollup occassionally creates shared chunks automatically,
+   * but they can also be manually created by the user via:
+   * https://rollupjs.org/configuration-options/#output-manualchunks
+   *
+   * More infos on Rollup's logic:
+   * https://github.com/rollup/rollup/issues/3772#issuecomment-689955168
+   */
+  const sharedChunkNames: Record<string, string> = {};
+
   return {
     name: "solid-lazy-css",
     enforce: "pre",
-    applyToEnvironment(env) {
-      return env.name === VITE_ENVIRONMENTS.server;
+    generateBundle(_, bundle) {
+      if (this.environment.name !== VITE_ENVIRONMENTS.client) return;
+
+      for (const chunk of Object.values(bundle)) {
+        if (chunk.type !== "chunk" || !chunk.isDynamicEntry || chunk.facadeModuleId) continue;
+
+        // Has to follow Vites implementation:
+        // https://github.com/vitejs/vite/blob/4be37a8389c67873880f826b01fe40137e1c29a7/packages/vite/src/node/plugins/manifest.ts#L179
+        const chunkName = `_${basename(chunk.fileName)}`;
+        for (const id of chunk.moduleIds) {
+          sharedChunkNames[id] = chunkName;
+        }
+      }
     },
     async transform(src, id) {
+      if (this.environment.name !== VITE_ENVIRONMENTS.server) return;
       if (!id.match(fileEndingRegex)) return;
 
       // The transformed files either import "lazy" or css files
@@ -66,7 +96,8 @@ const lazy = (): PluginOption => {
       const hasDefaultExport = src.indexOf("export default") !== -1;
       if (hasDefaultExport) {
         const localId = relative(cwd, id);
-        plugins.push(idTransform(localId));
+        const chunkName = sharedChunkNames[id];
+        plugins.push(idTransform(chunkName ?? localId));
       }
 
       const hasLazy = src.indexOf("lazy(") !== -1;