fix: detect shared chunks via moduleIds and imported css instead of isDynamicEntry

.changeset/deep-sails-peel.md

@@ -0,0 +1,5 @@
+---
+"@solidjs/start": patch
+---
+
+Fixed shared chunk css not being server rendered in production (Vite 8 regression).

apps/fixtures/css/vite.config.ts

@@ -13,13 +13,14 @@ export default defineConfig({
          * 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";
+        codeSplitting: {
+          groups: [
+            {
+              name: "shared-css",
+              test: "src/components/sharedChunk",
+            },
+          ],
         },
       },
     },

packages/start/src/config/lazy.ts

@@ -73,12 +73,16 @@ const lazy = (): PluginOption => {
       if (this.environment.name !== VITE_ENVIRONMENTS.client) return;
 
       for (const chunk of Object.values(bundle)) {
-        if (chunk.type !== "chunk" || !chunk.isDynamicEntry || chunk.facadeModuleId) continue;
+        if (chunk.type !== "chunk" || chunk.facadeModuleId) continue;
+        if (!chunk.viteMetadata?.importedCss.size) continue;
+
+        const moduleIds = chunk.moduleIds.filter(id => !id.endsWith("css"));
+        if (moduleIds.length <= 1) 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) {
+        for (const id of moduleIds) {
           sharedChunkNames[id] = chunkName;
         }
       }