fix(rollup): over-prefetching

Author: maiieul

.changeset/maiieul-manual-changeset-2.md

@@ -0,0 +1,5 @@
+---
+'@builder.io/qwik': patch
+---
+
+🐞 fix(rollup): improve manualChunks logic to minimize over-prefetching

packages/qwik/src/optimizer/src/plugins/plugin.ts

@@ -875,8 +875,47 @@ export const manifest = ${JSON.stringify(manifest)};\n`;
   // order by discovery time, so that related segments are more likely to group together
   function manualChunks(id: string, { getModuleInfo }: Rollup.ManualChunkMeta) {
     const module = getModuleInfo(id)!;
-    const segment = module.meta.segment as SegmentAnalysis | undefined;
-    return segment?.entry;
+    const segment = module.meta.segment;
+
+    if (segment) {
+      // We need to specifically return segment.entry for qwik-insights
+      return segment.entry;
+    }
+
+    // To prevent over-prefetching, we need to clearly seperate those chunks,
+    // otherwise rollup can bundle them together with the first component chunk it finds.
+    // For example, the core code could go into an Accordion.tsx chunk, which would make the whole app import accordion related chunks everywhere.
+    if (/\/(qwik|core)\/dist\/core.*js$/.test(id) || id.includes('@builder.io/qwik/build')) {
+      return 'core';
+    }
+    if (/\/(qwik-city|router)\/lib\/index.qwik.*js$/.test(id)) {
+      return 'qwik-city';
+    }
+    if (id.endsWith('vite/preload-helper.js')) {
+      return 'preload-helper';
+    }
+
+    // We can't return a chunk for each module as that creates too many small chunks that slow down the prefetching as well,
+    // nor can we bundle related node_modules together (e.g. all shiki modules together), as that can create very big 10MB chunks.
+    // So here we let rollup do its job.
+    if (id.includes('node_modules')) {
+      return null;
+    }
+
+    // Also to prevent over-prefetching, we must clearly separate those chunks so that rollup doesn't add additional imports into entry files.
+    // We do this after the node_modules check, because some node_modules can end with .js, .ts, etc.
+    if (/\.(qwik\.mjs|qwik\.cjs|tsx|jsx|mdx|ts|js)$/.test(id)) {
+      const optimizer = getOptimizer();
+      const path = optimizer.sys.path;
+      const relativePath = path.relative(optimizer.sys.cwd(), id);
+      const sanitizedPath = relativePath
+        .replace(/^(\.\.\/)+/, '')
+        .replace(/^\/+/, '')
+        .replace(/\//g, '-');
+      return sanitizedPath; // We return sanitizedPath for qwikVite plugin with debug:true
+    }
+
+    return null;
   }
 
   return {