fix: restore noDiscovery and convert CJS require() to imports for client

The dependency optimizer causes duplicate preact instances when remote
(JSR) islands resolve deps to /@fs/ paths while the optimizer bundles
to /.vite/deps/. Restore noDiscovery: true to prevent this.

For CJS packages used in client-side islands (like mime-db), convert
require() calls to ESM import statements via regex so browsers can
load them. The SSR shim continues to use Node.js createRequire.

All tests pass: 36/36 dev, 31/31 build, 15/15 patches.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: bartlomieju

packages/plugin-vite/src/mod.ts

@@ -150,23 +150,13 @@ export function fresh(config?: FreshViteConfig): Plugin[] {
           },
 
           optimizeDeps: {
-            // Exclude preact ecosystem from optimizer to prevent
-            // duplicate instances with remote (JSR) islands. JSR
-            // islands resolve deps to /@fs/ paths, so if the
-            // optimizer also bundles them to /.vite/deps/, two
-            // separate instances load. Other CJS packages (like
-            // mime-db) are optimized normally.
-            exclude: [
-              "preact",
-              "preact/hooks",
-              "preact/jsx-runtime",
-              "preact/jsx-dev-runtime",
-              "preact/debug",
-              "preact/compat",
-              "@preact/signals",
-              "@preact/signals-core",
-              "preact-render-to-string",
-            ],
+            // Disable dep optimizer because deno.ts handles all
+            // module resolution. The optimizer causes duplicate
+            // module instances when remote (JSR) islands resolve
+            // deps to /@fs/ paths while the optimizer bundles to
+            // /.vite/deps/. CJS packages in client-side islands
+            // are handled by deno.ts's load hook.
+            noDiscovery: true,
           },
 
           publicDir: pathWithRoot(fConfig.staticDir[0], config.root),

packages/plugin-vite/src/plugins/deno.ts

@@ -206,23 +206,50 @@ export function deno(): Plugin {
           ) {
             const isServer =
               this.environment.config.consumer === "server";
-            const preamble = isServer
-              ? `import { createRequire as __cjs_createRequire } from "node:module";
+
+            if (isServer) {
+              // SSR: use Node.js createRequire for full CJS compat
+              const wrapped = `
+import { createRequire as __cjs_createRequire } from "node:module";
 import { fileURLToPath as __cjs_fileURLToPath } from "node:url";
 import { dirname as __cjs_dirname } from "node:path";
 var __filename = __cjs_fileURLToPath(import.meta.url);
 var __dirname = __cjs_dirname(__filename);
-var require = __cjs_createRequire(import.meta.url);`
-              : `var __filename = "";
-var __dirname = "";
-var require = (id) => { throw new Error("require() not supported in browser: " + id); };`;
-
-            const wrapped = `${preamble}
+var require = __cjs_createRequire(import.meta.url);
 var module = { exports: {} };
 var exports = module.exports;
 
 ${code}
 
+export default module.exports;
+`;
+              return { code: wrapped };
+            }
+
+            // Client: convert require() calls to ESM imports so
+            // browsers can load them. Hoist static require() calls
+            // to import statements at the top.
+            const imports: string[] = [];
+            let idx = 0;
+            const transformed = code.replace(
+              /\brequire\(["']([^"']+)["']\)/g,
+              (_match: string, spec: string) => {
+                const varName = `__cjs_import_${idx++}`;
+                imports.push(
+                  `import ${varName} from ${JSON.stringify(spec)};`,
+                );
+                return `(${varName}.default ?? ${varName})`;
+              },
+            );
+
+            const wrapped = `${imports.join("\n")}
+var module = { exports: {} };
+var exports = module.exports;
+var __filename = "";
+var __dirname = "";
+
+${transformed}
+
 export default module.exports;
 `;
             return { code: wrapped };