define __NEXT_EXPERIMENTAL_REACT to reduce bundle size

Author: conico974

packages/cloudflare/src/cli/build/bundle-server.ts

@@ -23,7 +23,7 @@ import { patchDepdDeprecations } from "./patches/plugins/patch-depd-deprecations
 import { fixRequire } from "./patches/plugins/require.js";
 import { shimRequireHook } from "./patches/plugins/require-hook.js";
 import { setWranglerExternal } from "./patches/plugins/wrangler-external.js";
-import { normalizePath, patchCodeWithValidations } from "./utils/index.js";
+import { needsExperimentalReact, normalizePath, patchCodeWithValidations } from "./utils/index.js";
 
 /** The dist directory of the Cloudflare adapter package */
 const packageDistDir = path.join(path.dirname(fileURLToPath(import.meta.url)), "../..");
@@ -139,7 +139,8 @@ export async function bundleServer(buildOpts: BuildOptions): Promise<void> {
       "process.env.NEXT_RUNTIME": '"nodejs"',
       "process.env.NODE_ENV": '"production"',
       "process.env.TURBOPACK": "false",
-      // Ideally here we should define the `process.env.__NEXT_EXPERIMENTAL_REACT`, but this would require that function splitting is enabled for the case where both versions are needed (i.e. page and app router routes)
+      // This define should be safe to use for Next 14.2+
+      "process.env.__NEXT_EXPERIMENTAL_REACT": `${needsExperimentalReact(nextConfig)}`,
     },
     platform: "node",
     banner: {

packages/cloudflare/src/cli/build/utils/index.ts

@@ -2,4 +2,5 @@ export * from "./apply-patches.js";
 export * from "./create-config-files.js";
 export * from "./ensure-cf-config.js";
 export * from "./extract-project-env-vars.js";
+export * from "./needs-experimental-react.js";
 export * from "./normalize-path.js";

packages/cloudflare/src/cli/build/utils/needs-experimental-react.ts

@@ -0,0 +1,19 @@
+import type { NextConfig } from "@opennextjs/aws/types/next-types";
+
+// Not sure if this should be upstreamed to aws
+// Adding more stuff there make typing incorrect actually, these properties are never undefined as long as it is the right version of next
+// Ideally we'd have different `NextConfig` types for different versions of next
+interface ExtendedNextConfig extends NextConfig {
+  experimental: {
+    ppr?: boolean;
+    taint?: boolean;
+    viewTransition?: boolean;
+    serverActions?: boolean;
+  };
+}
+
+// Copied from https://github.com/vercel/next.js/blob/4518bc91641a0fd938664b781e12ae7c145f3396/packages/next/src/lib/needs-experimental-react.ts#L3-L6
+export function needsExperimentalReact(nextConfig: ExtendedNextConfig) {
+  const { ppr, taint, viewTransition } = nextConfig.experimental || {};
+  return Boolean(ppr || taint || viewTransition);
+}