drop unused react-dom modules

.changeset/shy-news-wave.md

@@ -0,0 +1,7 @@
+---
+"@opennextjs/cloudflare": patch
+---
+
+drop unused react-dom modules
+
+This saves ~500kB on the output bundle

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

@@ -23,6 +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 { patchRouteModules } from "./patches/plugins/route-module.js";
+import { shimReact } from "./patches/plugins/shim-react.js";
 import { setWranglerExternal } from "./patches/plugins/wrangler-external.js";
 import { copyPackageCliFiles, needsExperimentalReact, normalizePath } from "./utils/index.js";
 
@@ -92,6 +93,7 @@ export async function bundleServer(buildOpts: BuildOptions, projectOpts: Project
 		conditions: getOpenNextConfig(buildOpts).cloudflare?.useWorkerdCondition === false ? [] : ["workerd"],
 		plugins: [
 			shimRequireHook(buildOpts),
+			shimReact(buildOpts),
 			inlineDynamicRequires(updater, buildOpts),
 			setWranglerExternal(),
 			fixRequire(updater),

packages/cloudflare/src/cli/build/patches/plugins/require-hook.ts

@@ -7,9 +7,9 @@ import type { Plugin } from "esbuild";
 export function shimRequireHook(options: BuildOptions): Plugin {
 	const emptyShimPath = join(options.outputDir, "cloudflare-templates/shims/empty.js");
 	return {
-		name: "replaceRelative",
+		name: "require-hook-shim",
 		setup(build) {
-			// Note: we (empty) shim require-hook modules as they generate problematic code that uses requires
+			// We (empty) shim require-hook modules as they generate problematic code that uses requires
 			build.onResolve(
 				{ filter: getCrossPlatformPathRegex(String.raw`^\./require-hook$`, { escape: false }) },
 				() => ({

packages/cloudflare/src/cli/build/patches/plugins/shim-react.ts

@@ -0,0 +1,37 @@
+import { join } from "node:path";
+
+import type { BuildOptions } from "@opennextjs/aws/build/helper.js";
+import { getCrossPlatformPathRegex } from "@opennextjs/aws/utils/regex.js";
+import type { Plugin } from "esbuild";
+
+/**
+ * `react-dom/server.edge` requires:
+ * - `react-dom-server.edge.production.js`
+ * - `react-dom-server.browser.production.js`
+ * - `react-dom-server-legacy.browser.production.js`
+ *
+ * However only the first one is needed in the Cloudflare Workers environment.
+ * The other two can be shimmed to an empty module to reduce the bundle size.
+ *
+ * @param options Build options
+ * @returns An ESBuild plugin that shims unnecessary React modules
+ */
+export function shimReact(options: BuildOptions): Plugin {
+	const emptyShimPath = join(options.outputDir, "cloudflare-templates/shims/empty.js");
+	return {
+		name: "react-shim",
+		setup(build) {
+			build.onResolve(
+				{
+					filter: getCrossPlatformPathRegex(
+						String.raw`(react-dom-server\.browser\.production\.js|react-dom-server-legacy\.browser\.production\.js)$`,
+						{ escape: false }
+					),
+				},
+				() => ({
+					path: emptyShimPath,
+				})
+			);
+		},
+	};
+}