fix(build)!: remove custom moduleSideEffects config (#4164)

pi0 · web-flow · commit 55f30f487293 · 2026-03-30T00:30:34.000+02:00
diff --git a/docs/3.config/0.index.md b/docs/3.config/0.index.md
@@ -976,18 +976,6 @@ export default defineNitroConfig({
 });
 ```
 
-### `moduleSideEffects`
-
-Default: `['unenv/polyfill/']`
-
-Specifies module imports that have side-effects.
-
-```ts
-export default defineNitroConfig({
-  moduleSideEffects: ["unenv/polyfill/", "reflect-metadata"],
-});
-```
-
 ### `replace`
 
 Build-time string replacements.
diff --git a/docs/4.examples/vite-ssr-vue-router.md b/docs/4.examples/vite-ssr-vue-router.md
@@ -48,6 +48,7 @@ export default defineConfig((_env) => ({
   environments: {
     client: { build: { rollupOptions: { input: "./app/entry-client.ts" } } },
     ssr: { build: { rollupOptions: { input: "./app/entry-server.ts" } } },
+    nitro: { build: { rollupOptions: { treeshake: { moduleSideEffects: () => false } } } },
   },
 }));
 
diff --git a/examples/vite-ssr-vue-router/vite.config.mjs b/examples/vite-ssr-vue-router/vite.config.mjs
@@ -8,6 +8,7 @@ export default defineConfig((_env) => ({
   environments: {
     client: { build: { rollupOptions: { input: "./app/entry-client.ts" } } },
     ssr: { build: { rollupOptions: { input: "./app/entry-server.ts" } } },
+    nitro: { build: { rollupOptions: { treeshake: { moduleSideEffects: () => false } } } },
   },
 }));
 
diff --git a/src/build/rolldown/config.ts b/src/build/rolldown/config.ts
@@ -38,11 +38,6 @@ export const getRolldownConfig = async (nitro: Nitro): Promise<RolldownOptions>
         warn(warning);
       }
     },
-    treeshake: {
-      moduleSideEffects(id) {
-        return nitro.options.moduleSideEffects.some((p) => id.startsWith(p));
-      },
-    },
     optimization: {
       inlineConst: true,
     },
diff --git a/src/build/rollup/config.ts b/src/build/rollup/config.ts
@@ -56,11 +56,6 @@ export const getRollupConfig = async (nitro: Nitro): Promise<RollupConfig> => {
         rollupWarn(warning);
       }
     },
-    treeshake: {
-      moduleSideEffects(id) {
-        return nitro.options.moduleSideEffects.some((p) => id.startsWith(p));
-      },
-    },
     output: {
       format: "esm",
       entryFileNames: "index.mjs",
diff --git a/src/build/vite/bundler.ts b/src/build/vite/bundler.ts
@@ -21,11 +21,6 @@ export const getBundlerConfig = async (
     input: nitro.options.entry,
     external: [...base.env.external],
     plugins: [...(await baseBuildPlugins(nitro, base))].filter(Boolean) as RollupPlugin[],
-    treeshake: {
-      moduleSideEffects(id) {
-        return nitro.options.moduleSideEffects.some((p) => id.startsWith(p));
-      },
-    },
     onwarn(warning, warn) {
       if (!base.ignoreWarningCodes.has(warning.code || "")) {
         warn(warning);
diff --git a/src/config/defaults.ts b/src/config/defaults.ts
@@ -69,7 +69,6 @@ export const NitroDefaults: NitroConfig = {
 
   // Builder
   builder: undefined,
-  moduleSideEffects: ["unenv/polyfill/"],
   replace: {},
   node: true,
   sourcemap: false,
diff --git a/src/presets/cloudflare/preset.ts b/src/presets/cloudflare/preset.ts
@@ -37,6 +37,25 @@ function guardCreateRequire(): Plugin {
   };
 }
 
+// When code-splitting is enabled, bundlers hoist externalized `node:*` built-in
+// imports as bare side-effect imports (`import "node:buffer"`) into entry and
+// chunk files. These are no-ops (Node.js built-ins have no meaningful
+// module-level side effects) but they can cause issues on worker runtimes where
+// `node:*` modules may not be available or trigger unnecessary warnings.
+const BARE_NODE_IMPORT_RE = /^import\s*['"]node:[^'"]+['"];?\s*$/gm;
+function stripBareNodeImports(): Plugin {
+  return {
+    name: "nitro:cloudflare-strip-bare-node-imports",
+    generateBundle(_options, bundle) {
+      for (const chunk of Object.values(bundle)) {
+        if (chunk.type === "chunk" && chunk.code.includes("node:")) {
+          chunk.code = chunk.code.replace(BARE_NODE_IMPORT_RE, "");
+        }
+      }
+    },
+  };
+}
+
 export type { CloudflareOptions as PresetOptions } from "./types.ts";
 
 const cloudflarePages = defineNitroPreset(
@@ -69,7 +88,7 @@ const cloudflarePages = defineNitroPreset(
         format: "esm",
         inlineDynamicImports: false,
       },
-      plugins: [guardCreateRequire()],
+      plugins: [guardCreateRequire(), stripBareNodeImports()],
     },
     hooks: {
       "build:before": async (nitro) => {
@@ -149,7 +168,7 @@ const cloudflareModule = defineNitroPreset(
         exports: "named",
         inlineDynamicImports: false,
       },
-      plugins: [guardCreateRequire()],
+      plugins: [guardCreateRequire(), stripBareNodeImports()],
     },
     wasm: {
       lazy: false,
diff --git a/src/types/config.ts b/src/types/config.ts
@@ -223,7 +223,6 @@ export interface NitroOptions extends PresetOptions {
   inlineDynamicImports: boolean;
   sourcemap: boolean;
   node: boolean;
-  moduleSideEffects: string[];
   oxc?: OXCOptions;
   replace: Record<string, string | ((id: string) => string)>;
   commonJS?: RollupCommonJSOptions;
diff --git a/test/examples.test.ts b/test/examples.test.ts
@@ -53,6 +53,10 @@ function setupTest(name: string) {
       test(`${name} (${mode})`, async () => {
         const res = await ctx.fetch("/");
         const expectedStatus = name === "custom-error-handler" ? 500 : 200;
+        if (res.status !== expectedStatus) {
+          const text = await res.text();
+          console.error(`Unexpected response ${res.status} ${res.statusText}\n${text}`);
+        }
         expect(res.status, res.statusText).toBe(expectedStatus);
       });
     }
diff --git a/test/minimal/minimal.test.ts b/test/minimal/minimal.test.ts
@@ -11,8 +11,8 @@ const tmpDir = fileURLToPath(new URL(".tmp", import.meta.url));
 // Rounded up
 const bundleSizes: Record<string, [kb: number, minKB: number]> = {
   rollup: [16, 8],
-  rolldown: [16, 8],
-  vite: [16, 8],
+  rolldown: [19, 10],
+  vite: [19, 10],
   vite7: [16, 8],
 };
 
diff --git a/test/vite/side-effects-fixture/nitro.config.ts b/test/vite/side-effects-fixture/nitro.config.ts
@@ -0,0 +1,5 @@
+import { defineConfig } from "nitro";
+
+export default defineConfig({
+  preset: "standard",
+});
diff --git a/test/vite/side-effects-fixture/server.ts b/test/vite/side-effects-fixture/server.ts
@@ -0,0 +1,8 @@
+import "./server/utils/register-items.ts";
+import { getItems } from "./server/utils/registry.ts";
+
+export default {
+  fetch(_req: Request) {
+    return Response.json({ items: getItems() });
+  },
+};
diff --git a/test/vite/side-effects-fixture/server/utils/register-items.ts b/test/vite/side-effects-fixture/server/utils/register-items.ts
@@ -0,0 +1,4 @@
+import { registerItem } from "./registry.ts";
+
+registerItem("a");
+registerItem("b");
diff --git a/test/vite/side-effects-fixture/server/utils/registry.ts b/test/vite/side-effects-fixture/server/utils/registry.ts
@@ -0,0 +1,9 @@
+const items: string[] = [];
+
+export function registerItem(item: string) {
+  items.push(item);
+}
+
+export function getItems() {
+  return items;
+}
diff --git a/test/vite/side-effects-fixture/vite.config.ts b/test/vite/side-effects-fixture/vite.config.ts
@@ -0,0 +1,6 @@
+import { defineConfig } from "vite";
+import { nitro } from "nitro/vite";
+
+export default defineConfig({
+  plugins: [nitro()],
+});
diff --git a/test/vite/side-effects.test.ts b/test/vite/side-effects.test.ts
@@ -0,0 +1,40 @@
+import { fileURLToPath } from "node:url";
+import { join } from "node:path";
+import { rm, mkdir } from "node:fs/promises";
+import { describe, expect, it } from "vitest";
+import { createNitro, build, prepare } from "nitro/builder";
+
+const fixtureDir = fileURLToPath(new URL("./side-effects-fixture", import.meta.url));
+const tmpDir = fileURLToPath(new URL("./side-effects-fixture/.tmp", import.meta.url));
+
+describe("side-effects", () => {
+  for (const builder of ["rolldown", "rollup", "vite"] as const) {
+    describe(builder, () => {
+      let outDir: string;
+
+      it("build", async () => {
+        outDir = join(tmpDir, builder);
+        await rm(outDir, { recursive: true, force: true });
+        await mkdir(outDir, { recursive: true });
+        const nitro = await createNitro({
+          rootDir: fixtureDir,
+          output: { dir: outDir },
+          // @ts-expect-error for testing
+          __vitePkg__: builder,
+          builder: builder === "vite" ? "vite" : builder,
+        });
+        await prepare(nitro);
+        await build(nitro);
+      });
+
+      it("preserves side-effect imports", async () => {
+        const entry = join(outDir, "server/index.mjs");
+        const { fetch } = await import(entry).then((m) => m.default);
+        const res = await fetch(new Request("http://localhost/"));
+        expect(res.status).toBe(200);
+        const data = await res.json();
+        expect(data).toMatchObject({ items: ["a", "b"] });
+      });
+    });
+  }
+});
