fix(build): eliminate Vite 8 treeshake.preset warning

examples/app-router-playground/vite.config.ts

@@ -83,29 +83,6 @@ export default defineConfig({
         childEnvironments: ["ssr"],
       },
     }),
-
-    // Vite 8 (rolldown) warns on rollup-only keys injected by vinext.
-    // Strip those keys from the resolved client build config.
-    {
-      name: "strip-rolldown-incompatible-rollup-options",
-      configResolved(config) {
-        const clientRollupOptions = (config as any).environments?.client?.build?.rollupOptions;
-        if (!clientRollupOptions) return;
-
-        if (
-          clientRollupOptions.treeshake &&
-          typeof clientRollupOptions.treeshake === "object" &&
-          !Array.isArray(clientRollupOptions.treeshake)
-        ) {
-          delete clientRollupOptions.treeshake.preset;
-        }
-
-        const output = clientRollupOptions.output;
-        if (output && typeof output === "object" && !Array.isArray(output)) {
-          delete output.experimentalMinChunkSize;
-        }
-      },
-    },
   ],
 
   resolve: {

packages/vinext/src/index.ts

@@ -598,6 +598,9 @@ const clientCodeSplittingConfig = {
  *   tryCatchDeoptimization: false, which can break specific libraries
  *   that rely on property access side effects or try/catch for feature detection
  * - 'recommended' + 'no-external' gives most of the benefit with less risk
+ *
+ * @deprecated Use getClientTreeshakeConfigForVite(viteMajorVersion) instead
+ * for Vite version compatibility. Kept for backward compatibility.
  */
 const clientTreeshakeConfig = {
   preset: "recommended" as const,
@@ -634,6 +637,42 @@ function getClientOutputConfigForVite(viteMajorVersion: number) {
     : clientOutputConfig;
 }
 
+/**
+ * Returns treeshake configuration appropriate for the Vite version.
+ *
+ * Rollup (Vite 7) supports presets like "recommended" which set multiple
+ * treeshake options at once. Rolldown (Vite 8+) doesn't support presets,
+ * so we only return moduleSideEffects for Vite 8+.
+ *
+ * The Rollup "recommended" preset sets:
+ * - annotations: true (Rolldown default is also true)
+ * - manualPureFunctions: [] (Rolldown default is also [])
+ * - propertyReadSideEffects: true (Rolldown equivalent is 'always', the default)
+ * - unknownGlobalSideEffects: false (Rolldown default is true — this is a known acceptable
+ *   divergence. Slightly less aggressive DCE on unknown globals, acceptable for client bundles)
+ * - correctVarValueBeforeDeclaration and tryCatchDeoptimization (Rolldown handles these differently)
+ *
+ * The key optimization is moduleSideEffects: "no-external", which is supported
+ * by both bundlers and provides the DCE benefits for barrel-exporting libraries.
+ * It treats node_modules as side-effect-free (enabling aggressive DCE) while
+ * preserving side effects in local code.
+ */
+function getClientTreeshakeConfigForVite(viteMajorVersion: number) {
+  if (viteMajorVersion >= 8) {
+    // Rolldown (Vite 8+) - no preset support, only specific options.
+    // Rolldown's built-in defaults already cover what Rollup's 'recommended'
+    // preset provides (annotations, correctContext, tryCatchDeoptimization).
+    return {
+      moduleSideEffects: "no-external" as const,
+    };
+  }
+  // Rollup (Vite 7) - supports presets for convenient option grouping
+  return {
+    preset: "recommended" as const,
+    moduleSideEffects: "no-external" as const,
+  };
+}
+
 type BundleBackfillChunk = {
   type: "chunk";
   fileName: string;
@@ -1441,14 +1480,16 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
                 };
               })(),
               // Enable aggressive tree-shaking for client builds.
-              // See clientTreeshakeConfig for rationale.
+              // See getClientTreeshakeConfigForVite JSDoc for rationale.
               // Only apply globally for standalone client builds (Pages Router
               // CLI). For multi-environment builds (App Router, Cloudflare),
               // treeshake is set per-environment on the client env below to
               // avoid leaking into RSC/SSR environments where
               // moduleSideEffects: 'no-external' could drop server packages
               // that rely on module-level side effects.
-              ...(!isSSR && !isMultiEnv ? { treeshake: clientTreeshakeConfig } : {}),
+              ...(!isSSR && !isMultiEnv
+                ? { treeshake: getClientTreeshakeConfigForVite(viteMajorVersion) }
+                : {}),
               // Code-split client bundles: separate framework (React/ReactDOM),
               // vinext runtime (shims), and vendor packages into their own
               // chunks so pages only load the JS they need.
@@ -1696,7 +1737,7 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
                 ...withBuildBundlerOptions(viteMajorVersion, {
                   input: { index: VIRTUAL_APP_BROWSER_ENTRY },
                   output: getClientOutputConfigForVite(viteMajorVersion),
-                  treeshake: clientTreeshakeConfig,
+                  treeshake: getClientTreeshakeConfigForVite(viteMajorVersion),
                 }),
               },
             },
@@ -1717,7 +1758,7 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
                 ...withBuildBundlerOptions(viteMajorVersion, {
                   input: { index: VIRTUAL_CLIENT_ENTRY },
                   output: getClientOutputConfigForVite(viteMajorVersion),
-                  treeshake: clientTreeshakeConfig,
+                  treeshake: getClientTreeshakeConfigForVite(viteMajorVersion),
                 }),
               },
             },
@@ -1743,7 +1784,7 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
                 ...withBuildBundlerOptions(viteMajorVersion, {
                   input: { index: VIRTUAL_CLIENT_ENTRY },
                   output: getClientOutputConfigForVite(viteMajorVersion),
-                  treeshake: clientTreeshakeConfig,
+                  treeshake: getClientTreeshakeConfigForVite(viteMajorVersion),
                 }),
               },
             },
@@ -4084,6 +4125,7 @@ export {
   clientTreeshakeConfig,
   computeLazyChunks,
   getClientOutputConfigForVite,
+  getClientTreeshakeConfigForVite,
 };
 export { augmentSsrManifestFromBundle as _augmentSsrManifestFromBundle };
 export { resolvePostcssStringPlugins as _resolvePostcssStringPlugins };

tests/build-optimization.test.ts

@@ -12,6 +12,7 @@ import { describe, it, expect, beforeEach, afterEach } from "vite-plus/test";
 import {
   clientManualChunks,
   clientTreeshakeConfig,
+  getClientTreeshakeConfigForVite,
   computeLazyChunks,
   _augmentSsrManifestFromBundle,
   _stripServerExports,
@@ -387,7 +388,6 @@ describe("treeshake config integration", () => {
 
       // treeshake should be set on bundler options for non-SSR builds
       expect(getBuildBundlerOptions(result).treeshake).toEqual({
-        preset: "recommended",
         moduleSideEffects: "no-external",
       });
     } finally {
@@ -479,7 +479,6 @@ describe("treeshake config integration", () => {
 
       // Client environment should have treeshake
       expect(getEnvBuildBundlerOptions(result.environments.client).treeshake).toEqual({
-        preset: "recommended",
         moduleSideEffects: "no-external",
       });
 
@@ -1632,3 +1631,34 @@ export const getStaticPaths = () => [
     expect(result).not.toContain("a;b");
   });
 });
+
+// ─── getClientTreeshakeConfigForVite ──────────────────────────────────────────
+
+describe("getClientTreeshakeConfigForVite", () => {
+  it("returns preset for Vite 7 (Rollup compatibility)", () => {
+    const config = getClientTreeshakeConfigForVite(7);
+    expect(config).toEqual({
+      preset: "recommended",
+      moduleSideEffects: "no-external",
+    });
+  });
+
+  it("returns config without preset for Vite 8 (Rolldown compatibility)", () => {
+    const config = getClientTreeshakeConfigForVite(8);
+    expect(config).toEqual({
+      moduleSideEffects: "no-external",
+    });
+  });
+
+  it("returns config without preset for Vite 9+", () => {
+    const config9 = getClientTreeshakeConfigForVite(9);
+    expect(config9).toEqual({
+      moduleSideEffects: "no-external",
+    });
+
+    const config10 = getClientTreeshakeConfigForVite(10);
+    expect(config10).toEqual({
+      moduleSideEffects: "no-external",
+    });
+  });
+});