fix: silent IMPORT_IS_UNDEFINED for proxy.ts

packages/vinext/src/index.ts

@@ -1472,6 +1472,23 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
                   ) {
                     return;
                   }
+                  // proxy.ts / middleware.ts may export either a named handler
+                  // or default export. The generated virtual entries probe both
+                  // forms and validate at runtime, which can trigger noisy
+                  // IMPORT_IS_UNDEFINED warnings when only one form exists.
+                  // Match any file extension because findMiddlewareFile() scans
+                  // all configured pageExtensions, not just .ts/.js.
+                  if (
+                    warning.code === "IMPORT_IS_UNDEFINED" &&
+                    /Import `(?:default|proxy|middleware)` will always be undefined/.test(
+                      warning.message ?? "",
+                    ) &&
+                    /\b(?:proxy|middleware)\.\w+\b/.test(warning.message ?? "") &&
+                    (warning.message?.includes("virtual:vinext-rsc-entry") ||
+                      warning.message?.includes("virtual:vinext-server-entry"))
+                  ) {
+                    return;
+                  }
                   if (userOnwarn) {
                     userOnwarn(warning, defaultHandler);
                   } else {

tests/pages-router.test.ts

@@ -1444,6 +1444,81 @@ describe("Plugin config", () => {
     expect(defaultHandler).toHaveBeenCalledWith(otherWarning);
   });
 
+  it("suppresses IMPORT_IS_UNDEFINED noise for generated proxy/middleware fallback probes", async () => {
+    const plugins = vinext() as any[];
+    const configPlugin = plugins.find((p) => p.name === "vinext:config");
+    expect(configPlugin).toBeDefined();
+
+    const result = await configPlugin.config({ root: FIXTURE_DIR, plugins: [] });
+
+    expect(result.build).toBeDefined();
+    const bundlerOptions = getBuildBundlerOptions(result);
+    expect(bundlerOptions).toBeDefined();
+    expect(bundlerOptions.onwarn).toBeDefined();
+
+    const defaultHandler = vi.fn();
+
+    bundlerOptions.onwarn(
+      {
+        code: "IMPORT_IS_UNDEFINED",
+        message:
+          "[IMPORT_IS_UNDEFINED] Warning: Import `default` will always be undefined because there is no matching export in 'proxy.ts'\\n      ╭─[ \\0virtual:vinext-rsc-entry:2632:34 ]",
+      },
+      defaultHandler,
+    );
+    expect(defaultHandler).not.toHaveBeenCalled();
+
+    bundlerOptions.onwarn(
+      {
+        code: "IMPORT_IS_UNDEFINED",
+        message:
+          "[IMPORT_IS_UNDEFINED] Warning: Import `default` will always be undefined because there is no matching export in 'middleware.ts'\\n      ╭─[ \\0virtual:vinext-server-entry:168:34 ]",
+      },
+      defaultHandler,
+    );
+    expect(defaultHandler).not.toHaveBeenCalled();
+
+    bundlerOptions.onwarn(
+      {
+        code: "IMPORT_IS_UNDEFINED",
+        message:
+          "[IMPORT_IS_UNDEFINED] Warning: Import `proxy` will always be undefined because there is no matching export in 'proxy.tsx'\\n      ╭─[ \\0virtual:vinext-rsc-entry:2632:34 ]",
+      },
+      defaultHandler,
+    );
+    expect(defaultHandler).not.toHaveBeenCalled();
+
+    bundlerOptions.onwarn(
+      {
+        code: "IMPORT_IS_UNDEFINED",
+        message:
+          "[IMPORT_IS_UNDEFINED] Warning: Import `middleware` will always be undefined because there is no matching export in 'middleware.jsx'\\n      ╭─[ \\0virtual:vinext-server-entry:168:34 ]",
+      },
+      defaultHandler,
+    );
+    expect(defaultHandler).not.toHaveBeenCalled();
+
+    bundlerOptions.onwarn(
+      {
+        code: "IMPORT_IS_UNDEFINED",
+        message:
+          "[IMPORT_IS_UNDEFINED] Warning: Import `default` will always be undefined because there is no matching export in 'some-user-file.ts'",
+      },
+      defaultHandler,
+    );
+    expect(defaultHandler).toHaveBeenCalledTimes(1);
+
+    bundlerOptions.onwarn(
+      {
+        code: "IMPORT_IS_UNDEFINED",
+        message:
+          "[IMPORT_IS_UNDEFINED] Warning: Import `proxy` will always be undefined because there is no matching export in 'some-user-file.ts'",
+      },
+      defaultHandler,
+    );
+    expect(defaultHandler).toHaveBeenCalledTimes(2);
+  });
+
   it("preserves user-supplied build.rollupOptions.onwarn", async () => {
     const plugins = vinext() as any[];
     const configPlugin = plugins.find((p) => p.name === "vinext:config");