From 88fcf1246a1bf93f6eaea2f3dd3d9f201c9ec49f Mon Sep 17 00:00:00 2001
From: yyh <yuanyouhuilyz@gmail.com>
Date: Sat, 11 Jul 2026 21:48:22 +0800
Subject: [PATCH 1/2] fix(config): keep page extensions out of module
 resolution

---
 packages/vinext/src/index.ts                  |  2 +-
 packages/vinext/src/routing/file-matcher.ts   | 36 ++------
 tests/app-router-route-file-collision.test.ts | 64 +++++++++++++
 .../app-route-file-collision/agents.md        |  1 +
 .../app/agents/page.tsx                       |  3 +
 .../app/custom-extension/page.mdx             |  1 +
 .../app-route-file-collision/app/layout.tsx   |  7 ++
 .../app-route-file-collision/next.config.mjs  |  3 +
 tests/page-extensions-resolve.test.ts         | 89 ++++---------------
 9 files changed, 107 insertions(+), 99 deletions(-)
 create mode 100644 tests/app-router-route-file-collision.test.ts
 create mode 100644 tests/fixtures/app-route-file-collision/agents.md
 create mode 100644 tests/fixtures/app-route-file-collision/app/agents/page.tsx
 create mode 100644 tests/fixtures/app-route-file-collision/app/custom-extension/page.mdx
 create mode 100644 tests/fixtures/app-route-file-collision/app/layout.tsx
 create mode 100644 tests/fixtures/app-route-file-collision/next.config.mjs

diff --git a/packages/vinext/src/index.ts b/packages/vinext/src/index.ts
index 026947e709..ab84094b90 100644
--- a/packages/vinext/src/index.ts
+++ b/packages/vinext/src/index.ts
@@ -3273,7 +3273,7 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
         // `.cjs`/`.cts` if they need extensionless imports of CJS config files.
         const extensions =
           configuredExtensions === null
-            ? buildViteResolveExtensions(nextConfig.pageExtensions, config.resolve?.extensions)
+            ? buildViteResolveExtensions(config.resolve?.extensions)
             : normalizeViteResolveExtensions(configuredExtensions);
         config.resolve ??= {};
         config.resolve.extensions = extensions;
diff --git a/packages/vinext/src/routing/file-matcher.ts b/packages/vinext/src/routing/file-matcher.ts
index 2aae70f324..81c5154356 100644
--- a/packages/vinext/src/routing/file-matcher.ts
+++ b/packages/vinext/src/routing/file-matcher.ts
@@ -110,40 +110,22 @@ export function findFileWithExts(
 }
 
 /**
- * Vite's default `resolve.extensions` covers `.tsx/.ts/.jsx/.js/.json` (and
- * `.mjs/.mts`). When the user configures `pageExtensions` with values Vite
- * does not know about — e.g. `["platform.tsx", "tsx", "mdx"]` from the
- * Next.js `resolve-extensions` fixture — extensionless imports of those
- * files fail to resolve, and the build crashes with "Custom deploy script
- * failed: undefined (1)".
+ * Add the config extensions produced by `vinext init` to Vite's resolver.
  *
- * Build the merged extension list that Vite should use:
+ * `pageExtensions` is intentionally not part of module resolution. Next.js
+ * uses it to discover route files; custom module extensions are configured
+ * separately through `turbopack.resolveExtensions` or webpack
+ * `resolve.extensions`.
  *
- *  1. User-configured pageExtensions go first (each prefixed with `.`) so
- *     the user's priority wins. e.g. `.platform.tsx` resolves before `.tsx`.
- *  2. Vite's defaults follow, with duplicates removed.
- *  3. `.cjs`/`.cts` go last (lowest priority). Neither Vite's defaults nor the
- *     user's pageExtensions include them, but `vinext init` renames CJS config
- *     files (e.g. `tailwind.config.js` → `tailwind.config.cjs`) when it adds
- *     `"type": "module"`, and app code imports those extensionlessly
- *     (`import cfg from "../tailwind.config"`). Without these, the bundle fails
- *     with "[UNRESOLVED_IMPORT] Could not resolve '../tailwind.config'".
- *
- * The user's pageExtensions retain their relative order, which is what
- * Next.js / Turbopack do via the `resolveExtensions` config option.
- *
- * See: cloudflare/vinext#1502 for page-extension ordering, and
- * cloudflare/vinext#2435 for extensionless `.cjs` config imports.
+ * `.cjs`/`.cts` go last because `vinext init` renames CJS config files when it
+ * adds `"type": "module"`, and app code may import those files extensionlessly.
  */
 export function buildViteResolveExtensions(
-  pageExtensions?: readonly string[] | null,
-  viteDefaults: readonly string[] = [".mjs", ".js", ".mts", ".ts", ".jsx", ".tsx", ".json"],
+  viteExtensions: readonly string[] = [".mjs", ".js", ".mts", ".ts", ".jsx", ".tsx", ".json"],
 ): string[] {
-  const normalized = normalizePageExtensions(pageExtensions);
-  const dotted = normalized.map((ext) => `.${ext}`);
   const seen = new Set<string>();
   const result: string[] = [];
-  for (const ext of [...dotted, ...viteDefaults, ".cjs", ".cts"]) {
+  for (const ext of [...viteExtensions, ".cjs", ".cts"]) {
     if (seen.has(ext)) continue;
     seen.add(ext);
     result.push(ext);
diff --git a/tests/app-router-route-file-collision.test.ts b/tests/app-router-route-file-collision.test.ts
new file mode 100644
index 0000000000..b63c9ebda2
--- /dev/null
+++ b/tests/app-router-route-file-collision.test.ts
@@ -0,0 +1,64 @@
+import fs from "node:fs/promises";
+import path from "node:path";
+import type { ViteDevServer } from "vite";
+import { afterAll, beforeAll, describe, expect, it } from "vite-plus/test";
+import {
+  createRscRequestHeaders,
+  createRscRequestUrl,
+} from "../packages/vinext/src/server/app-rsc-cache-busting.js";
+import { createIsolatedFixture, startFixtureServer } from "./helpers.js";
+
+const FIXTURE_DIR = path.resolve(import.meta.dirname, "./fixtures/app-route-file-collision");
+
+describe("App Router route and project file collisions", () => {
+  let server: ViteDevServer;
+  let baseUrl: string;
+  let fixtureDir: string;
+
+  beforeAll(async () => {
+    fixtureDir = await createIsolatedFixture(FIXTURE_DIR, "vinext-route-file-collision-");
+    ({ server, baseUrl } = await startFixtureServer(fixtureDir));
+  }, 30000);
+
+  afterAll(async () => {
+    await server?.close();
+    if (fixtureDir) await fs.rm(fixtureDir, { recursive: true, force: true });
+  });
+
+  it("does not let a custom page extension shadow an HTML route request", async () => {
+    const response = await fetch(`${baseUrl}/agents`);
+    const body = await response.text();
+
+    expect(response.status).toBe(200);
+    expect(response.headers.get("content-type")).toContain("text/html");
+    expect(body).toContain("Agents route response");
+    expect(body).not.toContain("root-agents-markdown");
+  });
+
+  it("does not let a custom page extension shadow an RSC route request", async () => {
+    const headers = createRscRequestHeaders();
+    const requestUrl = await createRscRequestUrl("/agents", headers);
+    const response = await fetch(`${baseUrl}${requestUrl}`, {
+      headers,
+    });
+    const body = await response.text();
+
+    expect(response.status).toBe(200);
+    expect(response.headers.get("content-type")).toBe("text/x-component");
+    expect(body).toContain("Agents route response");
+    expect(body).not.toContain("root-agents-markdown");
+  });
+
+  it("still serves routes discovered through a custom page extension", async () => {
+    const headers = createRscRequestHeaders();
+    const requestUrl = await createRscRequestUrl("/custom-extension", headers);
+    const response = await fetch(`${baseUrl}${requestUrl}`, {
+      headers,
+    });
+    const body = await response.text();
+
+    expect(response.status).toBe(200);
+    expect(response.headers.get("content-type")).toBe("text/x-component");
+    expect(body).toContain("Custom MDX route response");
+  });
+});
diff --git a/tests/fixtures/app-route-file-collision/agents.md b/tests/fixtures/app-route-file-collision/agents.md
new file mode 100644
index 0000000000..0f6501130f
--- /dev/null
+++ b/tests/fixtures/app-route-file-collision/agents.md
@@ -0,0 +1 @@
+# root-agents-markdown
diff --git a/tests/fixtures/app-route-file-collision/app/agents/page.tsx b/tests/fixtures/app-route-file-collision/app/agents/page.tsx
new file mode 100644
index 0000000000..f06fdbe7c6
--- /dev/null
+++ b/tests/fixtures/app-route-file-collision/app/agents/page.tsx
@@ -0,0 +1,3 @@
+export default function AgentsPage() {
+  return <h1>Agents route response</h1>;
+}
diff --git a/tests/fixtures/app-route-file-collision/app/custom-extension/page.mdx b/tests/fixtures/app-route-file-collision/app/custom-extension/page.mdx
new file mode 100644
index 0000000000..e6193af66c
--- /dev/null
+++ b/tests/fixtures/app-route-file-collision/app/custom-extension/page.mdx
@@ -0,0 +1 @@
+# Custom MDX route response
diff --git a/tests/fixtures/app-route-file-collision/app/layout.tsx b/tests/fixtures/app-route-file-collision/app/layout.tsx
new file mode 100644
index 0000000000..418716c35f
--- /dev/null
+++ b/tests/fixtures/app-route-file-collision/app/layout.tsx
@@ -0,0 +1,7 @@
+export default function RootLayout({ children }: { children: React.ReactNode }) {
+  return (
+    <html>
+      <body>{children}</body>
+    </html>
+  );
+}
diff --git a/tests/fixtures/app-route-file-collision/next.config.mjs b/tests/fixtures/app-route-file-collision/next.config.mjs
new file mode 100644
index 0000000000..f753933e92
--- /dev/null
+++ b/tests/fixtures/app-route-file-collision/next.config.mjs
@@ -0,0 +1,3 @@
+export default {
+  pageExtensions: ["tsx", "ts", "jsx", "js", "md", "mdx"],
+};
diff --git a/tests/page-extensions-resolve.test.ts b/tests/page-extensions-resolve.test.ts
index 621d05511a..b28861ebe8 100644
--- a/tests/page-extensions-resolve.test.ts
+++ b/tests/page-extensions-resolve.test.ts
@@ -11,81 +11,37 @@ import {
 // Ported in spirit from Next.js: test/e2e/app-dir/resolve-extensions/
 // https://github.com/vercel/next.js/blob/canary/test/e2e/app-dir/resolve-extensions/
 //
-// When users configure custom extensions via `pageExtensions` or
-// `turbopack.resolveExtensions` (e.g. `.platform.tsx`, `.mdx`, or `.png`), Vite must
-// know to attempt those extensions when resolving extensionless imports.
+// When users configure custom module extensions via `turbopack.resolveExtensions`
+// (e.g. `.web.tsx` or `.png`), Vite must know to attempt those extensions when
+// resolving extensionless imports.
 // Otherwise extensionless imports of files with those custom extensions
 // fail to resolve and the build crashes.
 //
 // Regression test for cloudflare/vinext#1502.
 describe("buildViteResolveExtensions", () => {
-  it("applies Next.js default pageExtensions priority when pageExtensions is undefined", () => {
-    // Even without a user-set pageExtensions, vinext normalises to the
-    // Next.js defaults `["tsx", "ts", "jsx", "js"]` and uses that order.
-    // `.cjs`/`.cts` trail the list so `vinext init`-renamed CJS configs
-    // (`tailwind.config.cjs`) resolve extensionlessly.
-    const extensions = buildViteResolveExtensions(undefined);
+  it("appends CJS config extensions to Vite defaults", () => {
+    const extensions = buildViteResolveExtensions();
     expect(extensions).toEqual([
-      ".tsx",
-      ".ts",
-      ".jsx",
-      ".js",
       ".mjs",
+      ".js",
       ".mts",
+      ".ts",
+      ".jsx",
+      ".tsx",
       ".json",
       ".cjs",
       ".cts",
     ]);
   });
 
-  it("returns the same list when pageExtensions matches the Next.js defaults", () => {
-    const extensions = buildViteResolveExtensions(["tsx", "ts", "jsx", "js"]);
-    expect(extensions).toEqual([
+  it("preserves configured Vite extensions and removes duplicates", () => {
+    expect(buildViteResolveExtensions([".web.tsx", ".tsx", ".cjs"])).toEqual([
+      ".web.tsx",
       ".tsx",
-      ".ts",
-      ".jsx",
-      ".js",
-      ".mjs",
-      ".mts",
-      ".json",
       ".cjs",
       ".cts",
     ]);
   });
-
-  it("prepends configured pageExtensions so user priority wins", () => {
-    // Next.js resolve-extensions fixture places `.web.tsx` before `.tsx`.
-    // The user's order must be preserved so `Component` resolves to
-    // `Component.web.tsx` before `Component.tsx`.
-    const extensions = buildViteResolveExtensions(["web.tsx", "tsx", "ts", "jsx", "js"]);
-    expect(extensions[0]).toBe(".web.tsx");
-    expect(extensions.indexOf(".web.tsx")).toBeLessThan(extensions.indexOf(".tsx"));
-  });
-
-  it("includes custom multi-segment extensions like .platform.tsx", () => {
-    // This is what made cloudflare/vinext#1502 surface: a user-configured
-    // multi-segment extension that Vite's defaults can't resolve.
-    const extensions = buildViteResolveExtensions(["platform.tsx", "tsx", "ts", "jsx", "js"]);
-    expect(extensions).toContain(".platform.tsx");
-    expect(extensions[0]).toBe(".platform.tsx");
-  });
-
-  it("includes .mdx when configured", () => {
-    const extensions = buildViteResolveExtensions(["tsx", "ts", "jsx", "js", "mdx"]);
-    expect(extensions).toContain(".mdx");
-  });
-
-  it("dedupes overlapping entries", () => {
-    const extensions = buildViteResolveExtensions(["tsx", "js"]);
-    expect(extensions.filter((e) => e === ".tsx").length).toBe(1);
-    expect(extensions.filter((e) => e === ".js").length).toBe(1);
-  });
-
-  it("strips leading dots and whitespace before normalising", () => {
-    const extensions = buildViteResolveExtensions([".platform.tsx", " tsx ", ""]);
-    expect(extensions[0]).toBe(".platform.tsx");
-    expect(extensions).toContain(".tsx");
-  });
 });
 
 describe("normalizeViteResolveExtensions", () => {
@@ -98,13 +54,8 @@ describe("normalizeViteResolveExtensions", () => {
   });
 });
 
-describe("vinext plugin wires pageExtensions into Vite resolve.extensions", () => {
-  it("forwards configured pageExtensions to config.resolve.extensions", async () => {
-    // Ported in spirit from Next.js: test/e2e/app-dir/resolve-extensions/
-    // The deploy suite failure surfaced when pageExtensions/resolveExtensions
-    // were configured beyond Vite's defaults — Vite couldn't resolve
-    // extensionless imports of files like `Component.platform.tsx`.
-    // Regression test for cloudflare/vinext#1502.
+describe("vinext plugin configures Vite resolve.extensions", () => {
+  it("keeps pageExtensions scoped to route discovery", async () => {
     const vinext = (await import("../packages/vinext/src/index.js")).default;
     const plugins = vinext();
     // oxlint-disable-next-line typescript/no-explicit-any
@@ -126,7 +77,7 @@ describe("vinext plugin wires pageExtensions into Vite resolve.extensions", () =
     );
     await fs.writeFile(
       path.join(tmpDir, "next.config.mjs"),
-      `export default { pageExtensions: ["platform.tsx", "tsx", "ts", "jsx", "js", "mdx"] };`,
+      `export default { pageExtensions: ["tsx", "ts", "jsx", "js", "md"] };`,
     );
 
     try {
@@ -137,16 +88,12 @@ describe("vinext plugin wires pageExtensions into Vite resolve.extensions", () =
       };
       // oxlint-disable-next-line typescript/no-explicit-any
       await (mainPlugin as any).config(mockConfig, { command: "build" });
-      const environmentConfig: any = { resolve: { extensions: [".earlier"] } };
+      const environmentConfig: any = { resolve: {} };
       (mainPlugin as any).configEnvironment("client", environmentConfig);
       const extensions: string[] = environmentConfig.resolve.extensions;
-      expect(extensions).toContain(".platform.tsx");
-      expect(extensions).toContain(".mdx");
+      expect(extensions).not.toContain(".md");
       expect(extensions).toContain(".tsx");
-      // User priority must win — `.platform.tsx` resolves before `.tsx`
-      // so a bare `./Component` import lands on `Component.platform.tsx`
-      // (mirrors Next.js / Turbopack resolveExtensions semantics).
-      expect(extensions.indexOf(".platform.tsx")).toBeLessThan(extensions.indexOf(".tsx"));
+      expect(extensions).toContain(".cjs");
     } finally {
       await fs.rm(tmpDir, { recursive: true, force: true }).catch(() => {});
     }

From a1cc5b6fbda53bc6123790b39c3803dadd9fb997 Mon Sep 17 00:00:00 2001
From: yyh <yuanyouhuilyz@gmail.com>
Date: Sat, 11 Jul 2026 22:18:36 +0800
Subject: [PATCH 2/2] fix(config): preserve default extension priority

---
 packages/vinext/src/routing/file-matcher.ts     | 17 +++++++++++++++--
 tests/app-router-route-file-collision.test.ts   | 16 ++++++++++++++++
 .../app/default-priority/Component.js           |  3 +++
 .../app/default-priority/Component.tsx          |  3 +++
 .../app/default-priority/page.tsx               |  9 +++++++++
 tests/page-extensions-resolve.test.ts           | 10 +++++-----
 6 files changed, 51 insertions(+), 7 deletions(-)
 create mode 100644 tests/fixtures/app-route-file-collision/app/default-priority/Component.js
 create mode 100644 tests/fixtures/app-route-file-collision/app/default-priority/Component.tsx
 create mode 100644 tests/fixtures/app-route-file-collision/app/default-priority/page.tsx

diff --git a/packages/vinext/src/routing/file-matcher.ts b/packages/vinext/src/routing/file-matcher.ts
index 81c5154356..f22b828450 100644
--- a/packages/vinext/src/routing/file-matcher.ts
+++ b/packages/vinext/src/routing/file-matcher.ts
@@ -4,6 +4,15 @@ import path, { toSlash } from "pathslash";
 import { escapeRegExp } from "../utils/regex.js";
 
 const DEFAULT_PAGE_EXTENSIONS = ["tsx", "ts", "jsx", "js"] as const;
+const DEFAULT_VINEXT_RESOLVE_EXTENSIONS = [
+  ".tsx",
+  ".ts",
+  ".jsx",
+  ".js",
+  ".mjs",
+  ".mts",
+  ".json",
+] as const;
 
 export function normalizePageExtensions(pageExtensions?: readonly string[] | null): string[] {
   if (!Array.isArray(pageExtensions) || pageExtensions.length === 0) {
@@ -110,18 +119,22 @@ export function findFileWithExts(
 }
 
 /**
- * Add the config extensions produced by `vinext init` to Vite's resolver.
+ * Add the config extensions produced by `vinext init` to vinext's resolver.
  *
  * `pageExtensions` is intentionally not part of module resolution. Next.js
  * uses it to discover route files; custom module extensions are configured
  * separately through `turbopack.resolveExtensions` or webpack
  * `resolve.extensions`.
  *
+ * The default order preserves vinext's existing module-resolution behavior
+ * and matches Next.js Turbopack for overlapping JavaScript and TypeScript
+ * extensions.
+ *
  * `.cjs`/`.cts` go last because `vinext init` renames CJS config files when it
  * adds `"type": "module"`, and app code may import those files extensionlessly.
  */
 export function buildViteResolveExtensions(
-  viteExtensions: readonly string[] = [".mjs", ".js", ".mts", ".ts", ".jsx", ".tsx", ".json"],
+  viteExtensions: readonly string[] = DEFAULT_VINEXT_RESOLVE_EXTENSIONS,
 ): string[] {
   const seen = new Set<string>();
   const result: string[] = [];
diff --git a/tests/app-router-route-file-collision.test.ts b/tests/app-router-route-file-collision.test.ts
index b63c9ebda2..1edf5287cb 100644
--- a/tests/app-router-route-file-collision.test.ts
+++ b/tests/app-router-route-file-collision.test.ts
@@ -61,4 +61,20 @@ describe("App Router route and project file collisions", () => {
     expect(response.headers.get("content-type")).toBe("text/x-component");
     expect(body).toContain("Custom MDX route response");
   });
+
+  it("preserves the default extensionless module resolution priority", async () => {
+    // Next.js Turbopack prefers .tsx over .js by default.
+    // https://github.com/vercel/next.js/blob/canary/turbopack/crates/turbopack-resolve/src/resolve.rs
+    const headers = createRscRequestHeaders();
+    const requestUrl = await createRscRequestUrl("/default-priority", headers);
+    const response = await fetch(`${baseUrl}${requestUrl}`, {
+      headers,
+    });
+    const body = await response.text();
+
+    expect(response.status).toBe(200);
+    expect(response.headers.get("content-type")).toBe("text/x-component");
+    expect(body).toContain("TypeScript module response");
+    expect(body).not.toContain("JavaScript module response");
+  });
 });
diff --git a/tests/fixtures/app-route-file-collision/app/default-priority/Component.js b/tests/fixtures/app-route-file-collision/app/default-priority/Component.js
new file mode 100644
index 0000000000..7e2c1e3ae0
--- /dev/null
+++ b/tests/fixtures/app-route-file-collision/app/default-priority/Component.js
@@ -0,0 +1,3 @@
+export default function Component() {
+  return "JavaScript module response";
+}
diff --git a/tests/fixtures/app-route-file-collision/app/default-priority/Component.tsx b/tests/fixtures/app-route-file-collision/app/default-priority/Component.tsx
new file mode 100644
index 0000000000..ff709d3f82
--- /dev/null
+++ b/tests/fixtures/app-route-file-collision/app/default-priority/Component.tsx
@@ -0,0 +1,3 @@
+export default function Component() {
+  return "TypeScript module response";
+}
diff --git a/tests/fixtures/app-route-file-collision/app/default-priority/page.tsx b/tests/fixtures/app-route-file-collision/app/default-priority/page.tsx
new file mode 100644
index 0000000000..9018117d8d
--- /dev/null
+++ b/tests/fixtures/app-route-file-collision/app/default-priority/page.tsx
@@ -0,0 +1,9 @@
+import Component from "./Component";
+
+export default function DefaultPriorityPage() {
+  return (
+    <h1>
+      <Component />
+    </h1>
+  );
+}
diff --git a/tests/page-extensions-resolve.test.ts b/tests/page-extensions-resolve.test.ts
index b28861ebe8..5353c0d4d2 100644
--- a/tests/page-extensions-resolve.test.ts
+++ b/tests/page-extensions-resolve.test.ts
@@ -19,15 +19,15 @@ import {
 //
 // Regression test for cloudflare/vinext#1502.
 describe("buildViteResolveExtensions", () => {
-  it("appends CJS config extensions to Vite defaults", () => {
+  it("appends CJS config extensions to vinext defaults", () => {
     const extensions = buildViteResolveExtensions();
     expect(extensions).toEqual([
-      ".mjs",
-      ".js",
-      ".mts",
+      ".tsx",
       ".ts",
       ".jsx",
-      ".tsx",
+      ".js",
+      ".mjs",
+      ".mts",
       ".json",
       ".cjs",
       ".cts",