feat: revert back to the .js config

cli/src/helpers/createProject.ts

@@ -64,8 +64,8 @@ export const createProject = async ({
   if (appRouter) {
     // Replace next.config
     fs.copyFileSync(
-      path.join(PKG_ROOT, "template/extras/config/next-config-appdir.ts"),
-      path.join(projectDir, "next.config.ts")
+      path.join(PKG_ROOT, "template/extras/config/next-config-appdir.js"),
+      path.join(projectDir, "next.config.js")
     );
 
     selectLayoutFile({ projectDir, packages });

cli/src/installers/envVars.ts

@@ -44,7 +44,7 @@ export const envVariablesInstaller: Installer = ({
       "template/extras/src/env",
       envFile
     );
-    const envSchemaDest = path.join(projectDir, "src/env.ts");
+    const envSchemaDest = path.join(projectDir, "src/env.js");
     fs.copyFileSync(envSchemaSrc, envSchemaDest);
   }
 
@@ -63,7 +63,7 @@ const getEnvContent = (
   scopedAppName: string
 ) => {
   let content = `
-# When adding additional environment variables, the schema in "/src/env.ts"
+# When adding additional environment variables, the schema in "/src/env.js"
 # should be updated accordingly.
 `
     .trim()

cli/template/base/next.config.ts → cli/template/base/next.config.js

@@ -1,18 +1,23 @@
-import { type NextConfig } from "next";
-
 /**
  * Run `build` or `dev` with `SKIP_ENV_VALIDATION` to skip env validation. This is especially useful
  * for Docker builds.
  */
-import "./src/env";
+await import("./src/env.js");
 
+/** @type {import("next").NextConfig} */
 const config = {
   reactStrictMode: true,
+
+  /**
+   * If you are using `appDir` then you must comment the below `i18n` config out.
+   *
+   * @see https://github.com/vercel/next.js/issues/41980
+   */
   i18n: {
     locales: ["en"],
     defaultLocale: "en",
   },
   transpilePackages: ["geist"],
-} satisfies NextConfig;
+};
 
 export default config;

cli/template/extras/config/next-config-appdir.ts → cli/template/extras/config/next-config-appdir.js

@@ -1,11 +1,10 @@
-import { type NextConfig } from "next";
-
 /**
  * Run `build` or `dev` with `SKIP_ENV_VALIDATION` to skip env validation. This is especially useful
  * for Docker builds.
  */
-import "./src/env";
+await import("./src/env.js");
 
-const config = {} satisfies NextConfig;
+/** @type {import("next").NextConfig} */
+const config = {};
 
 export default config;