error on "base path" with "server build path" collision

adding special configurations

packages/integrations/cloudflare/README.md

@@ -107,6 +107,12 @@ export function get({ params }) {
 }
 ```
 
+## Headers, Redirects and function invocation routes
+
+Cloudflare has support for adding custom [headers](https://developers.cloudflare.com/pages/platform/headers/), configuring static [redirects](https://developers.cloudflare.com/pages/platform/redirects/) and defining which routes should [invoke functions](https://developers.cloudflare.com/pages/platform/functions/function-invocation-routes/). This is handled via the special files called _headers, _redirects and _routes.json which can be placed in the `public` folder to take effect.
+
+The _routes.json file is generated during build to prevent a function invocation on assets paths. This will be overwritten when a custom _routes.json is provided. If that is the case the static files will still be served, but the request will go through a function invocation and will count against the request limits of your Cloudflare plan.
+
 ## Troubleshooting
 
 For help, check out the `#support` channel on [Discord](https://astro.build/chat). Our friendly Support Squad members are here to help!

packages/integrations/cloudflare/src/index.ts

@@ -33,6 +33,8 @@ const SHIM = `globalThis.process = {
 	env: {},
 };`;
 
+const SERVER_BUILD_FOLDER = '/$server_build/';
+
 export default function createIntegration(args?: Options): AstroIntegration {
 	let _config: AstroConfig;
 	let _buildConfig: BuildConfig;
@@ -47,7 +49,7 @@ export default function createIntegration(args?: Options): AstroIntegration {
 				updateConfig({
 					build: {
 						client: new URL(`.${config.base}`, config.outDir),
-						server: new URL('./server/', config.outDir),
+						server: new URL(`.${SERVER_BUILD_FOLDER}`, config.outDir),
 						serverEntry: '_worker.js',
 					},
 				});
@@ -63,6 +65,11 @@ export default function createIntegration(args?: Options): AstroIntegration {
 
 `);
 				}
+
+				if (config.base === SERVER_BUILD_FOLDER) {
+					throw new Error(`
+  [@astrojs/cloudflare] \`base: "${SERVER_BUILD_FOLDER}"\` is not allowed. Please change your \`base\` config to something else.`);
+				}
 			},
 			'astro:build:setup': ({ vite, target }) => {
 				if (target === 'server') {
@@ -86,7 +93,7 @@ export default function createIntegration(args?: Options): AstroIntegration {
 				// Backwards compat
 				if (needsBuildConfig) {
 					buildConfig.client = new URL(`.${_config.base}`, _config.outDir);
-					buildConfig.server = new URL('./server/', _config.outDir);
+					buildConfig.server = new URL(`.${SERVER_BUILD_FOLDER}`, _config.outDir);
 					buildConfig.serverEntry = '_worker.js';
 				}
 			},