Vercel adapter default changes (#8239)

* Vercel adapter default changes

* Update .changeset/silly-dolphins-try.md

Co-authored-by: Sarah Rainsberger <sarah@rainsberger.ca>

* Fix tests

* chore: correctly export `pageModule` when using `functionPerRoute`

* Update .changeset/silly-dolphins-try.md

Co-authored-by: Emanuele Stoppa <my.burning@gmail.com>

* Update .changeset/silly-dolphins-try.md

Co-authored-by: Emanuele Stoppa <my.burning@gmail.com>

* Make throw be the entrypoint

---------

Co-authored-by: Sarah Rainsberger <sarah@rainsberger.ca>
Co-authored-by: Emanuele Stoppa <my.burning@gmail.com>

8 files changed, 39 insertions, 8 deletions

diff --git a/.changeset/silly-dolphins-try.md b/.changeset/silly-dolphins-try.md
new file mode 100644
index 000000000..dcd15130d
--- /dev/null
+++ b/.changeset/silly-dolphins-try.md
@@ -0,0 +1,9 @@
+---
+'@astrojs/vercel': major
+---
+
+Vercel adapter now defaults to `functionPerRoute`.
+
+With this change, `@astrojs/vercel/serverless` now splits each route into its own function. By doing this, the size of each function is reduced and startup time is faster.
+
+You can disable this option, which will cause the code to be bundled into a single function, by setting `functionPerRoute` to `false`.
diff --git a/packages/astro/src/core/build/generate.ts b/packages/astro/src/core/build/generate.ts
index 0a3d80000..53a350342 100644
--- a/packages/astro/src/core/build/generate.ts
+++ b/packages/astro/src/core/build/generate.ts
@@ -163,7 +163,7 @@ export async function generatePages(opts: StaticBuildOptions, internals: BuildIn
 					opts.settings.adapter?.adapterFeatures?.functionPerRoute
 				) {
 					// forcing to use undefined, so we fail in an expected way if the module is not even there.
-					const ssrEntry = ssrEntryPage?.manifest?.pageModule;
+					const ssrEntry = ssrEntryPage?.pageModule;
 					if (ssrEntry) {
 						await generatePage(pageData, ssrEntry, builtPaths, pipeline);
 					} else {
diff --git a/packages/astro/src/core/build/plugins/plugin-ssr.ts b/packages/astro/src/core/build/plugins/plugin-ssr.ts
index 8650d5870..44fc31155 100644
--- a/packages/astro/src/core/build/plugins/plugin-ssr.ts
+++ b/packages/astro/src/core/build/plugins/plugin-ssr.ts
@@ -178,6 +178,8 @@ function vitePluginSSRSplit(
 				imports.push(...ssrCode.imports);
 				contents.push(...ssrCode.contents);
 
+				exports.push('export { pageModule }');
+
 				return `${imports.join('\n')}${contents.join('\n')}${exports.join('\n')}`;
 			}
 			return void 0;
diff --git a/packages/integrations/vercel/README.md b/packages/integrations/vercel/README.md
index b01a7c716..e16d98390 100644
--- a/packages/integrations/vercel/README.md
+++ b/packages/integrations/vercel/README.md
@@ -210,9 +210,11 @@ export default defineConfig({
 });
 ```
 
-### Per-page functions
+### Function bundling configuration
 
-The Vercel adapter builds to a single function by default. Astro 2.7 added support for splitting your build into separate entry points per page. If you use this configuration the Vercel adapter will generate a separate function for each page. This can help reduce the size of each function so they are only bundling code used on that page.
+The Vercel adapter splits builds into a separate function per route by default. This helps reduce the size of each function, as it only bundles code used on that page.
+
+You can disable this and build to a single function by setting the `functionPerRoute` configuration option to `false`:
 
 ```js
 // astro.config.mjs
@@ -222,7 +224,7 @@ import vercel from '@astrojs/vercel/serverless';
 export default defineConfig({
   output: 'server',
   adapter: vercel({
-    functionPerRoute: true,
+    functionPerRoute: false,
   }),
 });
 ```
diff --git a/packages/integrations/vercel/package.json b/packages/integrations/vercel/package.json
index fc622776c..726f6f9d4 100644
--- a/packages/integrations/vercel/package.json
+++ b/packages/integrations/vercel/package.json
@@ -17,8 +17,8 @@
   "bugs": "https://github.com/withastro/astro/issues",
   "homepage": "https://docs.astro.build/en/guides/integrations-guide/vercel/",
   "exports": {
-    "./edge": "./dist/edge/adapter.js",
-    "./edge/entrypoint": "./dist/edge/entrypoint.js",
+    "./edge": "./dist/edge/throw.js",
+    "./edge/entrypoint": "./dist/edge/throw.js",
     "./serverless": "./dist/serverless/adapter.js",
     "./serverless/entrypoint": "./dist/serverless/entrypoint.js",
     "./static": "./dist/static/adapter.js",
diff --git a/packages/integrations/vercel/src/edge/throw.ts b/packages/integrations/vercel/src/edge/throw.ts
new file mode 100644
index 000000000..5041370e0
--- /dev/null
+++ b/packages/integrations/vercel/src/edge/throw.ts
@@ -0,0 +1,18 @@
+const msg = `
+The Astro Vercel Edge adapter has been removed. We recommend switching to @astrojs/vercel/serverless and enabling Edge middleware.
+
+import { defineConfig } from 'astro/config';
+import vercel from '@astrojs/vercel/serverless';
+
+export default defineConfig({
+	output: 'server',
+	adapter: vercel({
+		edgeMiddleware: true,
+	})
+})
+`.trim();
+
+throw new Error(msg);
+
+// Make sure bundlers treat this as ESM.
+export default {};
diff --git a/packages/integrations/vercel/src/serverless/adapter.ts b/packages/integrations/vercel/src/serverless/adapter.ts
index d5ac9c881..0bfdd31f7 100644
--- a/packages/integrations/vercel/src/serverless/adapter.ts
+++ b/packages/integrations/vercel/src/serverless/adapter.ts
@@ -68,7 +68,7 @@ export default function vercelServerless({
 	analytics,
 	imageService,
 	imagesConfig,
-	functionPerRoute = false,
+	functionPerRoute = true,
 	edgeMiddleware = false,
 }: VercelServerlessConfig = {}): AstroIntegration {
 	let _config: AstroConfig;
diff --git a/packages/integrations/vercel/test/fixtures/serverless-prerender/astro.config.mjs b/packages/integrations/vercel/test/fixtures/serverless-prerender/astro.config.mjs
index 84b96c27d..f5a86e609 100644
--- a/packages/integrations/vercel/test/fixtures/serverless-prerender/astro.config.mjs
+++ b/packages/integrations/vercel/test/fixtures/serverless-prerender/astro.config.mjs
@@ -4,7 +4,7 @@ import vercel from '@astrojs/vercel/serverless';
 export default defineConfig({
 	adapter: vercel({
 		// Pass some value to make sure it doesn't error out
-		includeFiles: ['included.js']
+		includeFiles: ['included.js'],
 	}),
 	output: 'server'
 });