Vercel adapter: parameter "functionPerRoute" generate serverless function even for prerendered routes

[bentouch-digital]

Astro Info

Astro                    v4.4.2
Node                     v20.10.0
System                   macOS (arm64)
Package Manager          yarn
Output                   hybrid
Adapter                  @astrojs/vercel/serverless
Integrations             @astrojs/tailwind
                         astro-icon
                         @astrojs/vue
                         @storyblok/astro
                         extract-tailwind-classes
                         redirections

If this issue only occurs in one browser, which browser is a problem?

All

Describe the Bug

Actually, when I build the projet with the Vercel adapter and the parameter functionPerRoute to true, it generates serverless functions for all routes, prerendered ones too. I have a route named [...slug].astro that generates only prerendered pages. But with this configuration it generates a serverless function [...slug].astro, as the result, all 404 errors fallback on this serverless function and a response is returned with code 200. If i set functionPerRouteto false, it's works as intended.

What's the expected result?

Must not generate serverless functions for prerendered pages.

Link to Minimal Reproducible Example

https://stackblitz.com/edit/github-9beo4b

Participation

• I am willing to submit a pull request for this issue.

[matthewp]

Your example doesn't have prerendered pages. Please update the example to match the problem you're describing.

[github-actions]

Hello @bentouch-digital. Please provide a minimal reproduction using a GitHub repository or StackBlitz. Issues marked with needs repro will be closed if they have no activity within 3 days.

[dylanalizon]

Your example doesn't have prerendered pages. Please update the example to match the problem you're describing.

@matthewp Hello, the ouput is "hybrid", unless I'm mistaken all pages are prerendered by default, so the index.astro is a prerendered one.

[lilnasy]

Good first issue!

This is an opportunity for astro users to learn about how astro works by fixing a small but real bug. You can expect to get help setting up the dev environment, and understanding the project structure in #dev channel of our discord server (https://astro.build/chat).

What's the bug?

The functionPerRoute config creates more functions than necessary.

What's going wrong here?

Adapters depend on Astro's Integration API to provide them with the routes to make functions out of. The routes are provided in a map called entrypoints.

Neither Astro nor the vercel adapter make a distinction between prerendered and on-demand rendered routes - all are turned into functions. Only non-prerendered routes should be exposed to the adapter.

Where do I start looking?

The part where Astro's internals pass the entrypoints map to the adapter is here:

astro/packages/astro/src/core/build/plugins/plugin-manifest.ts

Lines 98 to 106 in eb8bffe

	await runHookBuildSsr({
	config: options.settings.config,
	manifest,
	logger: options.logger,
	entryPoints: internals.entryPoints,
	middlewareEntryPoint: shouldPassMiddlewareEntryPoint
	? internals.middlewareEntryPoint
	: undefined,
	});

The part where Astro's internals populate the entrypoints map in the first place is here:

astro/packages/astro/src/core/build/plugins/plugin-ssr.ts

Lines 201 to 206 in eb8bffe

	for (const moduleKey of Object.keys(chunk.modules)) {
	if (moduleKey.startsWith(RESOLVED_SPLIT_MODULE_ID)) {
	internals.ssrSplitEntryChunks.set(moduleKey, chunk);
	storeEntryPoint(moduleKey, options, internals, chunk.fileName);
	}
	}

[mingjunlu]

@lilnasy Thanks for providing guidance on this issue! I would like to give it a try 🙂