Build fails using server islands and static output mode

[JannikWempe]

Astro Info

Astro                    v5.1.3
Node                     v18.20.3
System                   Linux (x64)
Package Manager          npm
Output                   static
Adapter                  @astrojs/vercel
Integrations             none

Describe the Bug

Rendering a server island (adding server:defer to any component), using adapter vercel (can also reproduce it with sst) and output: "static" results in this error:

[NoAdapterInstalledServerIslands]

It works fine with the netlify adapter though.

---

This is a discussion about the issue on Discord with @louisescher.

What's the expected result?

The build should work using server islands and a static output mode. (It does using the netlify adapter.)

Link to Minimal Reproducible Example

https://stackblitz.com/edit/github-s2hf8p8k

Participation

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

[AirBorne04]

Not sure what the implications of this is, but i have found the following.

• Cloudflare adapter works
• the error message depends on the buildOutput returned from the adapter like here

  adapters/packages/vercel/src/index.ts

  Line 89 in 83cedad

  buildOutput,

  and needs to be server in order to work as expected
• vercel specifies static or server as output (making it the same as the output)

switching the buildSetting to server on the vercel adapter makes the error go away, but i am not sure about other implications.

[JannikWempe]

Not sure what the implications of this is

I know one implication (because it was the reason I discovered this).

I wanted to cache a server island using cache headers. That did not work because the p param of the generated path from where the data for that island is fetched changes on each request. p contains the encrypted props of that island. My props were static, but p changes on each request, which causes cache misses. p changes because encrypting is done using a random iv (see here).

Server output causes p to change in each request. Only static output will cause a stable p and therefore cachable server island.

TLDR; You can't cache server islands.

That is why it is not an option to just use server output.

[AirBorne04]

Hi @JannikWempe

I got the issue, I verified that the output is as expected when changing the adapter options, small fix that should do. Can you also check if this is the fix you were looking for?

[JannikWempe]

Hey @AirBorne04 thanks for working on a fix.

I was able to build the project locally with output: "static" using your changes. I didn't manage to deploy it to Vercel though (seeing 404). But that may be just my incompetence 😅 I did run astro build and tried to deploy my prebuilt files directly with vercel deploy --prebuilt.

[AirBorne04]

Hi @JannikWempe

I did a little more digging and hit some issues but also came to a possible easy solution.

When we set output="static" the adapter builds different than output="server". From what I do understand is that we actually have two steps in building the astro project with an adapter. In a simplified way it is step one building the Astro Project that can be ("static" | "server") than we do have the adapter (like layout the files to fit a certain deployment environment) which by its nature is always for a server/runtime.

Therefore I would think that the adapter always should build in "server" config, I tried settings this but for some (currently unknown to me) reason that does not result in the correct build (call to _server_island fails) while doing the same with output="server"works. I need to dig a little deeper what the issue is here.

But what I found that setting export const prerender = true for the index.astro has the effect wanted. Maybe you can give this a try.

I think that should generally be the way to go, since this is more of a Astro project concern how the files are build, not what the layout for the runtime should be.

[JannikWempe]

Adding export const prerender = true does indeed work as expected 👍🏼

With this, using output: "server" doesn't seem to be an issue.

It is inconsistent though, that some adapters behave differently, for example:

• vercel would need output: "server" and export const prerender = true on the route
• netlify would only need output: "static" (no export const prerender = true needed)

[AirBorne04]

I agree that they should behave the same. In my opinion they should be considered server (edge or non edge) so basically ignoring this setting altogether unless I am missing something and ultimately work like the netlify adapter already does. In the vercel adapter the static and server config from the project would influence the output which I think is wrong. If the adapter has the need for a config it should be configured on the adapter not on the Astro project.
So I will check what I can tweak to make the adapter work that way 👍

[JannikWempe]

Thanks a ton, @AirBorne04 👍🏼

I think this issue can be closed.

Finding a consistent, minimal confusing way to handle inconsistencies seems to be a separate thing. (Feel free to reopen if you disagree.)