Prerendering overhaul

[Rich-Harris]

Migration

General

+server pages can be prerendered, too now, by adding the export const prerender = .. option to them. By default they are not prerendered, but any +server page that is referenced from a prerendered page inherits the prerender option of that page unless explicitly set otherwise. This might lead to a situation where you now get a "Cannot prerender a +server file with POST, PATCH, PUT, or DELETE" error. To fix it, add export const prerender = false; to the +server file where it happens, or move the mutative methods in a different file.

adapter-static

Instead of only checking the default for prerendering, the actual found routes are now checked for prerendering. If one of them is not prerenderable, an error is thrown unless you set the fallback option. If you get this error now, adjust your code so that

• either the non-prerenderable routes are not crawled anymore
• or the non-prerenderable routes are made prerenderable
• or set the fallback option

PR description

#6356.

• differentiate between prerenderable and non-prerenderable endpoints
• exclude routes with prerender = true from generated manifests
• allow 'auto' (prerender, but also include in manifests) as a value, alongside true (only prerender, exclude from manifests) and false (never prerender, include in manifests)
• throw in adapter-static if any routes are prerender = false or prerender = 'auto' (or unknown, in the case of endpoints that are never fetched during prerendering)
• docs
• idk, probably some tests and stuff

Not in scope for this PR: removing config.kit.prerender.default and using defaults from +layout[.server].js files. That can be added to #6197 once this is merged.

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Tests

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🦋 Changeset detected

Latest commit: 64a4c75

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@sveltejs/adapter-static	Patch
@sveltejs/kit	Patch

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[benmccann]

should we add JS here to clarify that you can't add it to +page.svelte?

Suggested change

	Prerendering happens automatically for any `+page` or `+server` file with the `prerender` annotation:
	Prerendering happens automatically for any `+page` or `+server` JS file with the `prerender` annotation:

[Rich-Harris]

I was hoping the code sample would make it clear — adding JS muddies the waters a bit in the case where people are using TypeScript

[dummdidumm]

There are some other places where it's +page/layout with the .js ending. We should probably make that consistent, either adding the .js file always or never (except for when we introduce it).

[benmccann]

now that I've seen the docs and understand what this option does, I'll throw another name into the ring. how about 'partial'?

[Rich-Harris]

I think I prefer auto — partial doesn't have the right connotation to me, it sounds like the page is being partially prerendered

[dummdidumm]

Looks good! Will adjust the minor suggestions I made myself and merge to get the related PR in good state

[dummdidumm]

I was confused for a bit because I think "what kind of folder names are these?". Maybe instead +page.js, or +page.server.js, or +server.js?

[dummdidumm]

Skipping this for now, seing that it's like this for all others as well.

[dummdidumm]

It took me a little while to understand why this works - why can I prerender AND SSR a route - until I thought "oh yes with [slug]". I don't know how to express this better, but maybe we can come up with something later.