fix(routing): emit error for forbidden rewrite

[ematipico]

Changes

Closes PLT-2607
Closes #12336

Even though the issue was reported for Astro v4, unfortunately, we can't fix it because the prerender field doesn't change there, and we fixed that issue in v5.

This PR forbids to rewrite a SSR route with a SSG route, when using the server output. That's because when the SSG routes are built, they aren't part of the server output, and they are emitted as static files. Static files are served by the host, and the Astro runtime can't retrieve them at runtime during the rewriting process. This results in a runtime error at the moment.

Because of that, I decided to simulate a similar behaviour and throw an error, with some information.

Testing

I added a new test case

Docs

I will probably send a PR to explain this limitation.

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[sarah11918]

Question: does this happen only with 'server' configured, or for any on-demand page that tries to rewrite with a prerendered page?

With the new 'static' mode, someone could still add an adapter and have an on-demand route that attempts a rewrite to a (default) prerendered page. Is that also a problem?

[lilnasy]

Couldn't it just be supported instead of being forbidden?
For example, Cloudflare provides a simple function to retrieve static assets.: https://developers.cloudflare.com/workers/static-assets/binding/. Similarly for node, it's a matter of reading from disk.

[ematipico]

Couldn't it just be supported instead of being forbidden? For example, Cloudflare provides a simple function to retrieve static assets.: developers.cloudflare.com/workers/static-assets/binding. Similarly for node, it's a matter of reading from disk.

Not at this time, because as you said it's the adapter that helps with that (Cloudflare and Node.js), but the rewrite code is runtime agnostic, so we can't easily implement this as bugfix without providing an adapter feature for this use case.

We can definitely support this via adapters, with some architectural changes, but that's definitely a feature, and it requires adapters to have a role in this.

[ematipico]

Question: does this happen only with 'server' configured, or for any on-demand page that tries to rewrite with a prerendered page?

With the new 'static' mode, someone could still add an adapter and have an on-demand route that attempts a rewrite to a (default) prerendered page. Is that also a problem?

@sarah11918 I am not really sure to be honest, I need to investigate

[sarah11918]

Just a note that I'll want to look over docs after we know whether we need to specifically say 'server' mode, or whether this is the case for any on-demand rendered route, even in the new 'static' mode!

[ematipico]

@sarah11918 I looked at it, and this change affects only server adapters.

[sarah11918]

Thanks @ematipico ! Had just wanted to make sure we needed the extra bit of wording (and that everything is fine in static mode) to know exactly what we needed to say! 🙌

Just fixed some tiny typos and had a thought about the error name for your consideration!

[sarah11918]

Suggested change

	title: "Can't use `Astro.rewrite()` from a on-demand route to static route with 'server' output.",
	title: "Can't use `Astro.rewrite()` from an on-demand route to static route with 'server' output.",

typo fix here at the very least, but in fact, see suggestion for title below also.

[sarah11918]

Just noting that there may eventually be other kinds of "forbidden" rewrites, so not sure whether you want to add more context like ForbiddenRewriteToStatic or something like that?

[sarah11918]

At the very least, the typo needs to be corrected to an on-demand route.

Also noting that this is a little longer than other titles are, and almost repeats the docs text exactly. So this could instead be a shorter thing like:

Forbidden rewrite to a static route

and then let the docs text explain what's happening?

[sarah11918]

Suggested change

	`You tried to rewrite the on-demand route '${from}' with the static route '${to}', when using the 'server' output. \n\nThe static route '${to}' is rendered by the component
	'${component}', which is marked as prerendered. This is a forbidden operation because during the build the component '${component}' is compiled to an
	HTML file, which is can't be retrieved at runtime by Astro.`,
	`You tried to rewrite the on-demand route '${from}' with the static route '${to}', when using the 'server' output. \n\nThe static route '${to}' is rendered by the component
	'${component}', which is marked as prerendered. This is a forbidden operation because during the build the component '${component}' is compiled to an
	HTML file, which can't be retrieved at runtime by Astro.`,

[sarah11918]

Suggested change

	* `Astro.rewrite()` can't be used to rewrite an on-demand route with a static route, when using the `"server"` output.
	* `Astro.rewrite()` can't be used to rewrite an on-demand route with a static route when using the `"server"` output.

[sarah11918]

Suggested change

	Now Astro emits an error when `Astro.rewrite` is used to rewrite an on-demand route with a static route, when using the `"server"` output.
	This isn't possible because Astro can't retrieve the emitted static route at runtime, because it's served by the hosting platform, and not Astro itself.
	Adds an error when `Astro.rewrite()` is used to rewrite an on-demand route with a static route when using the `"server"` output.
	This is a forbidden rewrite because Astro can't retrieve the emitted static route at runtime. This route is served by the hosting platform, and not Astro itself.