Describe the problem

The handling of error responses from page endpoints is currently a bit confusing and unflexible.

If a GET page endpoint returns a 4xx or 5xx response, then any props returned in its body are ignored and the nearest __error.svelte page is rendered. If body is an Error instance, then this (along with its enumerable properties) are available to that page.

If a non-GET page endpoint returns a 4xx or 5xx response, then any props returned in its body argument are passed to the regular (non-error) page, merged with the GET page endpoint body props, if any. If body is an Error instance, then (I believe) the nearest __error.svelte page is rendered instead and is sent this error.

Describe the proposed solution

I think it would be nice, whether the user is on a GET or non-GET endpoint, to use the response from the body - whether it's a POJO or an Error - to determine whether to render the regular page or the nearest __error.svelte page, respectively.

I'm not sure what other fallout of this might be.

I'm not sure what we want to do if a page endpoint returns a 4xx/5xx status but no body at all. Create a new Error() whose message is the appropriate description for that HTTP status code?

Alternatives considered

No response

Importance

would make my life easier

Additional Information

No response