Add ServeDir::fallback

[davidpdrsn]

Fixes #240

Example usage:

let service = ServeDir::new("assets")
    // respond with `index.html` for missing files
    .fallback(ServeFile::new("assets/index.html"));

This will call ServeFile if the file is missing.

You can also achieve this using combinators from tower::ServiceExt but several have asked for this so probably makes sense to add.

Note this is different from axum_extra::routing::SpaRouter which requires assets to be nested (for example under /assets/*). This doesn't require that and thus allows serving assets at the top level (i.e. GET /style.css or smth like that).

TODO

• Fix remaining todos in the code
• Make sure its compatible with axum
• Think about setting status codes for fallback responses
• Changelog

[jplatte]

This also allows showing a custom 404 page for a ServeDir, right? I think that really calls for a convenience API to override ServeFiles success status code.

[jplatte]

Oops

[davidpdrsn]

This also allows showing a custom 404 page for a ServeDir, right?

Yep it does!

I think that really calls for a convenience API to override ServeFiles success status code.

Hm what do you mean? Like not responding with 200 Ok if the file is found and served?

[davidpdrsn]

hehe not quite ready for review yet :P

[jplatte]

Misclicked in mobile UI, not sure how to change back 😅

Edit: Ah you did already.

[davidpdrsn]

I've fixed it :)

[jplatte]

I think that really calls for a convenience API to override ServeFiles success status code.

Hm what do you mean? Like not responding with 200 Ok if the file is found and served?

Yeah, since you'd want the custom not-found page to still have the 404 status code even when served from an on-disk file successfully.

[davidpdrsn]

Ahh I see. So like .fallback(ServeFile::new("not_found.html").success_status(StatusCode::NOT_FOUND)) or something along those lines 🤔 Have to think about this.

[davidpdrsn]

Maybe

ServeDir::new("...").fallback_with_status(ServeFile::new("not_found.html"), StatusCode::NOT_FOUND)

That way we wouldn't need anything new in ServeFile, or whatever other service you might be using 🤔

[jplatte]

Maybe

ServeDir::new("...").fallback_with_status(ServeFile::new("not_found.html"), StatusCode::NOT_FOUND)

That way we wouldn't need anything new in ServeFile, or whatever other service you might be using 🤔

I guess the question there would be when do you apply the custom status code? Probably if the status code from the inner service is anything 2xx?

Also, if this is not attached to ServeFile, it should probably be its own service adapter, and then maybe instead of .fallback_with_status(inner_svc, status_code) as an alias for .fallback(inner_svc.layer(SetStatus::layer(status_code)) we should have .not_found_service(inner_svc) as an alias for .fallback(inner_svc.layer(SetStatus::layer(StatusCode::NOT_FOUND))? That would provide full flexibility using the adapter, and a very succinct helper method for the common use case.

[davidpdrsn]

I'll try and find some time to work on this soon but might just make a breaking release next week to get #237 out regardless if this has landed or not.

[davidpdrsn]

Made a PR to add a SetStatus middleware #248. When that is merged I'll update this to include helpers that also set the status from the fallback to 404. Once thats done I think we can merge this!

I don't think a more general fallback mechanism is possible since it requires cloning the request (to call the fallback). ServeDir and ServeFile doesn't have that issue since they don't require the body or extensions so they're a special case.

[davidpdrsn]

These new type params makes this a breaking change.

[davidpdrsn]

This is finally ready for review!

[jplatte]

All methods that are reasonable for asset routes don't have a body anyways, right? By the way, does ServeDir still serve files for non-GET requests? I think it did that at some point.

[davidpdrsn]

All methods that are reasonable for asset routes don't have a body anyways, right?

Yes. At least I can't think of a use case for serving a static file and having a request body.

By the way, does ServeDir still serve files for non-GET requests? I think it did that at some point.

It still accepts all methods. Perhaps we should change that to respond with 405 for non-GET requests.

[jplatte]

There is proper handling of HEAD now, right? That should probably stay. Not sure about OPTIONS, probably okay to have it return 405 if the user doesn't have a cors middleware set up.

[jplatte]

Apart from latest comments, looks good!