Optional Json doesn't work in axum 0.8.1

[robert-sjoblom]

Summary

Ran into an issue while moving from 0.7 to 0.8. The first breaking change was the url -- fixed that, ran into another that I can't seem to find an answer to:

the trait bound `fn(axum::extract::State<config::Config>, axum::extract::Path<(std::string::String, std::string::String)>, std::option::Option<axum::Json<Request>>) -> impl std::future::Future<Output = std::result::Result<axum::Json<CreateResponse>, (axum::http::StatusCode, axum::Json<ErrorResponse>)>> {create_db}: axum::handler::Handler<_, _>` is not satisfied

Okay, let's use the debug handler macro to see what that actually means:

-axum = { version = "0.8.0", features = ["json"] }
+axum = { version = "0.8.1", features = ["json", "macros"] }
+axum-macros = { version = "0.5.0-rc.1" }

Use the macro:

+#[axum::debug_handler]
 async fn create_db(
     State(config): State<Config>,
     Path((_env, service_name)): Path<(String, String)>,
     request: Option<Json<Request>>,
 ) -> Result<Json<CreateResponse>, (StatusCode, Json<ErrorResponse>)> {

Oh:

the trait bound `std::option::Option<axum::Json<Request>>: axum::extract::FromRequest<config::Config, _>` is not satisfied
Function argument is not a valid axum extractor. 

Hm. I guess this is the relevant part?

breaking:: Option<T> as an extractor now requires T to implement the new trait OptionalFromRequest (if used as the last extractor) or OptionalFromRequestParts (other extractors) (https://github.com/tokio-rs/axum/pull/2475)

Is it a bug?

axum version

0.8.1

[mladedav]

This has been since added and will work in next releases although a little differently. Previously this returned None for example when there was different Content-Type or if the json itself was malformed, this will now error out and just empty bodies without declared content type will return None.

If you want the old behavior and for now you can use Result<Json<T>, _>.

[jplatte]

Note that #3142 has not been released yet.