debug_handler with two state types?

[damccull]

Summary

When I include axum_flash::Flash in my handler's parameters, the code works fine and I can both get and return the flash. However, when I add #[axum::debug_handler] macro to the handler containing this parameter, I get this error:

 1  error[E0277]: the trait bound `axum_flash::Config: FromRef<Pool<Sqlite>>` is not satisfied
   --> src/routes/learning_portal/quiz.rs:76:12
    |
 76 |     flash: Flash,
    |            ^^^^^ the trait `FromRef<Pool<Sqlite>>` is not implemented for `axum_flash::Config`
    |
    = help: the trait `FromRef<Pool<Sqlite>>` is not implemented for `axum_flash::Config`
            but trait `FromRef<AppState>` is implemented for it
    = help: for that trait implementation, expected `AppState`, found `Pool<Sqlite>`
    = note: required for `Flash` to implement `FromRequestParts<Pool<Sqlite>>`
    = help: see issue #48214

 2  error[E0277]: the trait bound `axum_flash::Config: FromRef<Pool<Sqlite>>` is not satisfied
   --> src/routes/learning_portal/quiz.rs:76:12
    |
 76 |     flash: Flash,
    |            ^^^^^ the trait `FromRef<Pool<Sqlite>>` is not implemented for `axum_flash::Config`
    |
    = help: the trait `FromRef<Pool<Sqlite>>` is not implemented for `axum_flash::Config`
            but trait `FromRef<AppState>` is implemented for it
    = help: for that trait implementation, expected `AppState`, found `Pool<Sqlite>`
    = note: required for `Flash` to implement `FromRequestParts<Pool<Sqlite>>`
 note: required by a bound in `__axum_macros_check_quiz_grade_2_from_request_check`
   --> src/routes/learning_portal/quiz.rs:76:12
    |
 76 |     flash: Flash,
    |            ^^^^^ required by this bound in `__axum_macros_check_quiz_grade_2_from_request_check`

This prevents me from getting the true 'nice' errors debug_handler is supposed to generate. I can work around this by temporarily commenting out the parameter for Flash, but that means I need to make code-existence choices on the spot for debugging.

Is there a marker like #[no_debug] or something that can go directly on a parameter to stop this, or can I configure it to skip parameters like tracing::instrument can do?

I am using axum-flash v0.17.1 directly from a git commit due to the currently published version not compatible with axum's current version. It does work fine. Only issue is the debug_handler problem.

[dependencies]
axum-flash = { git = "https://github.com/davidpdrsn/axum-flash.git", rev = "0832703a0ca83b1ee35daaa8a199f68c2bcb4a90" }

I have also seen #1354 and the docs it links. This would work, I think, if I only had the Flash, but I also have an AppState struct extracted with the State extractor, and I'm unsure how to use both states with debug_handler. Setting #[axum::debug_handler(state=axum_flash::Config)] seems to fix the initial issue I had, but then it starts to complain about the State extractor.

 1  error[E0277]: the trait bound `Pool<Sqlite>: FromRef<axum_flash::Config>` is not satisfied
   --> src/routes/learning_portal/quiz.rs:74:18
    |
 74 |     State(pool): State<SqlitePool>,
    |                  ^^^^^ the trait `FromRef<axum_flash::Config>` is not implemented for `Pool<Sqlite>`
    |
    = help: the trait `FromRef<axum_flash::Config>` is not implemented for `Pool<Sqlite>`
            but trait `FromRef<AppState>` is implemented for it
    = help: for that trait implementation, expected `AppState`, found `axum_flash::Config`
    = note: required for `axum::extract::State<Pool<Sqlite>>` to implement `FromRequestParts<axum_flash::Config>`
    = help: see issue #48214

 2  error[E0277]: the trait bound `Pool<Sqlite>: FromRef<axum_flash::Config>` is not satisfied
   --> src/routes/learning_portal/quiz.rs:74:18
    |
 74 |     State(pool): State<SqlitePool>,
    |                  ^^^^^ the trait `FromRef<axum_flash::Config>` is not implemented for `Pool<Sqlite>`
    |
    = help: the trait `FromRef<axum_flash::Config>` is not implemented for `Pool<Sqlite>`
            but trait `FromRef<AppState>` is implemented for it
    = help: for that trait implementation, expected `AppState`, found `axum_flash::Config`
    = note: required for `axum::extract::State<Pool<Sqlite>>` to implement `FromRequestParts<axum_flash::Config>`
 note: required by a bound in `__axum_macros_check_quiz_grade_0_from_request_check`
   --> src/routes/learning_portal/quiz.rs:74:18
    |
 74 |     State(pool): State<SqlitePool>,
    |                  ^^^^^ required by this bound in `__axum_macros_check_quiz_grade_0_from_request_check

I am using the FromRef<SqlitePool> for AppState pattern.

Thanks.

axum version

0.8.5

[jplatte]

You can use #[debug_handler(state = AppState)], as explained further down in the macro's docs.

[damccull]

Heh. I guess I didn't understand how that worked. I thought I needed to include all the state types there, but it seems this state option is just telling the debug handler which is the application's state, specifically, and somehow this lets it give good feedback? Ok. Thanks!