Unclear error handling

Is your feature request related to a problem? Please describe. I’m learning Fritz2, and I’m making a login form. When user enters bad credentials, and the API returns HTTP 401, I’d like to show the error (toast). I can’t find a way how.

Another related issue is in Tracker. When I start the remote request, and it fails, the button keeps spinning and I couldn’t find any method how to stop it.

Describe the solution you’d like

• Make special chapter in documentation about error handling.
• Demonstrate it in remotes example.
  • I have uBlock, which blocks the request to the domain you use in this example. I see the error in developer console, but nothing in the UI.

Abouty the tyracker problem, I’d suggest to change the track method like this:

// OLD (0.10.1)
return operation().also { state.value = null } 

// NEW
return try { operation() } finally { state.value = null }

Describe alternatives you’ve considered I couldn’t find any. Just provide some documentation and example.

Additional context My handler looks like this. If you could show me how to display the error toast, I’d be grateful.

val login = handle { model ->
    loading.track {
        if (validator.isValid(model, Unit)) {
            try {
                http("/apiIs2/authUser")
                    .acceptJson()
                    .contentType("application/json")
                    .body(
                        JSON.stringify(
                            json(
                                "username" to model.login, "password" to model.password
                            )
                        )
                    )
                    .post()
                    .getBody()
                router.navTo("main")
            } catch (t: Throwable) {
                console.log(t)
                toast { // NOT DISPLAYED :(
                    content {
                        alert {
                            title("Login error")
                            content(
                                if (t is FetchException && t.statusCode == 401.toShort()) {
                                    "Bad credentials"
                                } else {
                                    "$t"
                                }
                            )
                        }
                    }
                }
            }
        }
        model
    }
}

[chausknecht]

Ok, I have to correct myself: Of course it is quite easy to make track safe for unsafe operations.

I already provided PR #430 to improve this situation!

[EvaBS]

I display my errors like this:

// my serverErrorStore is of type <MyMessage?>, you could use ComponentValidationMessage or whatever else fits your usecase

// in RenderContext, render all server messages in the same place in app. 
// you could also make this store a list for multiple messages 
serverErrorStore.render { message ->
    if (message != null) {
        showToast {
            content {
                alert { content( //... message content) }
            }
        }
    }
}

// in REST-Handler in Store when error occurs:
serverErrorStore.update(thisErrorMessageWhichOccurredJustNow)

// clear store when you're done with the error, I do that when I enter a handler or new page content is rendered
serverErrorStore.update(null)