Hello hello! Got a doubt regarding apollo v4 excep...

# apollo-kotlin

[Marco Pierucci]

Hello hello! Got a doubt regarding apollo v4 exception handling and authentications 🧵

[Marco Pierucci]

suspend fun <D : Operation.Data> ApolloCall<D>.executeAsResult(): Result<D> = with(execute()) {
    val requestId = findRequestIdHeader()
    when {
        hasErrors() -> {
            val message = errors?.joinToString { it.message }
            Result.failure(KrakenFieldClientException(message.orEmpty()))
        }

        exception != null -> Result.failure(
            wrapResponseException(
                exception = exception!!,
                requestId = requestId,
                operation = operation,
            ),
        )

        data != null -> Result.success(data!!)

        else -> {
            Result.failure(KrakenFieldNotCompliantServerException("No data or errors in response"))
        }
    }
}

We wrote the following extensions tu execute queries/mutaiton and return a result of the operation.
We used to use try cat but afaik with apollo 4 apollo shoudl not throw and rather use exception field

[Marco Pierucci]

so far so good

[Marco Pierucci]

the problem is that we also have an authenticator added to the client, which at some point we attempt at re authenticate the user. For that call we only catch one exception we are interested in and let the other bubble up

[Marco Pierucci]

Our assumption was that because the authenticator is added to the client internal machinery of the client, any exception thrown there would be handled by it and be part of the exception field mentioned above.

[Marco Pierucci]

But we've been doing some tests and it seems that thats not the case and the exception is re thrown ( thus breaking our original as result function

[Marco Pierucci]

Is this correct?

[mbonnin]

we also have an authenticator added to the client

That's OkHttp, right?

[mbonnin]

Any exception thrown by OkHttp should be caught here and exposed in ApolloResponse.exception

[mbonnin]

So I'm tempted to say your expectations are correct.

[mbonnin]

But if you're seeing an exception that is not handled then obviously something is off somewhere

[Marco Pierucci]

Its an ApolloInterceptor actually

[mbonnin]

Gotcha yea, that one shouldn't throw

[mbonnin]

You can return an exception response to the upstream interceptors

[mbonnin]

But throwing will tear the interceptor chain down

[Marco Pierucci]

> Gotcha yea, that one shouldn't throw
As in us devs should not be throwing within the interceptor, or as in if something its thrown its handled eventually with the exception field of the response

[mbonnin]

If ApolloInterceptor.intercept() throws, nothing is going to catch the exception to turn in into an exception field

[mbonnin]

If OkHttp throws, your interceptor receives an exception response

[Marco Pierucci]

cristal clear! thanks for the speedy response

[mbonnin]

Sure thing!

[Marco Pierucci]

You can return an exception response to the upstream interceptors

This bit is not fully clear

[Marco Pierucci]

How could I return such a response from the intercept method?

[mbonnin]

You can use ApolloResponse.Builder.exception()

[Marco Pierucci]

I see! Perfect thanks

[mbonnin]

For an exemple, this is done here

[mbonnin]

(No need to do the isLast() dance, this is something I'm trying to remove actually)

[mbonnin]

try {
              // do your stuff here
            } catch (e: Exception) {
              return flowOf(
                  ApolloResponse.Builder(request.operation, request.requestUuid)
                  .exception(exception)
                  .build()
              )
            }

[Marco Pierucci]

Noted, much appreciated!

[Marco Pierucci]

So the exception property takes only an apollo exception,
we do

DefaultApolloException(
                                message = e.message,
                                cause = e,
                            )

Altho it feels a bit nasty. I guess we can only catch ApolloExceptions

[mbonnin]

Agree, this is awkward but very hard to change. DefaultApolloException is the way to go

[mbonnin]

Idea was to give a base class to make exception more discoverable but that didn't age well.

[Marco Pierucci]

Makes sense, thats ok we'll go with this approach and soem docs. Cheers again! Enjoy your afternoon