Coroutine-variant is throwing while blocking equivalent is not

I’m implementing some kind of custom caching. Because of this 304 is an interesting response for me. When getting the Triple from .response() I correctly get a Result, which is a failure. When using .awaitResponse() the continuation is throwing instead. Of course I could try-catch the FuelError, but I believe changing Fuels behaviour so that the coroutine-case matches the default case makes more sense.

My code looks like this:

class CachedHttpLineSource(private val prefs: Prefs, private val uri: String, private val userName: String, private val password: String, private val cacheDir: File) : LineSource() {
    @Serializable
    data class CachedFile(val uri: String, val etag: String?, val savedPath: String)

    private fun getDownloadRequest(etag: String? = null): Request {
        val req = Fuel.download(uri).authenticate(userName, password)
        if (etag == null) return req
        return req.header("If-None-Match" to etag)
    }

    private suspend fun download(etag: String? = null): CachedFile {
        val file = File(cacheDir, uri.sha1())
        if (file.exists()) file.delete()
        val triple = getDownloadRequest(etag).destination { _, _ -> file }.awaitResponse() // does throw here
        val response = triple.second
        val result =  triple.third
        when (result) {
            is Result.Failure -> { throw(result.getException()) } // should throw here
            is Result.Success -> { return CachedFile(uri, response.headers["ETag"]?.firstOrNull(), file.absolutePath) }
        }
    }
}

Looking into Coroutines.kt reveals the problem. Using fold for all cases instead of just returning the Triple seems wrong. As far as I understand it could work to just remove the folding and resume with the Triple in any case as the .third.get() should throw the exception in the relevant cases too.

// line 23
    response(deserializable) { request: Request, response: Response, result: Result<T, FuelError> ->
        result.fold({
            continuation.resume(Triple(request, response, result))
        }, {
            continuation.resumeWithException(it.exception)
        })
    }
    
// line 32
suspend fun Request.awaitResponse(): Triple<Request, Response, Result<ByteArray, FuelError>> =
        await(byteArrayDeserializer())
        
// line 43
suspend fun Request.awaitResponseResult(): ByteArray = awaitResponse().third.get()

[lucasvalenteds]

@georg-jung The pull request #373 has been merged and should solve this issue.

[lucasvalenteds]

@D-A-R Now I see what you mean there. Thank you for the clarification. So it seems that it’s related to the other issue.