Enqueued MockServer response null

[rb090]

Question

Hi 👋,

I am trying to write some unit tests for my Apollo code and I want to use this nice MockServer. Nonetheless, when enqueue responses to it and execute my "mock query", I end up in ApolloResponse with data and errors null.

I am using com.apollographql.apollo3:apollo-testing-support v4.0.0-beta.4 and com.apollographql.apollo3:apollo-mockserver v4.0.0-beta.4

And I don't know why. Can you please have a quick look and tell me what I am doing wrong?

// Create apollo mock server
val mockServer = MockServer()

// Enqueue HTTP responses
mockServer.enqueue(
    mockResponse = MockResponse.Builder().statusCode(statusCode = 200)
        .headers(headers = headers)
        .body(body = """
              {
                "data": {
                    "getUser": {
                        "birthdate": "1990-11-08T00:00:00",
                        "city": null,
                        "country": null,
                        "deactivationTimestamp": null,
                        "email": "roxana@company.de",
                        "firstName": "Roxana",
                        "gender": "FEMALE",
                        "houseNr": null,
                        "id": "xxxx",
                        "lastName": "Test",
                        "phone": null,
                        "postalCode": null,
                        "salutation": "MRS",
                        "street": null,
                        "title": null,
                        "lastOnline": "2024-01-25T18:18:52"
                    }
                }
              }
        """)
        .build()
)

val apolloClient = ApolloClient.Builder().serverUrl(mockServer.url()).build()

val receivedUser = apolloClient.query(GetUserQuery()).execute()

mockServer.close()

// This shows me both attributes as null
println("receivedUser.data: ${receivedUser.data}")
println("receivedUser.errors: ${receivedUser.errors}")

[martinbonnin]

Hi 👋

Can you share your GetUserQuery? If it has any non-null fields that are not named random, it'll fail parsing and you should have an exception in receivedUser.exception.

[rb090]

Hi @martinbonnin,

thanks a lot for your answer on this. I do not get an exception. I corrected the body in my posted message and replaced with the actual body of my GetUserQuery. I used for this GitHub issue here initially a "test string".

My GetUserQuery looks like this:

query GetUser {
    getUser {
        ...MyUser
    }
}

fragment MyUser on BackendUser {
    id
    salutation
    title
    firstName
    lastName
    gender
    birthdate
    street
    houseNr
    postalCode
    city
    country
    phone
    email
    lastOnline
    deactivationTimestamp
}

And regarding parsing, I also tried to parse json with:

val jsonReader = BufferedSourceJsonReader(source = Buffer().write(mockResponseGetUser.encodeUtf8()))
val user = MyUserImpl_ResponseAdapter.MyUser.fromJson(jsonReader, CustomScalarAdapters.Empty)

And mockResponseGetUser had the content of the body.

In that case I got exception

Expected a name but was BEGIN_OBJECT at path 
com.apollographql.apollo3.exception.JsonDataException: Expected a name but was BEGIN_OBJECT at path 
	at app//com.apollographql.apollo3.api.json.BufferedSourceJsonReader.nextName(BufferedSourceJsonReader.kt:407)
	at app//com.apollographql.apollo3.api.json.BufferedSourceJsonReader.selectName(BufferedSourceJsonReader.kt:707)
	at app//com.sth.backend.api.apollo.codegen.fragment.MyUserImpl_ResponseAdapter$MyUser.fromJson(MyUserImpl_ResponseAdapter.kt:76)
	at app//com.sth.mobile.requests.ApolloExtensionsTest$Success unwrap apollo response$1.invokeSuspend(ApolloExtensionsTest.kt:72)
	at app//com.sth.mobile.requests.ApolloExtensionsTest$Success unwrap apollo response$1.invoke(ApolloExtensionsTest.kt)
	at app//com.sth.requests.ApolloExtensionsTest$Success unwrap apollo response$1.invoke(ApolloExtensionsTest.kt)
.....
1 test completed, 1 failed
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':shared:testDebugUnitTest'.
> There were failing tests. See the report at: file:///.../shared/build/reports/tests/testDebugUnitTest/index.html
* Try:
> Run with --scan to get full insights.
BUILD FAILED in 788ms

I use the apollo library within a kotlin multiplatform project.

[martinbonnin]

val user = MyUserImpl_ResponseAdapter.MyUser.fromJson(jsonReader, CustomScalarAdapters.Empty)

This is internal APIs, you're not really supposed to call them directly. If you want, you'll need to call .obj():

-val user = MyUserImpl_ResponseAdapter.MyUser.fromJson(jsonReader, CustomScalarAdapters.Empty)
+val user = MyUserImpl_ResponseAdapter.MyUser.obj().fromJson(jsonReader, CustomScalarAdapters.Empty)

The public API to do the same thing is GetUserQuery().parseResponse(source). It also allows passing in variables and other information required to parse @include and @defer correctly

Back to your original problem, can you try adding __typename to your JSON?

{
                "data": {
                    "getUser": {
                        "__typename": "BackendUser",
                        "birthdate": "1990-11-08T00:00:00",
                        "city": null,
                        "country": null,
                        "deactivationTimestamp": null,
                        "email": "roxana@company.de",
                        "firstName": "Roxana",
                        "gender": "FEMALE",
                        "houseNr": null,
                        "id": "xxxx",
                        "lastName": "Test",
                        "phone": null,
                        "postalCode": null,
                        "salutation": "MRS",
                        "street": null,
                        "title": null,
                        "lastOnline": "2024-01-25T18:18:52"
                    }
                }
              }

The Apollo Compiler queries __typename automatically for polymorphism and cache reasons. If it doesn't find it, it will fail the parsing as well (and you should get an exception in response.exception)

[martinbonnin]

PS: Note that the exception is not thrown, it's part of response.exception. This is a change in v4. See this issue for more details.

[rb090]

@martinbonnin thank you so so much ❤️. Ya it was mit good old friend __typename 😂🙈. Now, when setting __typename within the json like you proposed, the MockResponse gets enqueued perfectly. Thank you for your patience and your explanations. That helps really a lot.

Regarding the obj().fromJson:

This is internal APIs, you're not really supposed to call them directly. If you want, you'll need to call .obj():

-val user = MyUserImpl_ResponseAdapter.MyUser.fromJson(jsonReader, CustomScalarAdapters.Empty)
+val user = MyUserImpl_ResponseAdapter.MyUser.obj().fromJson(jsonReader, CustomScalarAdapters.Empty)

Ah okay, thank you for clarification that this is internal and should not be used from outside. I now used GetUserQuery().parseResponse(source) and that worked like a charm.

val user = MyUserImpl_ResponseAdapter.MyUser.obj().fromJson(jsonReader, CustomScalarAdapters.Empty) call with .obj(). still ends up in error:

Field 'id' is missing or null at path [null]
com.apollographql.apollo3.exception.DefaultApolloException: Field 'id' is missing or null at path [null]
	at app//com.apollographql.apollo3.api.Assertions__AssertionsKt.missingField(Assertions.kt:38)
	at app//com.apollographql.apollo3.api.Assertions.missingField(Unknown Source)
	at app//com.backend.api.apollo.codegen.fragmentMyUserImpl_ResponseAdapter$MyUser.fromJson(MyUserImpl_ResponseAdapter.kt:110)
	at app//com.backend.api.apollo.codegen.fragment.MyUserImpl_ResponseAdapter$MyUser.fromJson(MyUserImpl_ResponseAdapter.kt:35)
	at app//com.apollographql.apollo3.api.ObjectAdapter.fromJson(Adapters.kt:359)
	at app//com.myapp.mobile.requests.ApolloExtensionsTest$Success unwrap apollo response$1.invokeSuspend(ApolloExtensionsTest.kt:74)
	at app//com.myapp.mobile.requests.ApolloExtensionsTest$Success unwrap apollo response$1.invoke(ApolloExtensionsTest.kt)
	at app//com.myapp.mobile.requests.ApolloExtensionsTest$Success unwrap apollo response$1.invoke(ApolloExtensionsTest.kt)
	at app//kotlinx.coroutines.test.TestBuildersKt__TestBuildersKt$runTest$2$1$1.invokeSuspend(TestBuilders.kt:319)
	at app//kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
	at app//kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:108)
	at app//kotlinx.coroutines.test.TestDispatcher.processEvent$kotlinx_coroutines_test(TestDispatcher.kt:28)
	at app//kotlinx.coroutines.test.TestCoroutineScheduler.tryRunNextTaskUnless$kotlinx_coroutines_test(TestCoroutineScheduler.kt:103)
...

I am not sure why, this is just FYI maybe there is an issue somewhere?

PS: Note that the exception is not thrown, it's part of response.exception. This is a change in v4. See #4711 for more details.

Aaaahh okay 👍, oh this is cool tbh 😍, so thank you for the hint here. From what I see now, there is exception in case of network failure fe.

Nonetheless, there is also ApolloException thrown on ApolloCall<D : Operation.Data>.execute(). But this exception is called when:

if the call returns zero or multiple valid GraphQL responses.

Do I understand it correctly that this is thrown in case ApolloResponse.data and ApolloResponse.errors and ApolloResponse.exception are null? Or when there is an ApolloResponse.exception AND ApolloResponse.data?

[martinbonnin]

Field 'id' is missing or null at path [null]

My bad, MyUserImpl_ResponseAdapter.MyUser is expecting a User (without data), not a response so if you're using that you need to pass a JSON that looks like { "id": ..., "firstName": ...}, etc...

But using parseResponse() is much better and will avoid those kind of issues.

execute(): ApolloException is thrown if the call returns zero or multiple valid GraphQL responses.

execute() throws if the call returns zero or multiple responses. When this happens this is typically a programming mistake. For an example, you used .execute() on a subscription (that returns multiple responses) or on a @defer query. In those cases, you need to call .toFlow().

For server/network errors, etc.. it's all in response.exception.

• You can have data == null && errors == null && exception == null if a server is non-compliant and returns {}
• It's impossible to have exception != null && data != null though. If you have data, it means a response was successfully returned and therefore exception is always null.

I typically recommend to handle errors like this:

if (response.data != null) {
  // Handle (potentially partial) data
} else {
  // Something wrong happened
  if (response.exception != null) {
    // Handle non-GraphQL errors (network, cache miss, etc...)
  } else {
    // Handle GraphQL errors in response.errors
  }
}

If you don't want to deal with partial data, you can opt-in the new error-aware parsing. You can read https://www.apollographql.com/docs/kotlin/v4/advanced/nullability#error-aware-parsing for more details.

Hope this helps!

[rb090]

@martinbonnin thank you so much for the explanation and the informations. Now everything makes sense for me.

I really like the new Error aware parsing within apollo v4 😍 - very nice addition.

But do I understand it correctly, that when I specify throwing errors in case that parsing fails with extend schema @catch(to: THROW) it is for all queries and mutations?

And in case I want some queries and mutations to behave different from that "standard" and to display the data returned from the server, even if it is partial I would need to configure @catch for the single attributes where I am okay with the failing right?

[martinbonnin]

And in case I want some queries and mutations to behave different from that "standard" and to display the data returned from the server, even if it is partial I would need to configure @catch for the single attributes where I am okay with the failing right?

That is correct. With extend schema @catch(to: THROW), the error handling becomes opt-in. You'll have to opt-in on individual fields with @catch(to: NULL) or @catch(to: RESULT) if needed.

[rb090]

Ah okay. That make totally sense, now I got the whole idea on that and how it works. And I will start using it.

Thanks a lot for the explanations 🙌 ❤️. I guess now my questions are totally answers and I really learned again a lot about the Kotlin apollo client which is a lot more nicer since the last time I used it 🙂.

I wish you a wonderful weekend and close this issue.

[martinbonnin]

Many thanks for the kind words 💙😃. Let us know how the error-aware parsing works for you. This is brand new functionality and your feedback is super important!