"type 'Null' is not a subtype of type" on getter

[AdrienAudouard]

Hello,

I'm trying to generate a mock for a class witch contains a getter, the source code of the class is:

class AppContext {
...
  AppLocalizations get l10n => AppLocalizations.of(navigatorMaterialAppKey.currentContext!);
}

Then I generate a mock of the class with mockito and with the following code:

@GenerateNiceMocks([
  MockSpec<AppContext>(),
])

When I run the tests I have the following error: type 'Null' is not a subtype of type 'AppLocalizations', it look like in the generated code, the mock code of the getter is not generated.

Can you help me please ? 🙏

The generated code:

/// A class which mocks [AppContext].
///
/// See the documentation for Mockito's code generation for more information.
class MockAppContext extends _i1.Mock implements _i81.AppContext {
  @override
  _i28.GlobalKey<_i28.NavigatorState> get navigatorMainPageKey =>
      (super.noSuchMethod(
        Invocation.getter(#navigatorMainPageKey),
        returnValue: _FakeGlobalKey_34<_i28.NavigatorState>(
          this,
          Invocation.getter(#navigatorMainPageKey),
        ),
        returnValueForMissingStub: _FakeGlobalKey_34<_i28.NavigatorState>(
          this,
          Invocation.getter(#navigatorMainPageKey),
        ),
      ) as _i28.GlobalKey<_i28.NavigatorState>);
  @override
  _i28.GlobalKey<_i28.NavigatorState> get navigatorVaultKey =>
      (super.noSuchMethod(
        Invocation.getter(#navigatorVaultKey),
        returnValue: _FakeGlobalKey_34<_i28.NavigatorState>(
          this,
          Invocation.getter(#navigatorVaultKey),
        ),
        returnValueForMissingStub: _FakeGlobalKey_34<_i28.NavigatorState>(
          this,
          Invocation.getter(#navigatorVaultKey),
        ),
      ) as _i28.GlobalKey<_i28.NavigatorState>);
  @override
  _i28.GlobalKey<_i28.NavigatorState> get navigatorMaterialAppKey =>
      (super.noSuchMethod(
        Invocation.getter(#navigatorMaterialAppKey),
        returnValue: _FakeGlobalKey_34<_i28.NavigatorState>(
          this,
          Invocation.getter(#navigatorMaterialAppKey),
        ),
        returnValueForMissingStub: _FakeGlobalKey_34<_i28.NavigatorState>(
          this,
          Invocation.getter(#navigatorMaterialAppKey),
        ),
      ) as _i28.GlobalKey<_i28.NavigatorState>);
}

[srawlins]

Questions like this are best asked on a user forum like StackOverflow, with more eyes to look at the question.

[yanok]

Yep, it seems we don't override getters with non-nullable return type, but we have to. Thanks for reporting. I plan to re-work the codegen for Dart3 support significantly, I think this bug will be fixed too.

[yanok]

Yep, it seems we don't override getters with non-nullable return type, but we have to. Thanks for reporting. I plan to re-work the codegen for Dart3 support significantly, I think this bug will be fixed too.

The rewrite didn't fly, so I guess we just have to do the overrides.

[AdrienAudouard]

Okay, thanks for your reply, good luck 😄

[yanok]

Actually I can't reproduce it. And the line that does the getter override is there since 2020.

So, your generated code does indeed look wrong, but I don't understand how that could happen.

• Which version of Mockito do you use?
• What is the package:analyzer version?
• Which language version do you use for your project?
• Do you use mixed mode, with some sources being at one language version, while others at another one? Especially with regard to nullability feature?

[yanok]

@AdrienAudouard ping, I can't fix it if I can't reproduce it :)

[Ahmad-Hamwi]

@yanok Hi, I have the issue and I've reproduced it in this repo.
It's a very minimal project, please take a look. All required info is in the readme file.

[yanok]

This should be in the FAQ, I guess. You must declare variables holding mock objects to have Mock* types. In your code
here https://github.com/Ahmad-Hamwi/mockito-gen-issue/blob/5879e544b97b3c08a8176b4ffd6a914331de9a68/test/app_localizations_mockable.dart#L14

  late IAppLocalization mockAppLocalization;

MUST be

  late MockIAppLocalization mockAppLocalization;

[Ahmad-Hamwi]

If I understand OOP correctly, this shouldn't be the problem, should it? Since the runtime type will be a Mock* anyways.

But here's a screenshot after changing what you've suggested, and running the test again, the test still fails with the same error:

[yanok]

Oh, sorry, my bad. While what I said is correct and you still have to declare your mocks to have Mock types (since that's static type that matters while checking if method arguments have correct type), in your case the error indeed comes from something else. There gotta be a generated override for instance getter and it's missing in the generated code.

Thanks for the reproduction. I'll take a look a bit later.

[Ahmad-Hamwi]

Sure no problem.
Thank you for reopening the issue. Tyt.

[yanok]

The problem with your code is AppLocalizations having InvalidType at the time of Mockito codegen running. This is because Analyzer can't find package:flutter_gen/gen_l10n/app_localizations.dart under .dart_tool/flutter_gen. I actually wonder what makes it work when it runs "for real".

[Ahmad-Hamwi]

Thank you for you insights.

So basically generated code cannot be mocked. Is this an intended behavior for mockito or is it a feature that should be worked on?

Also, can you elaborate on what you mean about "for real"? Do you mean running the test in an emulated environment such as an integration test?

[yanok]

No, we can mock generated code, though there are also possible issues, since we have to be sure other generators run before mockito, and I think there is no generic way to ensure this. Actually this might be the cause here too, I thought the problem is the "magic" import, but maybe mockito generator just runs before flutter_gen?

By "magic" import I mean that this flutter_gen package is a bit special: it allows you to refer to the generated code via package:flutter_gen/... URLs, while it's clearly not a part of package:flutter_gen itself. So there is some magic setting that allows Dart to find these generated files.

By "for real" I mean when you run the test with flutter test or whatever vs when running the mockito codegen. Since for the codegen we spawn the Analyzer manually, so maybe we are missing some settings that make these "magic" imports work, as the problem seems to be Analyzer can't resolve these imports.