@GenerateMocks does not generate correct stub for generic Future return Types

[MaxAuer]

Hey,

I tried to generate a Mock for the following Function:

Future<T> update<T extends Base>(T data);

Several classes are extending Base.

flutter pub run build_runner build does output the following stub:

@override
  _i3.Future<T> update<T extends _i4.Base>(T? data) =>
      (super.noSuchMethod(Invocation.method(#update, [data]),
          returnValue: Future.value(null)) as _i3.Future<T>);

I then use the following when in my test to stub the function

when(api.update<Base>(any)).thenThrow(Exception());

Which gives the following error type 'Future<Null>' is not a subtype of type 'Future<Note>' in type cast. This does make sense as Future.value(null) can not be parsed to Future<T> which is not nullable.

The correct behavior should be a value that can be parsed to Future<T>.

[hoc081098]

Same issue :(

[hoc081098]

Trick: edit returnValue: Future.value(xxx) where xxx is value of testing type

[MaxAuer]

Maybe worth checking this issue out: Mocktail-Type-Safety. @srawlins

He could solve this without any code generation. Sure it`s a breaking change but maybe its worth checking out for Mockito.

[srawlins]

Mocktail uses strings for mocking, in which case you lose all type safety, typo protection, static analysis, etc. We will not be moving in that direction.

[MaxAuer]

Sorry to contradict.

The issue I linked was opened by me because I saw the same issues with Mocktail. It was lacking type safety but works without code generation. Felix found a solution based on lambdas to have type safety without code generation and working with null safety.

He also proposed merging mockito into mocktail: #347

[kuhnroyal]

I also have a lot of Future.value(null) return values generated that don't compile with strict analyzer settings.
This should be generated as Future<T>.value(null) to work with all kinds of analysis_options.yaml configurations.

[srawlins]

@MaxAuer sorry I got my projects mixed up.

[srawlins]

@kuhnroyal can you elaborate? analysis_options.yaml does not affect compilation.

[kuhnroyal]

@srawlins You are correct. What I meant to say is, that with strong-mode and language settings on, the files are red in the IDE as these are not analyzer warnings but errors.

analyzer:
  language:
    strict-inference: true
    strict-raw-types: true
  strong-mode:
    implicit-dynamic: false
    implicit-casts: false

I know that I can exclude the generated files from analysis but it would be nice if the generated code conforms to these setting as it will then also conform to less strict settings. This would make it easier to add to projects.

[srawlins]

Thanks @kuhnroyal . That sounds like a separate issue from this issue. I can take a look if you file a separate issue, and include the new static errors you are seeing.

[srawlins]

A fix for this issue is available now with Mockito 5.0.9, "fallback generators". Please see the new section in the NULL_SAFETY_README:

https://github.com/dart-lang/mockito/blob/master/NULL_SAFETY_README.md#fallback-generators

[tomwyr]

@srawlins Correct me if I'm wrong here, but since we don't care about actual results of Future objects and fallback generators serve only to make generated code null-safe, couldn't Mockito just return Completer<T>().future?

In a similar way methods that return generic streams are currently mocked. The difference here is that instead of a stream that never emits we just want a future that never completes.