Workaround for trait with associated types and lifetimes

[dsomerfield-vendia]

I have a fairly complex case where I have to cast some associated types that have lifetimes. I'm not terribly surprised that automock can't figure it out, but I also haven't been able to figure out if there is a work-around. This is the an example of the situation that I can't mock:

#[async_trait]
trait Repo {
    type QueryEngine: QueryEngine;

    async fn run_query(&self, query: &<Self::QueryEngine as QueryEngine>::Query<'_>) -> Result<(), ()>;
}

I have tried to do a manual mock, but haven't been able to create it in a way that the mock! macro will accept. Here is the mock I tried to create:

    mock! {
        Repo {}

        #[async_trait]
        impl Repo for Repo {
            type QueryEngine = MockQueryEngine;

            async fn run_query(&self, query: &<Self::QueryEngine as QueryEngine>::Query<'_>) -> Result<(), ()>;

        }

    }

When I manually mock, it doesn't seem to like code generated by mock!, specifically, the Self reference (ambiguous associated type) and the inferred lifetime (missing lifetime specifier). Is there anyway, I can provide some hints, or possibly make some assumption that will allow the generated code to be acceptable. Full example with full error message is here.

Incidentally, the example is async, but it I have removed all async code and that doesn't seem to be affecting anything at this point.

[dsomerfield-vendia]

It figures. After fighting with this for hours, I might have just figured it out. This manual mock seems to work:

    mock! {
        Repo {}

        impl Repo for Repo {
            type QueryEngine = MockQueryEngine;
            fn run_query<'a>(&self, query: &<<MockRepo as Repo>::QueryEngine as QueryEngine>::Query<'a>) -> Result<(), ()>;
        }

    }

I need to validate whether that is semantically the same as the inferred lifetime, but this gives me a path forward. I

[asomers]

Issue #541 describes the same anonymous lifetime problem, and shows a workaround. As for Self, you could try replacing it with MockRepo.

[dsomerfield-vendia]

You are so right on both counts. Thank you! I was very close, but this nudged me to the solution.

BTW, if you are looking for contributors to this project, let me know. I'm becoming a very dedicated user and would love to give back.