add generic type to FetchCatsBackend stub method

[MirkoManojlovic]

Before submitting pull request:

• Check if the project compiles by running sbt compile
• Verify docs compilation by running sbt compileDocs
• Check if tests pass by running sbt test
• Format code by running sbt scalafmt

This PR adds a generic type to stub method in FetchCatsBackend companion object.
Reasoning for this change is, when you have SttpBackend defined as a dependency like this

 val catsBackend: SttpBackend[IO, capabilities.WebSockets] = FetchCatsBackend[IO]()

it is not possible to mock it using this code

val stubedBackend: SttpBackendStub[IO, Any] = FetchCatsBackend.stub[IO]

adding a type resolves this issue 😃

val stubedBackend: SttpBackendStub[IO, WebSockets] = FetchCatsBackend.stub[IO, WebSockets]

[adamw]

Thanks for the PR - following suit for other stub backends, I think it would be sufficient to simply type this using the WebSockets capability. Then you can upcast to Any because of variance. See e.g.:

sttp/effects/fs2/src/main/scalajvm/sttp/client3/httpclient/fs2/HttpClientFs2Backend.scala

Line 173 in d0fb7e9

def stub[F[_]: Async]: SttpBackendStub[F, Fs2Streams[F] with WebSockets] = SttpBackendStub(implicitly)

[MirkoManojlovic]

No no, thank you for the awesome lib, I'm just trying to give back a little 😄

For the reply, I'm not sure I get it. The docs for the second type parameter in SttpBackend say

P – Capabilities supported by this backend, in addition to sttp.capabilities.Effect. This might be Any (no special capabilities), sttp.capabilities.Streams (the ability to send and receive streaming bodies) or sttp.capabilities.WebSockets (the ability to handle websocket requests).

So should the change be, this? (then we only support Websockets? Not sure if FetchCatsBackend can support anything else?)

  def stub[F[_]: Async, WebSockets]: SttpBackendStub[F, WebSockets] = SttpBackendStub(new CatsMonadAsyncError)

or there should ne now change at all 😄

[adamw]

Yes, it should be changed as you described. In general this should be the maximal set of capabilities - you can always upcast a backend to narrow the supported capabilities list. In case of cats, it's only WebSockets, no streaming is supported.

[MirkoManojlovic]

Oh okay understood, thank you.

Code changed 😄

[adamw]

Thanks! :)