Unnecessary implicit conversion while using experimental catseffect AsyncValue

[roman0x58]

Hello there, I'm trying to eliminate the need for the Future with the functionality described here: #987. However, I'm encountering a lot of ambiguity errors in places where F[X] is used. The implicit conversion in the AsyncValue object is attempting to convert the types to LeafAction. Please see the errors above for more details. Do you have any advice on how to address this ambiguity? Thanks!

[error] 133 |        parentPrice <- fs2.Stream.eval(collection(ctx).findById(parentId).compile.toList.map(_.headOption))
[error]     |                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]     |Found:    F[List[O2]]
[error]     |Required: ?{ map: ? }
[error]     |
[error]     |where:    F  is a type in class PriceDictionary with bounds <: [_] =>> Any
[error]     |          O2 is a type variable with constraint >: model.TreeElement[model.PriceItem]
[error]     |
[error]     |Note that implicit extension methods cannot be applied because they are ambiguous;
[error]     |both method asyncAction in object AsyncValue and method toFunctorOps in trait ToFunctorOps provide an extension method `map` on (fs2.Stream.CompileOps[[x] =>> F[x], [x] =>> F[x], O2]#toList : => F[List[O2]])

[error] 86 |    (for {
[error] 87 |      user <- c.ctx.om.mongo.users
[error] 88 |        .findOne(or(equal("email", email), equal("login", email)))
[error] 89 |        .compile
[error] 90 |        .toList
[error] 91 |        .map(_.headOption)
[error] 92 |    } yield user match {
[error] 93 |      case Some(u) => checkAuthContext(u, c.arg(Context))(process(_))
[error] 94 |      case _ => failForm[UserPassport]("email", messages("om.auth.violation.notfound"))
[error] 95 |    }).flatten
[error]    |    ^
[error]    |value flatten is not a member of sangria.schema.LeafAction[Nothing, F[auth.UserPassport]], but could be made available as an extension method.

[yanns]

Thanks for the report.
Indeed, the scala compiler seems to transform the F[_] into a LeafAction too early.
Maybe I'll need to push the implicit conversion into a trait to give it less priority.
I can try that later.

I'm not sure if we would have the same issue when using Future.

For the moment, as a workaround, we can add type hints.
Or better, you could extract your logic into another function returning the F[_] and only call this function from sangria. That way, you would make sure that your business logic is not coupled with sangria.

[roman0x58]

Thanks for the tips, @yanns! Decoupling sangria and the business layers indeed seems like the best option. However, implementing this would require a significant amount of work due to our solid codebase. For now, I think I'll stick with the cats dispatcher.

[yanns]

I think I have a solution for that.
But before, I'm trying to reproduce your issue, but I could not. Here is my try: #1156
Maybe you could help here?

[roman0x58]

I think I have a solution for that. But before, I'm trying to reproduce your issue, but I could not. Here is my try: #1156 Maybe you could help here?

I replied to your pull request. I think the second case with flatten leads to the first