add back the implicit method as explicit to maintain BC

[kailuowang]

No description provided.

[rossabaker]

Looks good, but I'm going to be super pedantic and go through the rest just so we don't need a 1.3.2 for this. Stay tuned.

[rossabaker]

I tested all the other MiMa exceptions, and those are sound.

We can also remove this exception, since it shouldn't have been:

exclude[DirectMissingMethodProblem]("cats.data.OptionTInstances.catsDataMonadForOptionT")

[rossabaker]

Yep, perfect.

[kailuowang]

@rossabaker I just removed the exception

[johnynek]

It’s dangerous to add to the Mima exceptions I guess.

[rossabaker]

We could have automated test on exceptions. Compile this in an unpublished cats module that builds against the desired cats-core in Provided scope:

object MimaExceptions {
    def isBinaryCompatible = {
      cats.data.OptionT.catsDataTraverseForOptionT[List]
      cats.data.Kleisli.catsDataCommutativeArrowForKleisliId
      cats.data.OptionT.catsDataMonoidKForOptionT[List]
      cats.data.OptionT.catsDataMonoidForOptionT[List, Int]
      cats.data.Kleisli.catsDataMonadForKleisliId[Int]
      cats.data.Kleisli.catsDataCommutativeArrowForKleisli[Option]
      cats.data.Kleisli.catsDataCommutativeFlatMapForKleisli[Option, Int]
      cats.data.IRWST.catsDataStrongForIRWST[List, Int, Int, Int]
      cats.data.OptionT.catsDataMonadErrorMonadForOptionT[List]
      true
  }
}

And then the test, which depends on the unpublished module:

class MimaExceptionsTest {
  test("is binary compatible") { 
    MimaExceptions.isBinaryCompatible
  }
}

It's more or less what I did in a side repo to verify the others. And it would have caught this one.

[rossabaker]

Note: I don't want the above test idea to slow the bugfix. If others like the idea, we can always add it after 1.3.1.

[codecov-io]

Codecov Report

Merging #2471 into master will decrease coverage by 0.01%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #2471      +/-   ##
==========================================
- Coverage   95.39%   95.38%   -0.02%     
==========================================
  Files         357      357              
  Lines        6516     6517       +1     
  Branches      288      282       -6     
==========================================
  Hits         6216     6216              
- Misses        300      301       +1

Impacted Files	Coverage Δ
core/src/main/scala/cats/data/OptionT.scala	95.91% <0%> (-0.99%)	⬇️

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