did 2.2.0 break bincompat on 2.11?

[SethTisue]

old tickets that explain the problem are: #288, #292, #249

PR with the breakage: #341, and then I wrongly added a MiMa exclusion in #356

most recent discussion: #356 (but let's continue here)

on #356 @NthPortal wrote:

What is the correct thing to do now?

• move the method to the package objects, draft a new release ASAP, and make a note that the release was bad and shouldn't be used?
• leave it as is?
• have the method in both places?

[SethTisue]

move the method to the package objects, draft a new release ASAP, and make a note that the release was bad and shouldn't be used

I think this is what we should do. Besides the handful of people active on the tickets, probably only Scala Steward users even noticed the release, and if we do a prompt followup release, the steward will send followup PRs.

But I will bring it up at our team meeting in a few hours and see what others think.

[SethTisue]

I just found #162, in which @szeiger and @dwijnand both made the exact same argument I made:

the trait is package-private (which MiMa doesn't see) and should not be extended by users

as a result, releases since 2.1.1 have not been binary compatible with 2.0.0, if we are right that this form of change is not safe

[SethTisue]

@julienf are you certain that the change is not safe, even though the trait is package-private? I cannot locate any ticket or discussion in which any case is laid out that this is actually a problem for a trait which the end user cannot extend

[lrytz]

I also think the new MiMa rule

exclude[ReversedMissingMethodProblem]("scala.collection.compat.PackageShared.*"), // it's package-private

is correct. The backwards bin compat issue is that subclasses of the trait need to be recompiled to gain a mixin forwarder method which implements the new abstract method in the interface. All subclasses are known, part of the library itself, so we're fine.

[julienrf]

Sorry, I overlooked at the problem, it seems that we are safe!

[NthPortal]

does that mean we can deduplicate the other methods back into PackageShared?

[SethTisue]

@julienrf better a surplus of caution than a shortage!

does that mean we can deduplicate the other methods back into PackageShared?

let's try it: #368