unusedCompileDependenciesFilter usage

[anilkumarmyla]

I seemingly used unusedCompileDependenciesFilter as specified in README.md, but got errors during sbt run

project/build.properties

sbt.version=1.2.8

project/plugins.sbt

addSbtPlugin("com.timushev.sbt" % "sbt-updates" % "0.4.0")
addSbtPlugin("com.github.cb372" % "sbt-explicit-dependencies" % "0.2.9")

build.sbt

unusedCompileDependenciesFilter -= moduleFilter("org.scalaz", "scalaz")

sbt update

error: No implicit for Remove.Value[explicitdeps.ModuleFilter, sbt.librarymanagement.ModuleFilter] found,
  so sbt.librarymanagement.ModuleFilter cannot be removed from explicitdeps.ModuleFilter
unusedCompileDependenciesFilter -= moduleFilter("org.scalaz", "scalaz")
                                ^
[error] Type error in expression
Project loading failed: (r)etry, (q)uit, (l)ast, or (i)gnore? q

[anilkumarmyla]

Apparently this is caused by including the sbt-updates plugin
If I have addSbtPlugin("com.timushev.sbt" % "sbt-updates" % "0.4.0") in project/plugins.sbt , I get the above error message

[cb372]

I'm glad you found the cause just as I was about to start looking at this 😄

It's quite surprising though. Both plugins define their own type alias for sbt.librarymanagement.ModuleFilter (explicitdeps.ModuleFilter and com.timushev.sbt.updates.Compat.ModuleFilter respectively) but I wouldn't expect that to be a problem.

I'll do some digging and see if I can at least find a workaround.

[anilkumarmyla]

thanks @cb372, this error baffles me since explicitdeps.ModuleFilter is a type alias for sbt.librarymanagement.ModuleFilter . I've tried some workarounds but none seemed to work

[cb372]

@anilkumarmyla I've found a workaround:

unusedCompileDependenciesFilter := moduleFilter() - moduleFilter("org.scalaz", "scalaz")

[anilkumarmyla]

@cb372 It works! Have you gotten to the root cause of the behavior?

[anilkumarmyla]

Just remembered that the documentation should also mention how to filter multiple modules rather than a single one so as to make the syntax clearer 😄

[cb372]

I've found the cause, and I'm an idiot. It's an ambiguous implicit.

sbt doesn't provide an instance of Remove.Value for ModuleFilter (maybe it should), so sbt-updates provides one here.

When I found that code in sbt-updates previously, I liked the idea and shamelessly stole it. So there's an identical instance in sbt-explicit-dependencies here, which causes an ambiguous implicit when you use both plugins. I completely forgot that I'd done that!

[anilkumarmyla]

Interesting, I'd expect the scala compiler to throw an error/warning about the ambiguous implicit.