8000 Scalafix rewrite(s) for 2.12->2.13 non-collection library changes · Issue #11430 · scala/bug · GitHub
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dwijnand opened this issue Nov 27, 2018 · 7 comments
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Scalafix rewrite(s) for 2.12->2.13 non-collection library changes #11430

dwijnand opened this issue Nov 27, 2018 · 7 comments
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@dwijnand
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dwijnand commented Nov 27, 2018 •
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(Related scala/scala-dev#327 which seems to be about language changes in 2.13)

There are a number of changes in the standard library, to the point I think 2.13 should ship with a Scalafix rewrite for them.

In particular, I'm thinking of scala/scala#5830 (which is a re-submission of scala/scala#5677) which deprecated a number of things and suggests these replacements:

(2019-05-09 edit: No, it didn't. The original PR did, the re-submission just removed the already-deprecated code.)

To compensate for the associated deprecations in your own code:

  • compat.Platform.EOL --> add import java.lang.System.{lineSeparator => EOL}
  • compat.Platform.currentTime --> add import java.lang.System.{currentTimeMillis => currentTime}
  • compat.Platform.arraycopy --> add import java.lang.System.arraycopy
  • sys.error --> throw new RuntimeException (or subclass)
  • sys.exit --> System.exit
  • sys.props --> System.getProperties().asScala (with import scala.collection.JavaConverters._)
  • sys.env --> System.getenv().asScala
  • sys.runtime --> Runtime.getRuntime
  • sys.addShutdownHook --> Runtime.getRuntime.addShutdownHook(new Thread(() => ...))
  • Console.BOLD --> AnsiColor.BOLD (with import scala.io.AnsiColor)
  • Console.readLine --> Console.in.readLine()
  • concurrent.Lock --> java.util.concurrent.locks.ReentrantLock (lock/unlock)

I argue that deprecations in the standard library affect the entire ecosystem, so the release should come with a (or multiple) rewrites. Not because the migration is hard, but because it's so vastly impacting. I would expect it to be much easier than the collection rewrites.

I optimistically target 2.13.0-RC1 🙂
@Jasper-M
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Jasper-M commented Nov 28, 2018 •
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I seem to have missed/ignored those PRs, but I would like to point out that System.exit is not a direct replacement for sys.exit. The java one has return type Unit, while the Scala one has (the more accurate) return type Nothing.

i.e.

scala> val parsedArg: Int =  util.Try(??? : Int).fold(_ => {println("Usage: ..."); System.exit(1)}, identity)
                                                                                              ^
       error: type mismatch;
        found   : Unit
        required: Int

It's a bit unfortunate that some of these more Scala friendly alternatives would disappear, and then every project needs to factor out the extra boilerplate themselves.

@smarter
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smarter commented Nov 30, 2018

@Jasper-M Looks like this isn't actually deprecated currently: https://github.com/scala/scala/blob/2.13.x/src/library/scala/sys/package.scala I also agree some of those are worth keeping around.

@adriaanm adriaanm transferred this issue from scala/scala-dev Mar 13, 2019
@adriaanm adriaanm added this to the 2.13.0-RC1 milestone Mar 13, 2019
@SethTisue SethTisue modified the milestones: 2.13.0-RC1, 2.13.0 Apr 3, 2019
@dwijnand dwijnand self-assigned this May 1, 2019
@dwijnand
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dwijnand commented May 1, 2019

I've implemented these in https://github.com/dwijnand/scala-rewrites.

@olafurpg any chance I could get you (and/or anyone else with Scalafix expertise) to review it?

If the Scala maintainers like it I was thinking I could transfer the repo to the scala org so it can be an official part of the 2.13.0 release.

@olafurpg
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olafurpg commented May 2, 2019

@dwijnand I'm happy to review, where is the best place to leave comments?

For example, matching against Term.Select below
https://github.com/dwijnand/scala-rewrites/blob/ab9e425e4499fc13d3b3451ce6393c05e3541f08/rewrites/src/main/scala/fix/Scala_2_13.scala#L141
will make the rewrite do nothing when colors are referenced as plain identifiers BLACK from a wildcard import Console._.

@dwijnand
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dwijnand commented May 2, 2019

@olafurpg 1-n issues and/or 1-n PRs to the repo, if that works for you.

Good point about Term.Name. I handle that for EOL, but not everywhere. I'll do that.

@dwijnand
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dwijnand commented May 9, 2019

Updated the ticket: The PR that landed didn't add all those deprecations. The original PR did, but the re-submission just removed the already-deprecated code.

I'm continuing to progress in the scala-rewrites repo.

@dwijnand
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Closing in favour of progress being made and tracked in https://github.com/scala/scala-rewrites.

@SethTisue SethTisue removed this from the 2.13.0 milestone May 15, 2019
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