Update scala-library to 2.13.9 #370

typelevel-steward · 2022-09-22T09:01:21Z

Updates org.scala-lang:scala-library from 2.13.8 to 2.13.9.
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labels: library-update, early-semver-patch, semver-spec-patch, commit-count:n:2

Executed command: sbt githubWorkflowGenerate

danicheg · 2022-09-25T07:30:12Z

shared/src/main/scala/mouse/MouseFunctions.scala

@@ -32,6 +30,10 @@ trait MouseFunctions {
   * @param a
   *   - the value to be evaluated and ignored.
   */
-  def ignore(@nowarn a: Any): Unit = ()


According to the new behavior in Scala 2.13.9, this @nowarn was marked as unused.

home/runner/work/mouse/mouse/shared/src/main/scala/mouse/MouseFunctions.scala:35:15: @nowarn annotation does not suppress any warnings
[error] def ignore(@nowarn a: Any): Unit = ()

And it's done intentionally. So we had to handle this issue with some workaround.

@benhutchison your thoughts on this would be appreciated.

Annoying and ironic that suppressing warnings generates a warning!

But if there's no warning, can we remove the annotation?

This new behavior is only for 2.13.9. So, if we just remove the annotation, then for 2.12 and 3 that will cause warnings about unused function argument.

benhutchison · 2022-09-25T08:44:38Z

This is such an incompatible change! Maybe we hold off on 2.13.9 and see if they reverse it due to popular outcry? Alternative would be a version specific source file but that's a lot of bother for such a small issue..

…

On Sun, 25 Sept 2022, 5:50 pm Daniel Esik, ***@***.***> wrote: ***@***.**** commented on this pull request. ------------------------------ In shared/src/main/scala/mouse/MouseFunctions.scala <#370 (comment)>: > @@ -32,6 +30,10 @@ trait MouseFunctions { * @param a * - the value to be evaluated and ignored. */ - def ***@***.*** a: Any): Unit = () This new behavior is only for 2.13.9. So, if we just remove the annotation, then for 2.12 and 3 that will cause warnings about unused function argument. — Reply to this email directly, view it on GitHub <#370 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAAXJZDMQVKRHPAS6QIWG73V7775TANCNFSM6AAAAAAQS2RNUU> . You are receiving this because you were mentioned.Message ID: ***@***.***>

danicheg · 2022-09-25T08:59:34Z

Alternative would be a version specific source file but that's a lot of
bother for such a small issue..

I agree with this. This approach would require us to do a lot of copy-pasting. Our codebase will lose some maintainability.

Maybe we hold off on 2.13.9 and see if
they reverse it due to popular outcry?

It took 9 months for the new release to come. It will be a long run. 🤷🏻‍♂️

benhutchison · 2022-09-25T10:19:36Z

My vote is to sit out 2.13.9 for now, this sort of incompatible change in late stage maintenance release is crazy

…

On Sun, 25 Sept 2022, 6:59 pm Daniel Esik, ***@***.***> wrote: Alternative would be a version specific source file but that's a lot of bother for such a small issue.. I agree with this. This approach would require us to do a lot of copy-pasting. Our codebase will lose some maintainability. Maybe we hold off on 2.13.9 and see if they reverse it due to popular outcry? It took 9 months for the new release to come. It will be a long run. 🤷🏻‍♂️ — Reply to this email directly, view it on GitHub <#370 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAAXJZGOAXJO7AJYJEB5YMLWAAIADANCNFSM6AAAAAAQS2RNUU> . You are receiving this because you were mentioned.Message ID: ***@***.***>

satorg · 2022-09-25T16:56:13Z

I agree with this. This approach would require us to do a lot of copy-pasting. Our codebase will lose some maintainability.

Alternatively, it is possible to implement a version-specific @nowarn. But if you think Scala-compiler folks may decide to revert the change, then it is not worth it, apparently.

satorg · 2022-09-25T17:21:36Z

... or perhaps another alternative could be leveraging -Wconf for 2.13.9 with the origin (UPD. or site?) parameter to suppress unnecessary "unused" warnings:

Syntax: -Wconf:<filters>:<action>,<filters>:<action>,...
multiple <filters> are combined with &, i.e., <filter>&...&<filter>

...

<filter>
  ...
  - Site where the warning is triggered: site=my\.package\..*
    The regex must match the full name (`package.Class.method`) of the warning position.

  - Origin of deprecation: origin=external\.package\..*
    The regex must match the full name (`package.Class.method`) of the deprecated entity.

But it would require to point out all the undesired warning origins in compiler options, of course 🤷

danicheg · 2022-09-26T12:44:18Z

@satorg

or perhaps another alternative could be leveraging -Wconf for 2.13.9 with the origin (UPD. or site?) parameter to suppress unnecessary "unused" warnings:

Wouldn't that lead to warnings on the user side on using the ignore function?

satorg · 2022-09-27T05:41:36Z

@danicheg I have been poking around the -Wconf and other compiler settings. And there are good and bad news to bring up:

Bad news: I could not make -Wconf working with the site filter option.
The only filters that are working for mouse.MouseFunctions#ignore are something like site=.* or site=^.*$ or site=^.?$ or something like that. Which basically means that "site" is just empty (!) there. Perhaps @som-snytt could help to clarify on how the site filter is supposed to work in such cases.
Good news: turned out that although Scala v2.13.9 does not tolerate @nowarn anymore but it does tolerate @unused.
Bad news: (well, not the news, actually) Scala v2.12 does not have @unused.
Good news: the latter can be simulated via @nowarn in a "compiler-compat" way.
Bad news: by default it produces another warning.
Good news: that warning can be suppressed gracefully too.

Bottomline: it seems that it can be made working afterall. See #372 as an example on how it could be addressed.

satorg · 2022-09-27T05:53:01Z

...I would also dare to argue that regardless of the changes in v2.13.9 the @unused annotation is generally preferable over @nowarn for suppressing various unused stuff.

som-snytt · 2022-09-27T07:01:22Z

Under -Wunused:params -Xlint or equivalent:

// 2.12.17, 2.13.8 warn C&D
// 2.13.9 warns D only
// the E is silent

import annotation._

class C {
  def f(x: String): Unit = ()
}

class D {
  def f(x: String): Unit = (): Unit
}

class E {
  def f(@nowarn x: String): Unit = (): Unit
}

Don't miss the proposal for -Xlint:confused scala/bug#11631 (comment)

This proposal from the original ticket was not adopted:

Not warning on meh is an easy win.

som-snytt · 2022-09-27T07:09:10Z

I'm reminded that this does not warn because the signature is foreordained:

trait T {
  def f(x: String): Unit
}

class X extends T {
  def f(x: String): Unit = (): Unit
}

som-snytt · 2022-09-27T08:11:16Z

Also from the original proposal for @unused, this does not warn:

def dep(@deprecated("not used", since="now") x: String): Unit = (): Unit

So the idea was for unused to extend deprecated. The proposal for custom unused extending nowarn rang this bell.

satorg · 2022-09-27T09:11:06Z

Yeah, I saw that @deprecated-based approach is used in the scala-collection-compat library:
https://github.com/scala/scala-collection-compat/blob/d6723b241ab943f8f0e7da21292c7994ce4d9f80/compat/src/main/scala-2.11_2.12/scala/annotation/unused.scala#L15

Unfortunately it is not perfect either. Consider this simplified example from cats (syntax for Either, actually):

import scala.reflect.ClassTag

trait NotNull[A]

class CatchOnlyPartiallyApplied[T](val dummy: Boolean) extends AnyVal {
  //def apply[A](f: => A)(implicit CT: ClassTag[T], @deprecated("unused", "now") NT: NotNull[T]): Either[T, A] =
  //def apply[A](f: => A)(implicit CT: ClassTag[T], @annotation.nowarn("cat=unused") NT: NotNull[T]): Either[T, A] =
  def apply[A](f: => A)(implicit CT: ClassTag[T], NT: NotNull[T]): Either[T, A] =
    try {
      Right(f)
    } catch {
      case t if CT.runtimeClass.isInstance(t) =>
        Left(t.asInstanceOf[T])
    }
}

The line without any annotation produces an "unused" warning (apparently)
v2.12.17:

[warn] ./fromCatsEitherSyntax.scala:8:51: parameter value NT in method apply is never used
[warn]   def apply[A](f: => A)(implicit CT: ClassTag[T], NT: NotNull[T]): Either[T, A] =
[warn]                                                   ^

v2.13.9:

[warn] ./fromCatsEitherSyntax.scala:8:51: parameter value NT in method apply is never used
[warn]   def apply[A](f: => A)(implicit CT: ClassTag[T], NT: NotNull[T]): Either[T, A] =
[warn]                                                   ^^^^^^^^^^^^^^

However(!), if we try to utilize @deprecated to suppress the unused warning, then we'll end up with a way weirder one:
v2.12.17:

[warn] ./fromCatsEitherSyntax.scala:9:5: value NT is deprecated (since now): unused
[warn]     try {
[warn]     ^

v2.13.9:

[warn] ./fromCatsEitherSyntax.scala:9:5: value NT is deprecated (since now): unused
[warn]     try {
[warn]     ^

Whereas @nowarn("cat=unused") (or a custom @unused inherited from that) works just fine for this case 🤷

danicheg · 2022-09-27T09:30:26Z

It blows my mind, but type ascription really helps to tackle the issue with @nowarn. @som-snytt thanks for this workaround.
@benhutchison could you re-review this PR? Now it seems pretty fine to get PR merged.

benhutchison

Nice and simple!

typelevel-steward bot and others added 3 commits September 22, 2022 09:00

Update scala-library to 2.13.9

b077ee1

Regenerate GitHub Actions workflow

573138d

Executed command: sbt githubWorkflowGenerate

Fix issue with nowarn for MouseFunctions#ignore

acbe977

danicheg reviewed Sep 25, 2022

View reviewed changes

satorg mentioned this pull request Sep 27, 2022

Better update to Scala v2.13.9 #372

Closed

satorg mentioned this pull request Sep 27, 2022

Disable fatal warnings on 2.12 if cross-building? typelevel/sbt-typelevel#378

Closed

Use type ascription to workaround the @nowarn issue

6823c15

benhutchison approved these changes Sep 27, 2022

View reviewed changes

danicheg merged commit 3f8bb6a into main Sep 27, 2022

danicheg deleted the update/scala-library-2.13.9 branch September 27, 2022 13:28

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Update scala-library to 2.13.9 #370

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Update scala-library to 2.13.9 #370

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