Fix -Wconf:src Windows path conversion

[mbland]

Updates the -Wconf:src filter to avoid using java.nio.file.Path.toURI in order to fix Windows source path conversions.

Path.toURI prepends the current working directory to Windows-like paths unconditionally, and converts backslashes in such paths to %5C escape sequences This can cause -Wconf:src filters that work on non-Windows platforms to fail on Windows.

For example, before this change, the Path.toURI conversion in the SourcePattern case from MessageFilter.matches() produced:

original: Optional[C:\foo\bar\myfile.scala]
resolved: /Users/mbland/src/scala/scala3/C:%5Cfoo%5Cbar%5Cmyfile.scala

After this change, it produces the following, which still prepends the current working directory, but properly converts path separators to /:

original: Optional[C:\foo\bar\myfile.scala]
resolved: /Users/mbland/src/scala/scala3/C:/foo/bar/myfile.scala

This change is based on scala/scala#11192, and also adapts some test cases from that pull request to validate symlink and normalized path handling. This change also extracts the diagnosticWarning helper method to reduce duplication between new and existing test cases.

Fixes #24771. Review by @lrytz.

[lrytz]

After this change, it produces the following, which still prepends the current working directory, but properly converts path separators to /:

original: Optional[C:\foo\bar\myfile.scala]
resolved: /Users/mbland/src/scala/scala3/C:/foo/bar/myfile.scala

After blowing the dust off my Windows VM, I can confirm this is platform dependent.

On Windows:

scala> java.io.File("C:\\foo\\..\\bar\\f.txt").toPath.toAbsolutePath.normalize
val res0: java.nio.file.Path = C:\bar\f.txt

scala> java.io.File("C:\\foo\\..\\bar\\f.txt").toPath.toAbsolutePath.toUri.normalize.getRawPath
val res1: String = /C:/bar/f.txt

On macOS:

scala> java.io.File("C:\\foo\\..\\bar\\f.txt").toPath.toAbsolutePath.normalize
val res0: java.nio.file.Path = /Users/luc/code/scala/scala13/sandbox/C:\foo\..\bar\f.txt

scala> java.io.File("C:\\foo\\..\\bar\\f.txt").toPath.toAbsolutePath.toUri.normalize.getRawPath
val res1: String = /Users/luc/code/scala/scala13/sandbox/C:%5Cfoo%5C..%5Cbar%5Cf.txt

So arguably the current implementation using toUri is also OK..?

[mbland]

So arguably the current implementation using toUri is also OK..?

Hmm, arguably, yes. So if you want, I could:

• Close this pull request outright (and maybe open a new one for Scala 2 that uses toURI and removes the Windows path assertions, to ensure parity between the implementations?)
• Pare the changes down to only add the new tests (minus the Windows path test), which may be good to have
• Keep the pull request as it is, to make the Scala 3 implementation closer to the implementation from Don't resolve symlinks in -Wconf:src scala#11192

One other thing I noticed was that, unlike the Scala 2 implementation, the src filter doesn't automatically prepend / to patterns to ensure they match an entire path component. For example, this currently fails:

  @Test def `Wconf src filter only matches entire directory path components`: Unit =
    val path = Path("foobar/File.scala")
    val result = wconfSrcFilterTest(
      argsStr = "-Wconf:src=bar/.*\\.scala:s",
      warning = diagnosticWarning(util.SourceFile(new PlainFile(path), "UTF-8"))
    )
    assertEquals(result, Right(reporting.Action.Warning))

Note that the current tests reverse the expected, actual ordering of the assertEquals parameters, so the assertion failure message reads backwards:

[error] Test dotty.tools.dotc.config.ScalaSettingsTests.Wconf src filter only matches entire directory path components failed:
  java.lang.AssertionError: expected:<Right(Silent)> but was:<Right(Warning)>, took 0.001 sec
[error]     at dotty.tools.dotc.config.ScalaSettingsTests.Wconf src filter only matches entire directory path components(ScalaSettingsTests.scala:308)

So the fourth option would be:

• Repurpose this pull request so that src path prefixes only match entire directory path components.