Improve REPL echo and exception highlighting with pprint and fansi

[lihaoyi]

Before:

After:

Rather than just rendering everything as plaintext and coloring it later, we:

• Preserve the colors that PPrint applies to the pretty-printed text.
  • This means that for objects which are not handled via PPrint and go via their toString, we do not spuriously highlight parts of them depending on the specific hex hashcodes etc.
  • This also means we can distinguish between the integer 123 and new Object{ override def toString = "123" }, as the former will be colored as a literal while the latter will be white

• We manually color exception stack traces using Fansi. This generally just looks a lot better, again without random parts of it being highlighted or not depending or whether specific regexes match class names or file names.

  • I kept it mostly red-and-white, to avoid the "rainbow" of noisy colors that was there before and making it obviously it's a failure. The
  • I kept the exception .getMessage in white, in case the exceptions have their own colored messages so we don't over-write their colors

• For everything else, we continue using the prior highlighting logic

Some of the logic was refactored to pass around fansi.Strs rather than java.lang.Strings to make it easier to keep track of colors, but otherwise I tried to minimize the churn and keep the overall code structure unchanged

[Gedochao]

LGTM

[Gedochao]

@hamzaremmal assigning you to make sure this doesn't clash with #24243 (I'm pretty sure it would)

[hamzaremmal]

Not until I get #24243 in.

[lihaoyi]

@hamzaremmal now that #24243 has landed, shall I rebase this on top of latest main?

[hamzaremmal]

Yes please. All the REPL PRs should be rebased.

[lihaoyi]

@hamzaremmal I'm getting the following error trying to run bin/scala clean on the latest main, which blocks manual testing of this feature.

Please bear in mind that non-ideal user experience should be expected.
If you encounter any bugs or have feedback to share, make sure to reach out to the maintenance team at https://github.com/VirtusLab/scala-cli
Error: Could not find or load main class dotty.tools.repl.Main
Caused by: java.lang.ClassNotFoundException: dotty.tools.repl.Main

[hamzaremmal]

@hamzaremmal I'm getting the following error trying to run bin/scala clean on the latest main, which blocks manual testing of this feature.

Please bear in mind that non-ideal user experience should be expected.
If you encounter any bugs or have feedback to share, make sure to reach out to the maintenance team at https://github.com/VirtusLab/scala-cli
Error: Could not find or load main class dotty.tools.repl.Main
Caused by: java.lang.ClassNotFoundException: dotty.tools.repl.Main

That is expected at the moment since scala-cli doesn't have any knowledge of the new artifact scala3-repl. @Gedochao is working on releasing the next version of scala-cli that support this next week. Speaking of, I'm actually writing an email to you and Eugene about mill and sbt respectively since neither of them now work too.

[Gedochao]

@Gedochao is working on releasing the next version of scala-cli that support this next week.

• Add support for the new Scala 3.8 REPL VirtusLab/scala-cli#3936