0.12.10 and next steps towards Mill 1.0.0

[lihaoyi]

0.12.10 was just released and contains the non-breaking changes that have been landing in main. Please try it out if you are able!

The major changes that we've wanted to get into 0.13.x have mostly landed:

• build.mill files compiled by Scala 3 #3369
• Remove Agg in favor of Seq #4525
• [WIP] Make Evaluator only available to Task.Command(exclusive = true) #3717
• Integrate os.Checker to sandbox filesystem IO #4635)
• Restrict sources and inputs to not accept upstream tasks #4524
• Replace import $file syntax with flat package namespacing #4462
• Clean up Discover macro and codegen #4461
• Renames, privatizations, and other API cleanups (too many to list)

Not everything has landed, and there will be continued work, but the bulk of breaking 1.0.0 changes are in.

Approximate Timeline of Next Steps:

• Early April: Re-bootstrap Mill's own codebase on top of the 1.0.0 branch.
• April: continue work on Mill, resolve any issues that get surfaced by the re-bootstrapping
• Early May: cut the first 1.0.0-RC1
• May: Re-bootstrap rest of com-lihaoyi projects onto Mill 1.0.0, encourage testing by broader community
• Late-May: Cut 1.0.0 final

[lihaoyi]

Probably the last major change I want to get into 0.13.0 is #2703. This would set Mill on a much better technical foundation with cleaner classpaths for the runner, user code, and plugins. It will require an overhaul of the BSP/GenIdea codebases, which will be a lot of work, but probably can get that done by the May target date for RC1

[lefou]

What I really like into 0.13, but which isn't that well discussed is a better concept for various test tasks. What I really envision is a way where all test runners share some state, so a testCached after a successful testForked doesn't need to run at all. I could imagine we could use a worker to keep/access that state.

[lihaoyi]

I'm planning on naming the 0.13.x series to 1.0.0. According to SemVer,

If your software is being used in production, it should probably already be 1.0.0. If you have a stable API on which users have come to depend, you should be 1.0.0. If you’re worrying a lot about backward compatibility, you should probably already be 1.0.0.

So I think naming it 1.0.0 is already overdue. This doesn't stop us from making breaking changes in future, it just means that the next breaking versions will be 2.0.0, 3.0.0, etc. which will better align with people's expectations for what the different version bumps mean

[rgwilton]

I think labelling it as 1.0.0 is a great idea, since it gives the industry more confidence in the stability of the tooling and the project overall.

[lihaoyi]

It's coming to end-April, and I'm looking at the following tentative dates

• 1 May until May 13:
  • The last major blocker before 1.0.0 is probably Mill sonatype central publishing doc #4928. With OSSRH being sunset in June 30th, we need to make sure the instructions for publishing via Sonatype Central are included as the primary workflow before then, backport it to 0.12.x, and migrate all of com-lihaoyi over to the new code path to make sure it works.
  • Apart from that, we're mostly looking at continued cleanup and polish for the various big changes that were made recently: classpath isolation, YAML metadata, BSP overhaul
• May 13: Publish 1.0.0-RC1
• May 13 - June 7:
  • Re-bootstrap all of com-lihaoyi on top of 1.0.0-RC1
  • Fix any issues that appear in the reboostrapping, or are reported by external users trying out the RC
  • Publish follow up RCs as necessary
  • Backport features to 0.12.x where possible to ease in the migration process
• June 7: Publish 1.0.0 final
• June 7 Until June 14:
  • Time for third-party plugins to re-publish for 1.0.0
• June 14:
  • Announce 1.0.0 Final for widespread use

[lihaoyi]

It's May 13 and all the major changes I'd like to land before RC1 have landed. I'd like to land #5110 to smooth the migration instructions to Sonatype Central before we cut 1.0.0-RC1, but may not have time to get to it today. If not, I'll likely get to it this coming weekend, which would mean 1.0.0-RC1 would get cut 17/18 May instead of 13 May