Enforce ScalaFmt/PalantirJavaFormat/KtLint on example doc/test suites (500USD Bounty)

[lihaoyi]

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From the maintainer Li Haoyi: I'm putting a 500USD bounty on this issue, payable by bank transfer on a merged PR implementing this.

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Currently managing the formatting for this is manual, and sometimes inconsistencies slip through. We should really just automate enforcement and compliance.

We should as much as possible re-use the infrastructure Mill has already built around these autoformatters, to dogfood it. This would mean doing the autoformatting as part of Mill's own Mill build, using the various ScalaFmtModule/PalantirJavaFormatModule/KtLintModules as necessary

[LevisNgigi]

Hello interesting but I think this might not be beginner friendly for someone new to the project.Will be on the lookout for other issues.

[Sailsman63]

In this context, what does "Automate enforcement and compliance" look like?

• Just surface the errors in the build script CI, block PRs on fixing them
• Automatically apply and commit fixes on merge
• Other?

[lihaoyi]

Just surface the errors in the build script CI, block PRs on fixing them

Just this, with some manual command that can be run to fix them locally. Same as the current workflow.

[myyk]

I'm going to see if I can figure this one out tomorrow

[lihaoyi]

@myyk some pointers if you're going to look into this:

1. This should be purely a change in the build.mill/package.mill files, shouldn't need any application code changes

2. The default mill.scalalib.scalafmt.ScalafmtModule defaults to looking for __.sources, so the easiest thing to do would be to hook into that by defining a sources in ExampleCrossModule that points to testRepoRoot so it can get picked up by ScalafmtModule/formatAll and checkFormatAll

3. To make this work for Java sources as well, we would need to run PalantirFormatModule in addition to ScalafmtModule in CI here

4. The example tests rely on comments being formatted in specific ways to be parsed and used as test commands. We may need to tweak add docstrings.style = keep to our .scalafmt.conf to preserve them as is

[myyk]

Thanks! I was trying to piece together 2, that helps a lot. That all makes sense.