Fix: mix format crashes in umbrella projects

[matthewsinclair]

Running mix format at umbrella root crashes with a MatchError in Mix.ProjectStack.

The Problem

The fix for #228 (commits 9eddbeb and 0d1048a) added compilation before formatting
to ensure modules are available. This breaks umbrella projects because calling
Mix.Task.run("compile") from within a formatter plugin triggers recursive
compilation, violating Mix.ProjectStack's expectations.

Changes

• Added safe_compile/0 that checks Mix.Project.umbrella?() before compiling
• Skips compilation at umbrella root, runs normally elsewhere
• Added graceful error handling when modules can't be loaded
• Improved error messages in the mix task for umbrella users
• Added test coverage

Fixes #231

[zachdaniel]

I've added some more logic here, mind pulling and updating? Thank you for the fix 🙇

[matthewsinclair]

Thanks, Zach. LGTM for the merge.

[zachdaniel]

Not sure if I messed it up again but there are still conflicts 😢

[matthewsinclair]

Not sure what the issue is? When I run the tests on my side on the PR branch in my fork, I get clean tests:

$ git status
On branch fix/umbrella-format-crash
Your branch is up to date with 'origin/fix/umbrella-format-crash'.

nothing to commit, working tree clean

$ mix test
Generated spark app
Running ExUnit with seed: 815428, max_cases: 32

..................................................................................................
Finished in 3.6 seconds (0.4s async, 3.1s sync)
5 doctests, 93 tests, 0 failures

What conflicts are you seeing? Or are you referring to the merge conflict below on lib/spark/formatter.ex?

Let me see if I can fix it on my side ... ok, should be good go now.

[zachdaniel]

Please fix credo then I'll merge 🙇

[matthewsinclair]

Done.

[zachdaniel]

Actually...I was just about to merge this when I had a thought that this would be a pretty jarring experience for folks using this, because not being able to run mix format from the root. I assume you have an umbrella app here that hits this. Seems like what we should do is put this plugin in the .formatter.exs of those child projects? Would that potentially solve this?

[matthewsinclair]

not run mix format from root

But that isn't how it works, or at least that's not how my fork works as far as I know. I am using my fork of this, and it works fine from the root of an umbrella project. It just checks to stop the recursion. But now you've got me worried that my fork and the mainline have diverged.

[zachdaniel]

Oh, nvm. You're good.