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.