Running `pip install .` in a Briefcase project causes error "application must have a formal name"

[NMertsch]

What is the problem or limitation you are having?

After running pip install . in a briefcase project using toga, briefcase dev will crash with "Toga application must have a formal name". That's quite confusing and not helpful.

Why does this happen?

• pyproject.toml is present, so pip recognizes the directory as a valid Python package.
• pyproject.toml does not contain PEP 621 project metadata (section project), so pip uses default values: Version: 0.0.0, Name: <your-project-dirname>.
  • pip does NOT pick up the briefcase project metadata from the section tool.briefcase.
• pip creates src/<your-package>.egg-info/ containing this minimal set of project metadata.
• briefcase dev creates src/<your-package>.dist-info/ with the correct metadata
• toga.app.App.__init__() uses importlib.metadata.metadata(sys.modules["__main__"].__package__).get("Formal-Name") to get the Format-Name metadata, which is not present in the egg-info, so it raises a RuntimeError.

Maybe the tutorial should be clearer about when to use pip vs when not to use pip.

Describe the solution you'd like

I don't know enough about Python packaging, metadata discovery, egg-info vs dist-info and probably other relevant topics. I hope that someone else can pick up from here to find a solution.

Describe alternatives you've considered

Potential approaches (some way be wrong/bad/impossible):

• briefcase dev aborts with a useful error message if egg-info exists.
• briefcase dev ignores egg-info, so toga uses the correct metadata from dist-info.
• pip install . fails instead of being "accidentally successful".
• pip install . finds the correct metadata.
• briefcase dev creates/overwrites egg-info instead of dist-info.
• Update the tutorial to provide better guidance on when to use and not to use pip vs briefcase vs modifying pyproject.toml.

Additional context

No response

[mhsmith]

What are you trying to achieve with pip install .? Making the project's modules interactively importable for debugging?

Whatever your intentions, pip install -e . is almost certainly a better choice, as it'll avoid making a copy of your code, so any changes will be picked up without needing to run pip again.

This may also be helped by using a current version of pip, which will always install via a wheel in both editable and non-editable mode. The directory it creates will therefore always be called dist-info, not egg-info.

[mhsmith]

You're going outside of the normal Briefcase workflow here, but if the problem is the absence of a project section in your pyproject.toml file, then there's nothing stopping you from adding that section yourself. Briefcase already supports that section as an alternative to its own. See #1235 for further development in this area.

[NMertsch]

I don't say it's a good idea to run "pip install .", but I can imagine it to be a pretty mean noob trap. And from the activity in toga#1048 I assume I'm not the first one.

My main point isn't "please support this", but "please make it less hard to fix your setup if it happens".

My intention was to add my dependencies to pyproject.toml and run "pip install -e ." to install them, which is my normal workflow in non-beeware projects. If I had thought more about it, I would have known it doesn't work (section tool.beeware, not project).
And after I did this, toga just crashed with a seemingly unrelated error message. It took me a while to find out what's wrong.