Multiple Apps

[JPHutchins]

I decided to convert a project to multiple apps in order to share some GUI base classes. It works great!

When it comes to the pyproject.toml, I found that I had to copy out all of the entries like [tool.briefcase.app.firstapp.linux.system.suse] and repeat them with [tool.briefcase.app.secondapp.linux.system.suse] etc. Is there anyway to avoid this repetition and declare that all of the apps have the same briefcase dependencies?

[freakboy3742]

If the dependency is common to all app on all platforms, you can include the requirement in the project-level requires setting (i.e. in [tool.briefcase])

If the dependency is linux specific, but shouldn't be used on macOS/Windows, there's no "across all apps, on linux" section where you can put a declaration. That might be worth exploring as a feature; the question would be the exact resolution order (i.e., do platform level declarations come before or after app level declarations?)

However, there is another option: you can use PEP508 install qualifiers in the app-level section. For example:

[tool.briefcase]
...
requires = [
    "pillow==9.3.0; sys_platform == 'linux'",
    "pillow==9.2.0; sys_platform == 'darwin'",
]

This would install Pillow 9.3.0 on Linux, but Pillow 9.2.0 on macOS. You can use any of the qualifiers here (so, for example, you can gate installation on the Python version to install a backwards compatibility shim like importlib_metadata).

The only complication with this is that sys.platform == 'linux' on Android as well (at least, it does until Python 3.13; as of Python 3.13, Android reports as sys.platform == "android"). But if you're not planning to target Android, that's not a concern, it's entirely safe to use.