idea: "import hook" automatically installed with editable builds

[davidhewitt]

I was thinking about "editable" / dev installs today and it struck me, should we support automatically installing the import hook for pip install -e editable installs?

It would be quite nice if maturin-backed packages installed in editable mode automatically used the import hook. I think it would be possible by putting the hook installation in a .pth file. Maybe once in maturin's .pth, and then the hook can work out what packages have been installed in editable mode / whether to recompile?

That could be an interesting trick to make local development of Rust packages more seamless for those not used to compiling...

[mbway]

not strictly related to the suggestion but I'm working on a new import hook here https://github.com/mbway/maturin-import-hook (which was originally here #1748).

Unlike the existing import hook, the new one supports detecting when rebuilds are necessary (including following path dependencies) and supports importlib.reload() (except on Windows right now).

It's not 100% finished but my idea for the workflow would be that for each virtualenv that you want to have the import hook available for you would run (once)

$ pip install maturin_import_hook
$ python -m maturin_import_hook site install

where I'm thinking the site subcommand could be passed install, info and uninstall for managing injecting the call to maturin_import_hook.install() into the site-packages/sitecustomize.py of the current environment. Or the user can add calls to maturin_import_hook.install() directly in each script that needs it if they prefer.

the installation of maturin_import_hook and optional injection into sitecustomize could also (optionally?) be done through maturin develop like you suggest.