How to initialise an empty venv with no app?

[robinbowes]

How would this feature be useful?

I have a library package, and an app that uses the library package. Both are local-only, ie. I install them with pip install /path/to/library and pip install /path/to/app

I want to install app with pipx, but if I run pipx install /path/to/app it fails because library is not available.

I can't see how I can install library into the app venv before installing app.

Describe the solution you'd like

One possible workflow might be:

• create an empty venv with a specified name
• inject any dependencies into the venv
• inject the app into the existing venv, using --include-apps to create symlink(s) for the app into $HOME/.local/bin

In my use-case:

• pipx init foo
• pipx inject foo /path/to/library
• pipx inject --include-apps foo /path/to/app

So, what I need is the some command to create an empty venv into which I can inject dependencies and apps (the pipx init foo in the example above)

Describe alternatives you've considered
I have hacked a solution like this:

• Install an arbitrary app to create a venv (I used cowsay)
• Inject library into the cowsay venv
• Inject app into the cowsay venv with --include-apps

app is now available

Suggestions for better ideas would be much appreciated.

[uranusjr]

This sounds like a packaging issue in you app. Python packages shouldn’t require another package to be present during installation, only when the package code is actually run. While pre-installation injection may be a good feature to have, this would not be a use case for it.

[robinbowes]

Python packages shouldn’t require another package to be present during installation, only when the package code is actually run

I'm not sure I agree with that. In my experience, when I install a package (local, or remote) it also makes sure any packages required by that package are installed, ie. those listed in the install_requires section of setup.cfg. The install will fail if those dependencies are not available.

[robinbowes]

Looking at the source, it seems that a relatively easy way to achieve this would be to add an option to the inject command which creates the named package if it does not exist, installs the provided dependencies, and doesn't exit with an error if no app is installed. Something like:

pipx inject --create app dep1 dep2
pipx inject --include-apps app

I also tried specifying the deps with --pip-args , but that didn't work:

pipx install --pip-args="/path/to/library" /path/to/app
Cannot determine package name from spec '/path/to/app'.
Check package spec for errors.

[dukecat0]

Maybe the --preinstall feature added in #900 can help in this case?

[gaborbernat]

Maybe the --preinstall feature added in #900 can help in this case?