virtualfish: VirtualFish is not accessible after simple pip install

@whwkong: I recently added that Fish version check because folks were filing issues that were caused by using outdated Fish versions. As you can see in the relevant code, the version comparison should not produce the result you encountered. Here’s what happens when I run that code in a Python REPL:

~ ➤ python
Python 3.7.7 (default, Mar 10 2020, 15:43:27)
>>> pip install packaging
>>> import subprocess
>>> from packaging import version
>>> cmd = ["fish", "-c", "echo $version"]
>>> current_fish_version = subprocess.check_output(cmd).decode("utf-8").strip()
>>> print(version.parse(current_fish_version))
3.1.2
>>> minimum_fish_version = "3.1"
>>> print(version.parse(current_fish_version) < version.parse(minimum_fish_version))
False
>>> print(version.parse(current_fish_version) > version.parse(minimum_fish_version))
True

So I am baffled as to why that version comparison test failed in your case. Nonetheless, I suppose I can remove the exit() directive, effectively changing the Fish version check into merely a warning instead of preventing further VirtualFish use.

In the interim, in you should be able to comment out the check_fish_version() call on line 35 in /home/william/.local/lib/python3.7/site-packages/virtualfish/loader/cli.py and then run the following command to install the VirtualFish loader:

python /home/william/.local/lib/python3.7/site-packages/virtualfish/loader/cli.py install environment projects

I would really like to understand why the version check failed in your case, so if you find any information that would have led to that result, by all means please let me know.

For what it’s worth, I cannot replicate the behavior you mentioned:

~ ➤ trash ~/.config/fish/conf.d/virtualfish-loader.fish
~ ➤ exec fish  # Now `vf` command should no longer be recognized
~ ➤ vf
fish: Unknown command: vf
fish:
 vf
 ^
~ ➤ python -m venv ~/Virtualenvs/tempenv
~ ➤ source ~/Virtualenvs/tempenv/bin/activate.fish
(tempenv) ~ ➤ pip install virtualfish
(tempenv) ~ ➤ vf --version
VirtualFish is not installed. Run 'vf install' to install it, then run 'exec fish' to restart your shell and load it.
(tempenv) ~ ➤ vf install
VirtualFish is now installed! Run 'exec fish' to reload Fish, and you'll be able to use it!

In your case, Pip-installing VirtualFish does not result in having the vf command available on $PATH — I don’t know why. As you said, it could be something particular to your system. What is the path to the Python interpreter you used to Pip-install VirtualFish? What is displayed when you run the following command?

grep VIRTUALFISH_PYTHON_EXEC ~/.config/fish/conf.d/virtualfish-loader.fish

If someone successfully installs a Python package via Pip, but then that package’s entry point (in this case, vf) is not subsequently available to the user for some reason, then there isn’t really anything we can do to tell the user that something didn’t work correctly. We have no way to determine that. While in theory it is possible to use a Setuptools post-installation step to check for that condition, we switched from Setuptools to Poetry, the latter of which intentionally does not support arbitrary Python code execution during package installation (for security reasons).

In short, it would helpful to determine why installing the virtualfish package did not result in vf being available on your $PATH, because that is what should have happened.