fish shell _pyenv_virtualenv_hook slow

[ephes]

Hi *,

thanks for this awesome project at first :).

I noticed that my fish shell got really slow when just pressing enter compared to bash and I figured out that the line "status --is-interactive; and source (pyenv virtualenv-init -|psub)" in my fish config caused this to happen. It looks like this line creates a function that listens to the fish_prompt event:

function _pyenv_virtualenv_hook --on-event fish_prompt
	set -l ret $status
  if [ -n "$VIRTUAL_ENV" ]
    pyenv activate --quiet; or pyenv deactivate --quiet; or true
  else
    pyenv activate --quiet; or true
  end
  return $ret
end

I'm not sure what this function does, but it seems to get executed every time the fish_prompt is shown, which causes indeed performance problems. Would it maybe be enough to just listen to "--on-variable PWD" which would cause it to be executed every time the working directory changes?

best,
jochen

[wolph]

Not just on fish, it's very slow with zsh as well.

It takes 100ms for every line you type in your shell...

[ian-h-chamberlain]

Based on #45 and this issue, I modified my config.fish by adding "manual initialization" instead of calling virtualenv-init by default, like so:

pyenv virtualenv-init - fish >> ~/.config/fish/config.fish

Then replacing --on-event fish_prompt with --on-variable PWD --on-variable PYENV_VERSION.

This greatly improves my feedback loop between prompts for most cases, and at least I only have to pay the pyenv-virtualenv penalty when explicitly setting PYENV_VERSION or changing directories. Would it make sense to upstream these changes (perhaps along with a fish_postexec hook that looks for the pyenv shell etc. commands like mentioned in #45 (comment)) ?

[native-api]

pyenv/pyenv#3411 has an example of a profiling technique to find hot spots in Bash code

[native-api]

#523

[jakelodwick]

Fixed in v1.3.0 via #523. The hook now caches the active version using stat checks instead of calling activate on every prompt. The fix includes a full fish implementation alongside bash and zsh.

@ian-h-chamberlain's workaround of triggering the hook on --on-variable PWD instead of fish_prompt helped people in the interim and informed the approach in the fish path of the fix.

[vedal]

Great job @jakelodwick, thanks alot for the effort! :)