venv.fish - Automatically activate/deactivate virtualenv in fish shell

venv.fish

# Based on https://gist.github.com/bastibe/c0950e463ffdfdfada7adf149ae77c6f
# Changes:
# * Instead of overriding cd, we detect directory change. This allows the script to work
#   for other means of cd, such as z.
# * Update syntax to work with new versions of fish.
# * Handle virtualenvs that are not located in the root of a git directory.

function __auto_source_venv --on-variable PWD --description "Activate/Deactivate virtualenv on directory change"
  status --is-command-substitution; and return

  # Check if we are inside a git directory
  if git rev-parse --show-toplevel &>/dev/null
    set gitdir (realpath (git rev-parse --show-toplevel))
    set cwd (pwd -P)
    # While we are still inside the git directory, find the closest
    # virtualenv starting from the current directory.
    while string match "$gitdir*" "$cwd" &>/dev/null
      if test -e "$cwd/.venv/bin/activate.fish"
        source "$cwd/.venv/bin/activate.fish" &>/dev/null 
        return
      else
        set cwd (path dirname "$cwd")
      end
    end
  end
  # If virtualenv activated but we are not in a git directory, deactivate.
  if test -n "$VIRTUAL_ENV"
    deactivate
  end
end

I have packaged this into a fisher plugin: https://github.com/nakulj/auto-venv

Stunning!👍🏻

Thanks for this!

If you call __auto_source_venv at the end of this script, your environment will also be activated when you open a shell in a Python project directory directly.

MacOS users - you might want to update to the latest version if your project resides in a location with uppercase directory names.

-    set cwd (pwd)
+    set cwd (pwd -P)

MacOS has a case insensitive file system where pwd (with the default -L/--logical flag) returns a path with lowercase directory names which causes issues with the case sensitive output of git --rev-parse.