Repository: pypa/pip
File: src/pip/_internal/commands/completion.py (Python)

Code before:
                           COMP_CWORD=$COMP_CWORD \\
                           PIP_AUTO_COMPLETE=1 $1 2>/dev/null ) )
        }}
        complete -o default -F _pip_completion {prog}
    """,
    'zsh': """
        function _pip_completion {{
          local words cword
          read -Ac words
          read -cn cword
          reply=( $( COMP_WORDS="$words[*]" \\
                     COMP_CWORD=$(( cword-1 )) \\
                     PIP_AUTO_COMPLETE=1 $words[1] 2>/dev/null ))
        }}
        compctl -K _pip_completion {prog}
    """,
    'fish': """
        function __fish_complete_pip
            set -lx COMP_WORDS (commandline -opc) (commandline -ct)
            set -lx COMP_CWORD (math (count $COMP_WORDS) - 1)
            set -lx PIP_AUTO_COMPLETE 1
            string split \\  -- (eval $COMP_WORDS[1])
        end
        complete -fa "(__fish_complete_pip)" -c {prog}
    """,
}


class CompletionCommand(Command):
    """A helper command to be used for command completion."""

    ignore_require_venv = True

    def add_options(self):
        # type: () -> None
        self.cmd_opts.add_option(
            '--bash', '-b',
            action='store_const',
            const='bash',
            dest='shell',
            help='Emit completion code for bash')
        self.cmd_opts.add_option(
            '--zsh', '-z',
            action='store_const',
            const='zsh',
            dest='shell',
            help='Emit completion code for zsh')
        self.cmd_opts.add_option(
            '--fish', '-f',
            action='store_const',
            const='fish',

Review comment (suggestion):
Hah, I was drafting a similar PR last night. Can I suggest changing to the long options? It makes it much clearer for people not familiar with fish.

Code after:
                           COMP_CWORD=$COMP_CWORD \\
                           PIP_AUTO_COMPLETE=1 $1 2>/dev/null ) )
        }}
        complete -o default -F _pip_completion {prog}
    """,
    "zsh": """
        #compdef -P pip[0-9.]#
        __pip() {{
          compadd $( COMP_WORDS="$words[*]" \\
                     COMP_CWORD=$((CURRENT-1)) \\
                     PIP_AUTO_COMPLETE=1 $words[1] 2>/dev/null )
        }}
        if [[ $zsh_eval_context[-1] == loadautofunc ]]; then
          # autoload from fpath, call function directly
          __pip "$@"
        else
          # eval/source/. command, register function for later
          compdef __pip -P 'pip[0-9.]#'
        fi
    """,
    "fish": """
        function __fish_complete_pip
            set -lx COMP_WORDS \\
                (commandline --current-process --tokenize --cut-at-cursor) \\
                (commandline --current-token --cut-at-cursor)
            set -lx COMP_CWORD (math (count $COMP_WORDS) - 1)
            set -lx PIP_AUTO_COMPLETE 1
            set -l completions
            if string match -q '2.*' $version
                set completions (eval $COMP_WORDS[1])
            else
                set completions ($COMP_WORDS[1])
            end
            string split \\  -- $completions
        end
        complete -fa "(__fish_complete_pip)" -c {prog}
    """,
    "powershell": """
        if ((Test-Path Function:\\TabExpansion) -and -not `
            (Test-Path Function:\\_pip_completeBackup)) {{
            Rename-Item Function:\\TabExpansion _pip_completeBackup
        }}
        function TabExpansion($line, $lastWord) {{
            $lastBlock = [regex]::Split($line, '[|;]')[-1].TrimStart()
            if ($lastBlock.StartsWith("{prog} ")) {{
                $Env:COMP_WORDS=$lastBlock
                $Env:COMP_CWORD=$lastBlock.Split().Length - 1
                $Env:PIP_AUTO_COMPLETE=1
                (& {prog}).Split()
                Remove-Item Env:COMP_WORDS
                Remove-Item Env:COMP_CWORD