Changes from Bash to Zsh Completion Script

This document outlines the changes made to adapt mvnd-bash-completion.bash for zsh compatibility in mvnd-bash+zsh-completion.sh. These changes enable the same completion script to work in both bash and zsh shells.

Overview

The zsh version of the completion script maintains backward compatibility with bash while adding zsh-specific enhancements. The script auto-detects the shell type and applies the appropriate behavior.

Key Changes

1. Shell Detection

A new shell detection mechanism was added at the beginning of the script:

if [ -n "$ZSH_VERSION" ]; then
    __MVND_SHELL="zsh"
elif [ -n "$BASH_VERSION" ]; then
    __MVND_SHELL="bash"
else
    __MVND_SHELL="unknown"
fi

This allows the script to conditionally execute shell-specific code paths.

2. Zsh Completion System Initialization

A new block initializes the zsh completion system and enables bash compatibility mode:

if __is_zsh; then
    # Enable bash compatibility
    autoload -Uz compinit
    compinit -u 2>/dev/null

    # Load bashcompinit for bash-style completions
    autoload -Uz bashcompinit
    bashcompinit

    # Set options for better compatibility
    setopt NO_BEEP
    setopt COMPLETE_IN_WORD
    setopt ALWAYS_TO_END

    # Define COMP_WORDBREAKS if not set (bash compatibility)
    [[ -z "$COMP_WORDBREAKS" ]] && COMP_WORDBREAKS=$' \t\n"\'><=;|&(:'
fi

# Check if the current shell is zsh
__is_zsh()
{
    [ "$__MVND_SHELL" = "zsh" ]
}

Key components:

• compinit - Initializes zsh's completion system
• bashcompinit - Enables bash-style completion functions (complete, compgen, COMPREPLY)
• setopt - Sets zsh options for improved completion behavior
• COMP_WORDBREAKS - Defines word break characters (bash sets this automatically)

3. Function Existence Check

The function_exists function was modified to handle both shells:

Zsh uses typeset instead of declare for function introspection. The 2>&1 redirect suppresses potential error messages.

4. Variable Listing for Plugin Discovery

The common_plugins variable discovery was updated:

• Bash uses compgen -v to list all variable names
• Zsh uses typeset + to list variable names (the + modifier shows only names)

5. Indirect Variable Expansion

When accessing plugin goals dynamically by variable name, different syntax is required:

• Bash uses ${!var_name} for indirect expansion (dereference)
• Zsh uses ${(P)var_name} - the (P) flag enables parameter name expansion

The updated code:

local var_value
if [ "$__MVND_SHELL" = "zsh" ]; then
    var_value="${(P)var_name}"
else
    var_value="${!var_name}"
fi
COMPREPLY=( $(compgen -W "${var_value}" -S ' ' -- ${cur}) )

Summary of Shell Differences

Usage

The script works automatically in both shells. Simply source it in your shell configuration:

# In ~/.bashrc or ~/.zshrc
source /path/to/mvnd-bash+zsh-completion.sh