completions

name	completions
description	ZSH completion system patterns and conventions. Use when implementing custom completion handling, writing completion files, or working with zsh autocomplete. Do not use when installing packages from homebrew, since that typically installs completions automatically.
allowed-tools	["Read","Write","Edit","Bash","Grep","Glob"]

Completions

Guide for writing and managing custom ZSH completion files in this dotfiles repository.

When to Use

• Implementing custom completions for CLI tools
• Fixing or updating existing completion files
• Understanding how completions are loaded in this repo

Do NOT use when installing homebrew packages - they handle completions automatically.

Repository Conventions

File Naming

Completion files in this repo use: <topic>/completion.zsh

Example: claude/completion.zsh

Loading Process

From zsh/zshrc:

1. compinit is called to initialize the completion system
2. All */completion.zsh files are sourced
3. Files are sourced directly, NOT added to fpath

File Structure

#!/usr/bin/env zsh

# Define completion function
_toolname() {
  local line state

  # Define options
  local -a options=(
    '-h[Display help]'
    '--help[Display help]'
  )

  # Define subcommands
  local -a subcommands=(
    'command:Description'
  )

  _arguments -C \
    "${options[@]}" \
    '1: :->command' \
    '*::arg:->args'

  case $state in
    command)
      _describe -t commands 'tool command' subcommands
      ;;
    args)
      # Handle subcommand args
      ;;
  esac
}

# Register completion
compdef _toolname toolname

Key Patterns

Registration

Use compdef at the end of the file:

compdef _toolname toolname

NOT the #compdef directive (that's for files in fpath).

Options Format

local -a options=(
  '-h[Display help]'
  '--help[Display help]'
  '--flag[Description]'
  '--option[Description]:value:'
  '--file[Description]:file:_files'
  '--dir[Description]:directory:_directories'
)

Subcommands

local -a subcommands=(
  'command:Description'
  'subcommand:What it does'
)

_describe -t commands 'tool command' subcommands

Argument Handling

_arguments -C \
  "${options[@]}" \
  '1: :->command' \
  '*::arg:->args'

case $state in
  command)
    _describe -t commands 'tool command' subcommands
    ;;
  args)
    case ${line[1]} in
      subcommand)
        _arguments \
          '--subcommand-option[Description]' \
          '1:arg:'
        ;;
    esac
    ;;
esac

Nested Subcommands

For tools like git or docker with deep command hierarchies:

_tool_subcommand() {
  local line state

  local -a sub_subcommands=(
    'action:Description'
  )

  _arguments -C \
    '1: :->command' \
    '*::arg:->args'

  case $state in
    command)
      _describe -t commands 'tool subcommand command' sub_subcommands
      ;;
  esac
}

Common Completers

Built-in zsh completion functions:

• _files - File paths
• _directories - Directory paths
• _values - Predefined values
• _describe - Command descriptions
• _arguments - Argument parsing

File Completion

'--config[Config file]:file:_files'

Choice Completion

'--format[Output format]:format:(json yaml text)'

Multiple Values

'--env[Environment variables]:env:'  # Free form
'--scope[Scope]:scope:(local user project)'  # Fixed choices

Testing

After creating/modifying a completion file:

1. Reload shell: source ~/.zshrc
2. Test completion: tool <TAB>
3. Test subcommands: tool subcommand <TAB>
4. Test options: tool --<TAB>

Generating Completions

Steps to create completions for a new tool:

1. Run tool --help to see main options
2. Run tool subcommand --help for each subcommand
3. Create <topic>/completion.zsh
4. Define _toolname() function with all discovered options
5. Register with compdef _toolname toolname
6. Test thoroughly

Common Issues

"command not found: _arguments"

The completion function is being executed instead of sourced. Ensure:

• File is named completion.zsh (not completions.zsh)
• Using compdef (not #compdef)
• File is in a topic directory that gets sourced

"can only be called from completion function"

Using #compdef directive when file is sourced directly. Use compdef registration instead.

Completions Not Loading

1. Check file naming: */completion.zsh
2. Verify file is being sourced: echo $ZSH/**/*.zsh | grep completion
3. Check for syntax errors: zsh -n path/to/completion.zsh

Examples

See existing completion files:

• claude/completion.zsh - Complex multi-level subcommands
• gcloud/completions.zsh - Third-party completion sourcing