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