Completely - Bash Completions Generator

Completely is a command line utility and a Ruby library that lets you generate bash completion scripts from simple YAML configuration.

This tool is for you if:

1. You develop your own command line tools.
2. Your life feels empty without bash completions.
3. Bash completion scripts seem overly complex to you.

Note that if you are building bash command line scripts with bashly, then this functionality is already integrated with it.

$ gem install completely

or with homebrew:

$ brew install brew-gem
$ brew gem install completely

or with Docker:

$ alias completely='docker run --rm -it --user $(id -u):$(id -g) --volume "$PWD:/app" dannyben/completely'

Completely works with a simple YAML configuration file as input, and generates a bash completions script as output.

The configuration file is built of blocks that look like this:

pattern:
- --argument
- --param
- command

Each pattern contains an array of words (or functions) that will be suggested for the auto complete process.

You can save a sample YAML file by running:

$ completely init

This will generate a file named completely.yaml with this content:

mygit:
- -h
- -v
- --help
- --version
- init
- status

mygit init:
- --bare
- <directory>

mygit status:
- --help
- --verbose
- --branch
- -b

mygit status*--branch: &branches
- $(git branch --format='%(refname:short)' 2>/dev/null)

mygit status*-b: *branches

Each pattern in this configuration file will be checked against the user's input, and if the input matches the pattern, the list that follows it will be suggested as completions.

Note that the suggested completions will not show flags (strings that start with a hyphen -) unless the input ends with a hyphen.

To generate the bash script, simply run:

$ completely generate

# or, to just preview it without saving:
$ completely preview

For more options (like setting input/output path), run:

$ completely --help

In addition to specifying a simple array of completion words, you may use the special syntax <..> to suggest more advanced functions.

pattern:
- <file>
- <directory>

These suggestions will add the list of files and directories (when <file> is used) or just directories (when <directory> is used) to the list of suggestions.

You may use any of the below keywords to add additional suggestions:

For those interested in the technical details, any word between <...> will simply be added using the compgen -A action function, so you can in fact use any of its supported arguments.

You can also use any command that outputs a whitespace-delimited list as a suggestions list, by wrapping it in $(..). For example, in order to add git branches to your suggestions, use the following:

mygit:
- $(git branch --format='%(refname:short)' 2>/dev/null)

The 2> /dev/null is used so that if the command is executed in a directory without a git repository, it will still behave as expected.

Adding a * wildcard in the middle of a pattern can be useful for suggesting arguments for flags. For example:

mygit checkout:
- --branch
- -b

mygit checkout*--branch:
- $(git branch --format='%(refname:short)' 2>/dev/null)

mygit checkout*-b:
- $(git branch --format='%(refname:short)' 2>/dev/null)

The above will suggest git branches for commands that end with -b or --branch. To avoid code duplication, you may use YAML aliases, so the above can also be written like this:

mygit checkout:
- --branch
- -b

mygit checkout*--branch: &branches
- $(git branch --format='%(refname:short)' 2>/dev/null)

mygit checkout*-b: *branches

Completely also supports an alternative nested syntax. You can generate this example by running:

$ completely init --nested

The example configuration below will generate the exact same script as the one shown at the beginning of this document.

mygit:
- -h
- -v
- --help
- --version
- init:
  - --bare
  - <directory>
- status:
  - --help
  - --verbose
  - +--branch: &branches
    - $(git branch --format='%(refname:short)' 2>/dev/null)
  - +-b: *branches

The rules here are as follows:

• Each pattern (e.g., mygit) can have a mixed array of strings and hashes.
• Strings and hash keys (e.e., --help and init respectively) will be used as completion strings for that pattern.
• Hashes may contain a nested mixed array of the same structure.
• When a hash is provided, the hash key will be appended to the parent prefix. In the example above, the init hash will create the pattern mygit init.
• In order to provide a wildcard (like mygit status*--branch in the standard configuration syntax), you can provide either a * or a + prefix to the hash key (e.g., +--branch or "*--branch"). Note that when using a *, the hash key must be quoted since asterisks have special meaning in YAML.

In order to enable the completions, simply source the generated script:

$ source completely.bash

If you are satisfied with the result, and wish to copy the script to your bash completions directory, simply run:

$ completely install

Alternatively, you can copy the script manually to one of these directories (whichever exists):

• /usr/share/bash-completion/completions
• /usr/local/etc/bash_completion.d
• ~/.local/share/bash-completion/completions

You can use the built in completions script tester by running completely test.

This command lets you test completions for your completions script.

In addition, you can set the COMPLETELY_DEBUG environment variable to any value in order to generate scripts with some additional debugging functionality. Run completely generate --help for additional information.

require 'completely'

# Load from file
completions = Completely::Completions.load "input.yaml"

# Or, from a hash
input = {
  "mygit" => %w[--help --version status init commit],
  "mygit status" => %w[--help --verbose --branch]
}
completions = Completely::Completions.new input

# Generate the script
puts completions.script

# Or, generate a function that echos the script
puts completions.wrapper_function
puts completions.wrapper_function "custom_function_name"

# Or, test the completions with the Tester object
p completions.tester.test "mygit status "

If you are using Oh-My-Zsh, bash completions should already be enabled, otherwise, you should enable completion by adding this to your ~/.zshrc (if is it not already there):

# Load completion functions
autoload -Uz +X compinit && compinit
autoload -Uz +X bashcompinit && bashcompinit

If you experience any issue, have a question or a suggestion, or if you wish to contribute, feel free to open an issue.