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README.md

click-completion

Enhanced completion for Click

Add automatic completion support for fish, Zsh, Bash and PowerShell to Click.

All the supported shells are able to complete all the command line arguments and options defined with click. In addition, fish and Zsh are also displaying the options and commands help during the completion.

asciicast

Activation

In order to activate the completion, you need to:

  • initialize the click_completion module;
  • inform your shell that completion is available for your script, and how.

click_completion initialization

click_completion monkey-patches click in order to enhance the native completion capabilities. This is done very simply:

import click_completion
click_completion.init()

Once done, your click application is ready for completion.

Inform your shell

click_completion has some functions to produce the code to be executed by the shell during the completion, and to permanently install this code in a place that is automatically loaded by the shell.

The key functions are:

  • get_code
  • install

An example of usage can be found in examples/click-completion-command and in examples/click-completion-callback

Dependencies

click-completion obviously depends on click. Jinja2 is used to generate the shell specific code.

And of course to make it useful, you'll need to use fish, Bash, Zsh or PowerShell.

Customizing completion

Application level

click_complete has a startswith function that can be replaced by a custom one in order to customize the completion. Some extra environment variable to be used during the completion can be passed to get_code and install. An example is available in examples/click-completion-command.

Parameter type level

The custom parameter type may reimplement the complete method in order to customize the completion result. The complete method takes the current context and the incomplete argument to be completed. It can return either a list of argument value that match the incomplete argument, or a list of tuples (arg, help). This last form is preferred because it allows to display the help during the completion for the shells that supports it.

An example can be found in the class DocumentedChoice in click_completion/init.py.

How it works

As click, the general way click_completion works is through a magic environment variable called _<PROG_NAME>_COMPLETE, where <PROG_NAME> is your application executable name in uppercase with dashes replaced by underscores.

If your tool is called foo-bar, then the magic variable is called _FOO_BAR_COMPLETE. By exporting it with the source value it will spit out the activation script which can be trivially activated.

For instance, to enable fish completion for your foo-bar script, this is what you would need to put into your ~/.config/fish/completions/foo-bar.fish

eval (env _FOO_BAR_COMPLETE=source-fish foo-bar)

From this point onwards, your script will have fish completion enabled.

The above activation example will always invoke your application on startup. This might be slowing down the shell activation time significantly if you have many applications. Alternatively, you could also ship a file with the contents of that, which is what Git and other systems are doing.

This can be easily accomplished:

_FOO_BAR_COMPLETE=source-fish foo-bar > ~/.config/fish/completions/foo-bar.fish

License

Licensed under the MIT, see LICENSE.

Contributing

Contributions are all very welcome!

This may be in the form of bug reports, pull requests, …

A few subjects need some attention currently:

  • documentation
  • tests
  • argument parsing
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