Developing builtin kittens

Builtin kittens in kitty are written in the Go language, with small Python wrapper scripts to define command line options and handle UI integration.

Getting started

To get started with creating a builtin kitten, one that will become part of kitty and be available as kitten my-kitten, create a directory named my_kitten in the kittens directory. Then, in this directory add three, files: __init__.py (an empty file), __main__.py and main.go.

Template for main.py

The file main.py contains the command line option definitions for your kitten. Change the actual options and help text below as needed.

#!/usr/bin/env python
# License: GPL v3 Copyright: 2018, Kovid Goyal <kovid at kovidgoyal.net>

import sys

# See the file kitty/cli.py in the kitty sourcecode for more examples of
# the syntax for defining options
OPTIONS = r'''
--some-string-option -s
default=my_default_value
Help text for a simple option taking a string value.


--some-boolean-option -b
type=bool-set
Help text for a boolean option defaulting to false.


--some-inverted-boolean-option
type=bool-unset
Help text for a boolean option defaulting to true.


--an-integer-option
type=int
default=13
bla bla


--an-enum-option
choices=a,b,c,d
default=a
This option can only take the values a, b, c, or d
'''.format

help_text = '''\
The introductory help text for your kitten.

Can contain multiple paragraphs with :bold:`bold`
:green:`colored`, :code:`code`, :link:`links <http://url>` etc.
formatting.

Option help strings can also use this formatting.
'''

# The usage string for your kitten
usage = 'TITLE [BODY ...]'
short_description = 'some short description of your kitten it will show up when running kitten without arguments to list all kittens`

if __name__ == '__main__':
    raise SystemExit('This should be run as kitten my-kitten')
elif __name__ == '__doc__':
    cd = sys.cli_docs  # type: ignore
    cd['usage'] = usage
    cd['options'] = OPTIONS
    cd['help_text'] = help_text
    cd['short_desc'] = short_description

Template for main.go

package my_kitten

import (
    "fmt"

    "kitty/tools/cli"
)

var _ = fmt.Print

func main(_ *cli.Command, opts *Options, args []string) (rc int, err error) {
    // Here rc is the exit code for the kitten which should be 1 or higher if err is not nil
    fmt.Println("Hello world!")
    fmt.Println(args)
    fmt.Println(fmt.Sprintf("%#v", opts))
    return
}

func EntryPoint(parent *cli.Command) {
    create_cmd(parent, main)
}

Edit tools/cmd/tool/main.go

Add the entry point of the kitten into tools/cmd/tool/main.go.

First, import the kitten into this file. To do this, add "kitty/kittens/my_kitten" into the import ( ... ) section at the top. Then, add my_kitten.EntryPoint(root) into func KittyToolEntryPoints(root *cli.Command) and you are done. After running make you should be able to test your kitten by running:

kitten my-kitten