kahmi-dsl

Kahmi is a build system and DSL for Python heavily inspired by Groovy and Gradle. The kahmi-dsl package implements the parser and transpiler for the Kahmi language.

Syntax

The Kahmi DSL might look familar to you if you have used Groovy before. While not any Python code is valid Kahmi DSL code, the full Python language is supported in various places. Additionally, Kahmi DSL allows you to define multi-line lambdas inline with full Python code.

Every Kahmi file starts with a "context" object. There are four main syntactical elements that are supported by the Kahmi language:

• let definitions for local variables
• member assignments to the current context
• calls and call blocks
• Python expressions (with multi-line lambda support)

let re = __import__('re')

msg = "Hello, World!"

print(re.sub(r'[,!]', '', self.msg))  # prints: Hello World

re.sub(r'[A-z ]', '', self.msg) {
  print(self)  # prints: ,!
}

You can transpile it into Python code to see what's going on under the hood:

$ python -m kahmi.dsl build.kahmi   -E
re = __import__('re')
self.msg = 'Hello, World!'
__lookup__('print', locals(), self)(re.sub('[,!]', '', self.msg))


def __call_re_sub(self):
    __lookup__('print', locals(), self)(self)


value = __lookup__('re', locals(), self).sub('[A-z ]', '', self.msg)
__call_re_sub(value)

What you see as self here is the current "context" object and __lookup__() is a helper that allows you to call local variables, members of the context or builtins.

Lambdas

Lambdas are implemented by placing function definitions for you before they are used. Lambdas can be nested and they are properly taking the right scope in most cases (exceptions are Python expressions that introduce a new scope like generator, tuple, list, set and dict comprehensions).

let myFunc = () => {
  return name => { return f'Hello, {name}' }
}

myFunc() {
  print(self('Sam'))  # prints: Hello, Sam
}

Again, transpiling into pure Python code help to understand what is going on:

ef lambda_build_kahmi_1_13():

    def lambda_build_kahmi_2_8(name):
        return f'Hello, {name!r}'
    return lambda_build_kahmi_2_8


myFunc = lambda_build_kahmi_1_13


def __call_myFunc(self):
    __lookup__('print', locals(), self)(self('Sam'))


value = __lookup__('myFunc', locals(), self)()
__call_myFunc(value)

CLI

The command-line interface for the kahmi-dsl package is very simplistic. It is not expected that it provides much value outside of development as it only provides a limited method of building and passing the root context object to the script.

usage: python -m kahmi.dsl [-h] [-c ENTRYPOINT] [-E] [file]

positional arguments:
  file

optional arguments:
  -h, --help            show this help message and exit
  -c ENTRYPOINT, --context ENTRYPOINT
  -E, --transpile

If no -c,--context is provided a kahmi.dsl.__main__.VoidContext object is used which is really just an instance of an empty class.

Copyright © 2021 Niklas Rosenstein