isabella232 / layer-options

Library for reading layer options for charms

Overview

This base layer provides a function to read options defined in layer.yaml file. The options can be specified in multiple sections, generally one per layer included in the final built charm. Each layer can define what options it can accept in the same format that action parameters are defined: jsonschema.

Usage

Suppose layer foo specifies the following option definitions in its layer.yaml:

defines:
  my_opt_1:
    description: A numerical option.
    type: number
    default: 1
  my_opt_a:
    description: An array option.
    type: array
    default: []
  my_opt_b:
    description: A boolean option.
    type: boolean
    default: false

A layer including it could specify values for these options in its own layer.yaml:

options:
  foo:
    my_opt_1: 2
    my_opt_a: ['a', 'b']
    my_opt_b: true

The foo layer could then read these values in its reactive code:

from charms import layer
from charms.reactive import when_not, set_flag


@when_not('layer.foo.done')
def do_foo():
    foo_opts = layer.options.get('foo')  # returns a dict of all the options
    my_opt_1 = layer.options.get('foo', 'my_opt_1')  # returns just that option
    do_something_with(foo_opts)
    set_flag('layer.foo.done')