Given https://gist.github.com/marcoceppi/ca36655cb917b16d0681 when charm build was run on ubucon it would produce a few artifacts. The first being a .layer.schema file which contains the namespaced schema for each layer's defines (if provided). Then layer.yaml would be the computed merge of all layer.yamls with each layer overwriting the previou…

.layer.schema

basic:
  type: object
  properties:
    packages:
      type: array
      description: apt-packages to install
django:
  type: object
  properties:
    install-path:
      type: string
      default: "/opt"
      description: server install path
    code:
      type: string
      default: "yarg"
      description: source of django application

layer.yaml

includes: ['layer:basic', 'layer:django']
options:
  basic:
    packages:
      - python-dev
      - obama
  django:
    install-path: "/srv"

layerschema.py

import yaml
import jsonschema


with open('layer.yaml') as f:
   layer = yaml.safe_load(f.read())

with open('.layer.schema') as f:
   schema = yaml.safe_load(f.read())

options = layer.get('options', {})

jsonschema.validate(options, schema)

requirements.txt

PyYAML==3.11
argparse==1.2.1
functools32==3.2.3-2
jsonschema==2.5.1
wsgiref==0.1.2

Given https://gist.github.com/marcoceppi/ca36655cb917b16d0681 when charm build was run on ubucon it would produce a few artifacts. The first being a .layer.schema file which contains the namespaced schema for each layer's defines (if provided).

Then layer.yaml would be the computed merge of all layer.yaml files from each layer, with each layer overwriting the previous key (or merging, where applicable). Finally schema validation would be performed against the final build to let the user know if the options are all valid.

Ideally reactive would provide a tool to get the option values as a command to avoid needless parsing of layer.yaml by the user.

Alternatively, instead of stacking everything in layer.yaml an options.yaml file could be created (or .options.yaml to keep safe namespacing) where the options data would be held.

Finally, default key is ignored in jsonschema module. The reasoning makes sense but we'll need to make a clever parser to set defaults for values not defined by an author. All the more reason to have a reactive helper for this.