Aliases for attributes

Use Case

Sometimes, for backwards compatibility prior to deprecation, it would be useful to change an attribute's name but retain an alias to the old/alternate name. Similarly, sometimes the parameters for the underlying object being managed itself have aliases which should be usable at the Puppet resource level.

Describe the Solution You Would Like

A new optional key for attributes called aliases which takes one ore more symbols as alternate names. For example:

Puppet::ResourceApi.register_type(
  name: 'testy_resource',
  docs: 'test resource',
  attributes: {
    ensure: {
      type:    'Enum[present, absent]',
      desc:    'Whether this resource should be present or absent on the target system.',
      default: 'present',
    },
    name: {
      type:      'String',
      desc:      'Description of the purpose for this resource declaration.',
      behaviour: :namevar,
    },
    foo: {
      type:      'String',
      desc:      'Description of the purpose for this resource declaration.',
      aliases: [:bar, :baz],
    },
)

Which would then have the following equivalent manifest declarations:

testy_resource { 'some title':
  foo => 'bing!',
}

testy_resource { 'some title':
  bar => 'bing!',
}

testy_resource { 'some title':
  baz => 'bing!',
}

But would fail if you tried to specify either the same attribute, regardless of name/alias, twice in the same resource:

testy_resource { 'some title':
  foo => 'boop!',
  bar => 'woop!',
}

Start at Puppet::ResourceApi.register_type and trace how attribute definitions are validated and exposed to resource declarations. Define completion as aliases accepting equivalent names while rejecting duplicate canonical or alias names in one resource, then verify the documented examples and failure case.