(PDK-887) Add checks for read_only values being set or modified

[da-ar]

No description provided.

[DavidS]

david@davids:~/git/puppet-resource_api$ bundle exec puppet resource --modulepath spec/fixtures/modules/ test_validation 
test_validation { "bar": 
  ensure => 'present',
# prop => 3, # Read Only
}
test_validation { "foo": 
  ensure => 'present',
# prop => 2, # Read Only
}
david@davids:~/git/puppet-resource_api$ bundle exec puppet resource --modulepath spec/fixtures/modules/ test_validation bar param=3
test_validation { 'bar':
  ensure => 'present',
}
david@davids:~/git/puppet-resource_api$ bundle exec puppet resource --modulepath spec/fixtures/modules/ test_validation bar param=3 prop=2
test_validation { 'bar':
  ensure => 'present',
}
david@davids:~/git/puppet-resource_api$ bundle exec puppet resource --modulepath spec/fixtures/modules/ test_validation bar param=3 prop=1
test_validation { 'bar':
  ensure => 'present',
}
david@davids:~/git/puppet-resource_api$ 

The last command definitely should fail (tries to modify prop from 2 to 1). I'm not 100% sure, but the second to last command (setting prop to its current value) should likely fail too: it is not even valid to try to set a read_only value.

[DavidS]

e.g. Azure has https://github.com/puppetlabs/puppetlabs-azure/blob/b30e68b7da9c3c4cb60a303b2e3d3c675579784f/lib/puppet_x/puppetlabs/azure/property/read_only.rb#L5 which already fails on validation. that is, every time someone tries to set any value.