Optional / mutually exclusive resource parameters with the Puppet Resource API

[Benjamin Ridley]

Hi all, 

I'm developing a resource that allows the declaration of keys in the Etcd key value store. 

My type looks like this:

Puppet::ResourceApi.register_type(
  name: 'etcd_key',
  docs: 'This type allows the management of etcd keys as Puppet resources.',
  attributes: {
    ensure: {
      type: 'Enum[present, absent]',
      desc: 'Whether the key should be present in the etcd structure.',
      default: 'present',
    },
    path: {
      type: 'String',
      desc: 'The path of the key you want to manage in the etcd structure.',
      behaviour: :namevar,
    },
    directory: {
      type: 'Boolean',
      desc: 'Whether this key is a directory or not.',
      default: false,
    },
    value: {
      type: 'String',
      desc: 'The value of the key. Mutually exclusive if with is_directory => true.',
    },
  },
)

What I want to be able to do is make the value/directory parameters mutually exclusive as a directory does not have a 'value' in etcd, and similarly a key with a value cannot be a directory. Currently though, Puppet complains that I'm excluding required parameters when I declare them.

Is this possible with the resource API or do I need to use the low level provider implementation?

Thanks! Ben

[David Schmitt]

Hi Ben,

to avoid having server-side code, the Resource API doesn't have a way to validate complex restrictions like this at compile time. You can either collapse this into a single attribute of type `Variant[Boolean, String]` or adding the validation in the provider at the time `set`/`create`/`update`/`delete` get called. throwing an exception from those methods will tell puppet that the resource application failed and present the exception message to the user.

Regards, David

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[Benjamin Ridley]

Thanks David, I ended up reimplementing with the low level API and just had custom values for the ensure property. Thanks for the help though the Variant method seems like an elegant solution to keep in mind.

Cheers, 

Ben

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