Fix given_or_derived behavior in Pops Object initialization

The PCore specification states "The given_or_derived
attribute kind states that if the attribute is given
when the object is instantiated this value is used,
otherwise it is a computed value." and "It is
allowed to give the value when instantiating in
which case the given value overrides what would
be the computed value."

The current implementation treats an attribute
with the kind given_or_derived as a required
parameter during initialization (in the
init_hash used in from_asserted_hash or in the
generated `initialize` method).

This change enforces an implicit `value` parameter
of `nil` which causes the generated init_hash
type check and the generated initialize method
to treat given_or_derived attributes as optional.

Author: seanmil

lib/puppet/pops/types/p_object_type.rb

@@ -316,6 +316,8 @@ def initialize(name, container, init_hash)
 
         v = init_hash[KEY_VALUE]
         @value = v == :default ? v : TypeAsserter.assert_instance_of(nil, type, v) { "#{label} #{KEY_VALUE}" }
+      elsif @kind == ATTRIBUTE_KIND_GIVEN_OR_DERIVED
+        @value = nil
       else
         raise Puppet::ParseError, _("%{label} of kind 'constant' requires a value") % { label: label } if @kind == ATTRIBUTE_KIND_CONSTANT
 
@@ -341,7 +343,7 @@ def _pcore_init_hash
         hash[KEY_KIND] = @kind
         hash.delete(KEY_FINAL) if @kind == ATTRIBUTE_KIND_CONSTANT # final is implied
       end
-      hash[KEY_VALUE] = @value unless @value == :undef
+      hash[KEY_VALUE] = @value unless @value == :undef || @kind == ATTRIBUTE_KIND_GIVEN_OR_DERIVED
       hash
     end
 

spec/unit/pops/types/p_object_type_spec.rb

@@ -697,31 +697,31 @@ def parse_object(name, body_string)
   end
 
   context 'when producing an init_hash_type' do
-    it 'produces a struct of all attributes that are not derived or constant' do
+    it 'produces a struct of all attributes excepting derived or constant' do
       t = parse_object('MyObject', <<-OBJECT)
         attributes => {
           a => { type => Integer },
-          b => { type => Integer, kind => given_or_derived },
-          c => { type => Integer, kind => derived },
-          d => { type => Integer, kind => constant, value => 4 }
+          b => { type => Integer, kind => derived },
+          c => { type => Integer, kind => constant, value => 4 }
         }
       OBJECT
       expect(t.init_hash_type).to eql(factory.struct({
         'a' => factory.integer,
-        'b' => factory.integer
       }))
     end
 
     it 'produces a struct where optional entires are denoted with an optional key' do
       t = parse_object('MyObject', <<-OBJECT)
         attributes => {
           a => { type => Integer },
-          b => { type => Integer, value => 4 }
+          b => { type => Integer, value => 4 },
+          c => { type => Integer, kind => given_or_derived },
         }
       OBJECT
       expect(t.init_hash_type).to eql(factory.struct({
         'a' => factory.integer,
-        factory.optional('b') => factory.integer
+        factory.optional('b') => factory.integer,
+        factory.optional('c') => factory.integer,
       }))
     end