(PDK-884) Handle missing namevars returned by providers

lib/puppet/resource_api.rb

@@ -200,6 +200,9 @@ def feature_support?(feature)
             property = definition[:attributes][key.first]
             attr_def[key.first] = property
           end
+          if resource_hash[namevar_name].nil?
+            raise Puppet::ResourceError, "`#{name}.get` did not return a value for the `#{namevar_name}` namevar attribute"
+          end
           Puppet::ResourceApi::TypeShim.new(resource_hash[namevar_name], resource_hash, name, namevar_name, attr_def)
         end
       end

spec/fixtures/test_module/lib/puppet/provider/title_provider/title_provider.rb

@@ -6,11 +6,11 @@ class Puppet::Provider::TitleProvider::TitleProvider < Puppet::ResourceApi::Simp
   def get(_context)
     [
       {
-        name: 'foo',
+        namevar: 'foo',
         ensure: :present,
       },
       {
-        name: 'bar',
+        namevar: 'bar',
         ensure: :present,
       },
     ]

spec/puppet/resource_api_spec.rb

@@ -471,6 +471,31 @@ def extract_values(function)
         it('the namevar is set to the name') { expect(instance[:not_name]).to eq 'test' }
       end
     end
+
+    describe 'a provider that does not return the namevar', agent_test: true do
+      subject(:instance) { Puppet::Type.type(:not_name_namevar) }
+
+      let(:provider_class) do
+        Class.new do
+          def get(_context)
+            [{ name: 'some title' }]
+          end
+
+          def set(_context, changes) end
+        end
+      end
+
+      before(:each) do
+        stub_const('Puppet::Provider::NotNameNamevar', Module.new)
+        stub_const('Puppet::Provider::NotNameNamevar::NotNameNamevar', provider_class)
+      end
+
+      it('throws an error') {
+        expect {
+          instance.instances
+        }.to  raise_error Puppet::ResourceError, %r{^`not_name_namevar.get` did not return a value for the `not_name` namevar attribute$}
+      }
+    end
   end
 
   describe '#load_provider', agent_test: true do