Allow enums to be nullable.

Fixes #37.

lib/interpol/endpoint.rb

@@ -279,7 +279,10 @@ def conditionally_make_nullable(raw_schema)
       types = Array(raw_schema['type'])
       return if types.none? || types.include?('null')
 
-      raw_schema['type'] = (types << "null")
+      # Mark as non-nullable so it doesn't try to recurse down into it
+      # and make it nullable at that level (since we are taking care of it at this level)
+      sub_schema = raw_schema.merge('nullable' => false)
+      raw_schema.replace('type' => ['null', sub_schema])
     end
 
     def should_be_nullable?(raw_schema)

spec/unit/interpol/endpoint_spec.rb

@@ -420,6 +420,28 @@ def new_with(hash)
           expect { subject.validate_data!('foo' => nil) }.not_to raise_error
         end
 
+        it 'works with enums' do
+          schema['properties']['foo'] = {
+            'type' => 'string',
+            'enum' => %w[ A B C D F ]
+          }
+
+          expect { subject.validate_data!('foo' => nil) }.not_to raise_error
+          expect { subject.validate_data!('foo' => 'A') }.not_to raise_error
+          expect { subject.validate_data!('foo' => 'F') }.not_to raise_error
+          expect { subject.validate_data!('foo' => 'E') }.to raise_error(ValidationError)
+        end
+
+        it 'allows enums to be non-nullable' do
+          schema['properties']['foo'] = {
+            'nullable' => false,
+            'type' => 'string',
+            'enum' => %w[ A B C D F ]
+          }
+
+          expect { subject.validate_data!('foo' => nil) }.to raise_error(ValidationError)
+        end
+
         it 'does not add an extra `null` entry to an existing nullable union type' do
           schema['properties']['foo']['type'] = %w[ integer null ]