Fix 500 when diffing manifests with metadata

[#174432303]

Co-authored-by: Chris Selzo <cselzo@pivotal.io>
Co-authored-by: Reid Mitchell <rmitchell@pivotal.io>

Author: selzoc

app/actions/space_diff_manifest.rb

@@ -43,14 +43,13 @@ def self.filter_manifest_app_hash(manifest_app_hash)
       end
 
       if manifest_app_hash.key? 'metadata'
-        manifest_app_hash['metadata'] = manifest_app_hash['metadata'].map do |hash|
-          hash.slice(
-            'labels',
-            'annotations'
-          )
-        end
-        manifest_app_hash = manifest_app_hash.except('metadata') if manifest_app_hash['metadata'] == [{}]
+        manifest_app_hash['metadata'] = manifest_app_hash['metadata'].slice(
+          'labels',
+          'annotations'
+        )
+        manifest_app_hash = manifest_app_hash.except('metadata') if manifest_app_hash['metadata'] == {}
       end
+
       manifest_app_hash
     end
 

spec/unit/actions/space_diff_manifest_spec.rb

@@ -73,6 +73,22 @@ module VCAP::CloudController
         end
       end
 
+      context 'metadata is added' do
+        before do
+          default_manifest['applications'][0]['metadata'] = {
+            'labels' => { 'foo' => 'bar' },
+            'annotations' => { 'baz' => 'qux' }
+          }
+        end
+
+        it 'returns the correct diff' do
+          expect(subject).to eq([
+            { 'op' => 'add', 'path' => '/applications/0/metadata/labels/foo', 'value' => 'bar' },
+            { 'op' => 'add', 'path' => '/applications/0/metadata/annotations/baz', 'value' => 'qux' },
+          ])
+        end
+      end
+
       context 'when there is a change inside of a nested hash' do
         before do
           default_manifest['applications'][0]['processes'][0].delete('memory')