Fix route option removal to differ from no changes at all

Author: tas-runtime-bot

app/models/runtime/route.rb

@@ -74,8 +74,9 @@ def options_with_serialization=(opts)
       cleaned_opts = remove_hash_options_for_non_hash_loadbalancing(opts)
       rounded_opts = round_hash_balance_to_one_decimal(cleaned_opts)
       normalized_opts = normalize_hash_balance_to_string(rounded_opts)
-      # Remove nil values after all processing
-      normalized_opts = normalized_opts.compact if normalized_opts.is_a?(Hash)
+      # Convert nil values to empty strings to signal explicit removal to downstream consumers (e.g. gorouter),
+      # so they can distinguish "option was explicitly removed" from "option was never set".
+      normalized_opts = normalized_opts.transform_values { |v| v.nil? ? '' : v } if normalized_opts.is_a?(Hash)
       self.options_without_serialization = Oj.dump(normalized_opts)
     end
 

spec/unit/actions/manifest_route_update_spec.rb

@@ -650,8 +650,7 @@ module VCAP::CloudController
             ManifestRouteUpdate.update(app.guid, message, user_audit_info)
 
             route.reload
-            expect(route.options).to eq({})
-            expect(route.options).not_to have_key('loadbalancing')
+            expect(route.options).to eq({ 'loadbalancing' => '' })
             expect(route.options).not_to have_key('hash_header')
             expect(route.options).not_to have_key('hash_balance')
           end

spec/unit/actions/route_update_spec.rb

@@ -209,7 +209,7 @@ module VCAP::CloudController
             expect(message).to be_valid
             subject.update(route:, message:)
             route.reload
-            expect(route.options).to eq({})
+            expect(route.options).to eq({ 'loadbalancing' => '' })
           end
 
           it 'notifies the backend' do
@@ -299,7 +299,7 @@ module VCAP::CloudController
             subject.update(route:, message:)
             route.reload
             expect(route.options).to include({ 'loadbalancing' => 'hash', 'hash_header' => 'foobar' })
-            expect(route.options).not_to have_key('hash_balance')
+            expect(route.options['hash_balance']).to eq('')
           end
 
           it 'notifies the backend' do
@@ -502,7 +502,7 @@ module VCAP::CloudController
             expect(message).to be_valid
             subject.update(route:, message:)
             route.reload
-            expect(route.options).to eq({})
+            expect(route.options).to eq({ 'loadbalancing' => '' })
           end
 
           it 'notifies the backend' do