Remove graphql_resolver_complexity flag

Resolver complexity was enabled on gitlab.com and behaved stable.

app/graphql/types/base_field.rb

@@ -90,8 +90,6 @@ module Types
       # proc because we set complexity depending on arguments and number of
       # items which can be loaded.
       proc do |ctx, args, child_complexity|
-        next base_complexity unless resolver_complexity_enabled?(ctx)
-
         # Resolvers may add extra complexity depending on used arguments
         complexity = child_complexity + self.resolver&.try(:resolver_complexity, args, child_complexity: child_complexity).to_i
         complexity += 1 if calls_gitaly?
@@ -101,10 +99,6 @@ module Types
       end
     end
 
-    def resolver_complexity_enabled?(ctx)
-      ctx.fetch(:graphql_resolver_complexity_flag) { |key| ctx[key] = Feature.enabled?(:graphql_resolver_complexity) }
-    end
-
     def connection_complexity_multiplier(ctx, args)
       # Resolvers may add extra complexity depending on number of items being loaded.
       field_defn = to_graphql

changelogs/unreleased/graphql-complexity-flag.yml

+---
+title: Fix processing of GrapqhQL query complexity based on used resolvers.
+merge_request: 27652
+author:
+type: fixed

spec/graphql/types/base_field_spec.rb

@@ -67,17 +67,6 @@ describe Types::BaseField do
           expect(field.to_graphql.complexity.call({}, { first: 1 }, 2)).to eq 2
           expect(field.to_graphql.complexity.call({}, { first: 1, foo: true }, 2)).to eq 4
         end
-
-        context 'when graphql_resolver_complexity is disabled' do
-          before do
-            stub_feature_flags(graphql_resolver_complexity: false)
-          end
-
-          it 'sets default field complexity' do
-            expect(field.to_graphql.complexity.call({}, {}, 2)).to eq 1
-            expect(field.to_graphql.complexity.call({}, { first: 50 }, 2)).to eq 1
-          end
-        end
       end
 
       context 'and is not a connection' do

spec/requests/api/graphql_spec.rb

@@ -165,7 +165,6 @@ describe 'GraphQL' do
 
     before do
       stub_const('GitlabSchema::DEFAULT_MAX_COMPLEXITY', 6)
-      stub_feature_flags(graphql_resolver_complexity: true)
     end
 
     context 'when fetching single resource' do
@@ -186,18 +185,6 @@ describe 'GraphQL' do
 
         expect_graphql_errors_to_include(/which exceeds max complexity/)
       end
-
-      context 'when graphql_resolver_complexity is disabled' do
-        before do
-          stub_feature_flags(graphql_resolver_complexity: false)
-        end
-
-        it 'processes the query' do
-          post_graphql(query)
-
-          expect(graphql_errors).to be_nil
-        end
-      end
     end
   end
 end