Add negatve filters for merge requests API

Introduces negative filtering options for
GraphQL API. Can be used in any GraphQL query

app/finders/issuable_finder.rb

@@ -244,7 +244,7 @@ class IssuableFinder
 
         # These are "helper" params that modify the results, like :in and :search. They usually come in at the top-level
         # params, but if they do come in inside the `:not` params, the inner ones should take precedence.
-        not_helpers = params.slice(*NEGATABLE_PARAMS_HELPER_KEYS).merge(params[:not].slice(*NEGATABLE_PARAMS_HELPER_KEYS))
+        not_helpers = params.slice(*NEGATABLE_PARAMS_HELPER_KEYS).merge(params[:not].to_h.slice(*NEGATABLE_PARAMS_HELPER_KEYS))
         not_helpers.each do |key, value|
           not_params[key] = value unless not_params[key].present?
         end

app/graphql/resolvers/merge_requests_resolver.rb

@@ -3,6 +3,7 @@
 module Resolvers
   class MergeRequestsResolver < BaseResolver
     include ResolvesMergeRequests
+    extend ::Gitlab::Graphql::NegatableArguments
 
     type ::Types::MergeRequestType.connection_type, null: true
 
@@ -68,6 +69,16 @@ module Resolvers
              required: false,
              default_value: :created_desc
 
+    negated do
+      argument :labels, [GraphQL::STRING_TYPE],
+               required: false,
+               as: :label_name,
+               description: 'Array of label names. All resolved merge requests will not have these labels.'
+      argument :milestone_title, GraphQL::STRING_TYPE,
+               required: false,
+               description: 'Title of the milestone.'
+    end
+
     def self.single
       ::Resolvers::MergeRequestResolver
     end

changelogs/unreleased/92508-enable-not-filters-for-mr-labels-graphql.yml

+---
+title: Add negative filters for merge requests API
+merge_request: 58021
+author:
+type: added

lib/gitlab/graphql/negatable_arguments.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Graphql
+    module NegatableArguments
+      class TypeDefiner
+        def initialize(resolver_class, type_definition)
+          @resolver_class = resolver_class
+          @type_definition = type_definition
+        end
+
+        def define!
+          negated_params_type.instance_eval(&@type_definition)
+        end
+
+        def negated_params_type
+          @negated_params_type ||= existing_type || build_type
+        end
+
+        private
+
+        def existing_type
+          ::Types.const_get(type_class_name, false) if ::Types.const_defined?(type_class_name)
+        end
+
+        def build_type
+          klass = Class.new(::Types::BaseInputObject)
+          ::Types.const_set(type_class_name, klass)
+          klass
+        end
+
+        def type_class_name
+          @type_class_name ||= begin
+            base_name = @resolver_class.name.sub('Resolvers::', '')
+            base_name + 'NegatedParamsType'
+          end
+        end
+      end
+
+      def negated(param_key: :not, &block)
+        definer = ::Gitlab::Graphql::NegatableArguments::TypeDefiner.new(self, block)
+        definer.define!
+
+        argument param_key, definer.negated_params_type,
+                 required: false,
+                 description: <<~MD
+                     List of negated arguments.
+                     Warning: this argument is experimental and a subject to change in future.
+                 MD
+      end
+    end
+  end
+end

spec/graphql/resolvers/merge_requests_resolver_spec.rb

@@ -189,6 +189,17 @@ RSpec.describe Resolvers::MergeRequestsResolver do
       end
     end
 
+    context 'with negated label argument' do
+      let_it_be(:label) { merge_request_6.labels.first }
+      let_it_be(:with_label) { create(:labeled_merge_request, :closed, labels: [label], **common_attrs) }
+
+      it 'excludes merge requests with given label from selection' do
+        result = resolve_mr(project, not: { labels: [label.title] })
+
+        expect(result).not_to include(merge_request_6, with_label)
+      end
+    end
+
     context 'with merged_after and merged_before arguments' do
       before do
         merge_request_1.metrics.update!(merged_at: 10.days.ago)
@@ -221,6 +232,14 @@ RSpec.describe Resolvers::MergeRequestsResolver do
       end
     end
 
+    context 'with negated milestone argument' do
+      it 'filters out merge requests with given milestone title' do
+        result = resolve_mr(project, not: { milestone_title: milestone.title })
+
+        expect(result).not_to include(merge_request_with_milestone)
+      end
+    end
+
     describe 'combinations' do
       it 'requires all filters' do
         create(:merge_request, :closed, **common_attrs, source_branch: merge_request_4.source_branch)

spec/graphql/types/project_type_spec.rb

@@ -243,6 +243,7 @@ RSpec.describe GitlabSchema.types['Project'] do
                                             :assignee_username,
                                             :reviewer_username,
                                             :milestone_title,
+                                            :not,
                                             :sort
                                            )
     end

spec/lib/gitlab/graphql/negatable_arguments_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Graphql::NegatableArguments do
+  let(:test_resolver) do
+    Class.new(Resolvers::BaseResolver).tap do |klass|
+      klass.extend described_class
+      allow(klass).to receive(:name).and_return('Resolvers::TestResolver')
+    end
+  end
+
+  describe '#negated' do
+    it 'defines :not argument' do
+      test_resolver.negated {}
+
+      expect(test_resolver.arguments['not'].type.name).to eq "Types::TestResolverNegatedParamsType"
+    end
+
+    it 'defines any arguments passed as block' do
+      test_resolver.negated do
+        argument :foo, GraphQL::STRING_TYPE, required: false
+      end
+
+      expect(test_resolver.arguments['not'].type.arguments.keys).to match_array(['foo'])
+    end
+
+    it 'defines all arguments passed as block even if called multiple times' do
+      test_resolver.negated do
+        argument :foo, GraphQL::STRING_TYPE, required: false
+      end
+      test_resolver.negated do
+        argument :bar, GraphQL::STRING_TYPE, required: false
+      end
+
+      expect(test_resolver.arguments['not'].type.arguments.keys).to match_array(%w[foo bar])
+    end
+
+    it 'allows to specify custom argument name' do
+      test_resolver.negated(param_key: :negative) {}
+
+      expect(test_resolver.arguments).to include('negative')
+    end
+  end
+end