Add connection redaction and connection extension methods

The connection redaction is in preparation for the coming authorization
changes, and the connection methods are important so that we can test
connections as if they are enumerable containers of their items.

lib/gitlab/graphql/connection_collection_methods.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Graphql
+    module ConnectionCollectionMethods
+      extend ActiveSupport::Concern
+
+      included do
+        delegate :to_a, :size, :include?, :empty?, to: :nodes
+      end
+    end
+  end
+end

lib/gitlab/graphql/connection_redaction.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Graphql
+    module ConnectionRedaction
+      class RedactionState
+        attr_reader :redactor
+        attr_reader :redacted_nodes
+
+        def redactor=(redactor)
+          @redactor = redactor
+          @redacted_nodes = nil
+        end
+
+        def redacted(&block)
+          @redacted_nodes ||= redactor.present? ? redactor.redact(yield) : yield
+        end
+      end
+
+      delegate :redactor=, to: :redaction_state
+
+      def nodes
+        redaction_state.redacted { super.to_a }
+      end
+
+      private
+
+      def redaction_state
+        @redaction_state ||= RedactionState.new
+      end
+    end
+  end
+end

lib/gitlab/graphql/pagination/array_connection.rb

+# frozen_string_literal: true
+
+# We use the Keyset / Stable cursor connection by default for ActiveRecord::Relation.
+# However, there are times when that may not be powerful enough (yet), and we
+# want to use standard offset pagination.
+module Gitlab
+  module Graphql
+    module Pagination
+      class ArrayConnection < ::GraphQL::Pagination::ArrayConnection
+        prepend ::Gitlab::Graphql::ConnectionRedaction
+        include ::Gitlab::Graphql::ConnectionCollectionMethods
+      end
+    end
+  end
+end

lib/gitlab/graphql/pagination/connections.rb

@@ -12,6 +12,10 @@ module Gitlab
           schema.connections.add(
             Gitlab::Graphql::ExternallyPaginatedArray,
             Gitlab::Graphql::Pagination::ExternallyPaginatedArrayConnection)
+
+          schema.connections.add(
+            Array,
+            Gitlab::Graphql::Pagination::ArrayConnection)
         end
       end
     end

lib/gitlab/graphql/pagination/externally_paginated_array_connection.rb

@@ -5,6 +5,9 @@ module Gitlab
   module Graphql
     module Pagination
       class ExternallyPaginatedArrayConnection < GraphQL::Pagination::ArrayConnection
+        include ::Gitlab::Graphql::ConnectionCollectionMethods
+        prepend ::Gitlab::Graphql::ConnectionRedaction
+
         def start_cursor
           items.previous_cursor
         end

lib/gitlab/graphql/pagination/keyset/connection.rb

@@ -31,6 +31,8 @@ module Gitlab
       module Keyset
         class Connection < GraphQL::Pagination::ActiveRecordRelationConnection
           include Gitlab::Utils::StrongMemoize
+          include ::Gitlab::Graphql::ConnectionCollectionMethods
+          prepend ::Gitlab::Graphql::ConnectionRedaction
 
           # rubocop: disable Naming/PredicateName
           # https://relay.dev/graphql/connections.htm#sec-undefined.PageInfo.Fields

lib/gitlab/graphql/pagination/offset_active_record_relation_connection.rb

@@ -7,6 +7,8 @@ module Gitlab
   module Graphql
     module Pagination
       class OffsetActiveRecordRelationConnection < GraphQL::Pagination::ActiveRecordRelationConnection
+        prepend ::Gitlab::Graphql::ConnectionRedaction
+        include ::Gitlab::Graphql::ConnectionCollectionMethods
       end
     end
   end

spec/lib/gitlab/graphql/pagination/array_connection_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe ::Gitlab::Graphql::Pagination::ArrayConnection do
+  let(:nodes) { (1..10) }
+
+  subject(:connection) { described_class.new(nodes, max_page_size: 100) }
+
+  it_behaves_like 'a connection with collection methods'
+
+  it_behaves_like 'a redactable connection' do
+    let(:unwanted) { 5 }
+  end
+end

spec/lib/gitlab/graphql/pagination/externally_paginated_array_connection_spec.rb

@@ -13,6 +13,12 @@ RSpec.describe Gitlab::Graphql::Pagination::ExternallyPaginatedArrayConnection d
     described_class.new(all_nodes, { max_page_size: values.size }.merge(arguments))
   end
 
+  it_behaves_like 'a connection with collection methods'
+
+  it_behaves_like 'a redactable connection' do
+    let(:unwanted) { 3 }
+  end
+
   describe '#nodes' do
     let(:paged_nodes) { connection.nodes }
 

spec/lib/gitlab/graphql/pagination/keyset/connection_spec.rb

@@ -21,6 +21,13 @@ RSpec.describe Gitlab::Graphql::Pagination::Keyset::Connection do
     Gitlab::Json.parse(Base64Bp.urlsafe_decode64(cursor))
   end
 
+  it_behaves_like 'a connection with collection methods'
+
+  it_behaves_like 'a redactable connection' do
+    let_it_be(:projects) { create_list(:project, 2) }
+    let(:unwanted) { projects.second }
+  end
+
   describe '#cursor_for' do
     let(:project) { create(:project) }
     let(:cursor)  { connection.cursor_for(project) }

spec/lib/gitlab/graphql/pagination/offset_active_record_relation_connection_spec.rb

@@ -6,4 +6,15 @@ RSpec.describe Gitlab::Graphql::Pagination::OffsetActiveRecordRelationConnection
   it 'subclasses from GraphQL::Relay::RelationConnection' do
     expect(described_class.superclass).to eq GraphQL::Pagination::ActiveRecordRelationConnection
   end
+
+  it_behaves_like 'a connection with collection methods' do
+    let(:connection) { described_class.new(Project.all) }
+  end
+
+  it_behaves_like 'a redactable connection' do
+    let_it_be(:users) { create_list(:user, 2) }
+
+    let(:connection) { described_class.new(User.all, max_page_size: 10) }
+    let(:unwanted) { users.second }
+  end
 end

spec/support/shared_examples/graphql/connection_redaction_shared_examples.rb

+# frozen_string_literal: true
+
+# requires:
+#  - `connection` (no-empty, containing `unwanted` and at least one more item)
+#  - `unwanted` (single item in collection)
+RSpec.shared_examples 'a redactable connection' do
+  context 'no redactor set' do
+    it 'contains the unwanted item' do
+      expect(connection.nodes).to include(unwanted)
+    end
+
+    it 'does not redact more than once' do
+      connection.nodes
+      r_state = connection.send(:redaction_state)
+
+      expect(r_state.redacted { raise 'Should not be called!' }).to be_present
+    end
+  end
+
+  let_it_be(:constant_redactor) do
+    Class.new do
+      def initialize(remove)
+        @remove = remove
+      end
+
+      def redact(items)
+        items - @remove
+      end
+    end
+  end
+
+  context 'redactor is set' do
+    let(:redactor) do
+      constant_redactor.new([unwanted])
+    end
+
+    before do
+      connection.redactor = redactor
+    end
+
+    it 'does not contain the unwanted item' do
+      expect(connection.nodes).not_to include(unwanted)
+      expect(connection.nodes).not_to be_empty
+    end
+
+    it 'does not redact more than once' do
+      expect(redactor).to receive(:redact).once.and_call_original
+
+      connection.nodes
+      connection.nodes
+      connection.nodes
+    end
+  end
+end

spec/support/shared_examples/graphql/connection_shared_examples.rb

+# frozen_string_literal: true
+
+RSpec.shared_examples 'a connection with collection methods' do
+  %i[to_a size include? empty?].each do |method_name|
+    it "responds to #{method_name}" do
+      expect(connection).to respond_to(method_name)
+    end
+  end
+end