Properly return boolean attributes in integrations API

app/models/integration.rb

@@ -165,9 +165,13 @@ class Integration < ApplicationRecord
 
     args.each do |arg|
       class_eval <<~RUBY, __FILE__, __LINE__ + 1
+        def #{arg}
+          Gitlab::Utils.to_boolean(properties['#{arg}'])
+        end
+
         def #{arg}?
           # '!!' is used because nil or empty string is converted to nil
-          !!ActiveRecord::Type::Boolean.new.cast(#{arg})
+          !!#{arg}
         end
       RUBY
     end

lib/api/entities/project_service.rb

@@ -6,10 +6,18 @@ module API
       # Expose serialized properties
       expose :properties do |service, options|
         # TODO: Simplify as part of https://gitlab.com/gitlab-org/gitlab/issues/29404
-        if service.data_fields_present?
-          service.data_fields.as_json.slice(*service.api_field_names)
-        else
-          service.properties.slice(*service.api_field_names)
+
+        attributes =
+          if service.data_fields_present?
+            service.data_fields.as_json.keys
+          else
+            service.properties.keys
+          end
+
+        attributes &= service.api_field_names
+
+        attributes.each_with_object({}) do |attribute, hash|
+          hash[attribute] = service.public_send(attribute) # rubocop:disable GitlabSecurity/PublicSend
         end
       end
     end

spec/requests/api/services_spec.rb

@@ -338,4 +338,26 @@ RSpec.describe API::Services do
       expect(response).to have_gitlab_http_status(:ok)
     end
   end
+
+  describe 'Pipelines Email Integration' do
+    let(:service_name) { 'pipelines-email' }
+
+    context 'notify_only_broken_pipelines property was saved as a string' do
+      before do
+        project.create_pipelines_email_integration(
+          active: false,
+          properties: {
+            "notify_only_broken_pipelines": "true",
+            "branches_to_be_notified": "default"
+          }
+        )
+      end
+
+      it 'returns boolean values for notify_only_broken_pipelines' do
+        get api("/projects/#{project.id}/services/#{service_name}", user)
+
+        expect(json_response['properties']['notify_only_broken_pipelines']).to eq(true)
+      end
+    end
+  end
 end