Add issuableUpdate subscription to GraphQL

New subscription is only triggered when a
work item is updated for now

app/graphql/graphql_triggers.rb

@@ -8,4 +8,8 @@ module GraphqlTriggers
   def self.issue_crm_contacts_updated(issue)
     GitlabSchema.subscriptions.trigger('issueCrmContactsUpdated', { issuable_id: issue.to_gid }, issue)
   end
+
+  def self.issuable_title_updated(issuable)
+    GitlabSchema.subscriptions.trigger('issuableTitleUpdated', { issuable_id: issuable.to_gid }, issuable)
+  end
 end

app/graphql/types/issuable_type.rb

@@ -5,10 +5,12 @@ module Types
     graphql_name 'Issuable'
     description 'Represents an issuable.'
 
-    possible_types Types::IssueType, Types::MergeRequestType
+    possible_types Types::IssueType, Types::MergeRequestType, Types::WorkItemType
 
     def self.resolve_type(object, context)
       case object
+      when WorkItem
+        Types::WorkItemType
       when Issue
         Types::IssueType
       when MergeRequest

app/graphql/types/subscription_type.rb

@@ -9,5 +9,8 @@ module Types
 
     field :issue_crm_contacts_updated, subscription: Subscriptions::IssuableUpdated, null: true,
           description: 'Triggered when the crm contacts of an issuable are updated.'
+
+    field :issuable_title_updated, subscription: Subscriptions::IssuableUpdated, null: true,
+          description: 'Triggered when the title of an issuable is updated.'
   end
 end

app/services/work_items/update_service.rb

@@ -2,5 +2,12 @@
 
 module WorkItems
   class UpdateService < ::Issues::UpdateService
+    private
+
+    def after_update(issuable)
+      super
+
+      GraphqlTriggers.issuable_title_updated(issuable) if issuable.previous_changes.key?(:title)
+    end
   end
 end

doc/api/graphql/reference/index.md

@@ -18761,6 +18761,7 @@ One of:
 - [`Epic`](#epic)
 - [`Issue`](#issue)
 - [`MergeRequest`](#mergerequest)
+- [`WorkItem`](#workitem)
 
 #### `JobNeedUnion`
 

spec/graphql/graphql_triggers_spec.rb

@@ -17,4 +17,18 @@ RSpec.describe GraphqlTriggers do
       GraphqlTriggers.issuable_assignees_updated(issue)
     end
   end
+
+  describe '.issuable_title_updated' do
+    it 'triggers the issuableTitleUpdated subscription' do
+      work_item = create(:work_item)
+
+      expect(GitlabSchema.subscriptions).to receive(:trigger).with(
+        'issuableTitleUpdated',
+        { issuable_id: work_item.to_gid },
+        work_item
+      ).and_call_original
+
+      GraphqlTriggers.issuable_title_updated(work_item)
+    end
+  end
 end

spec/graphql/types/issuable_type_spec.rb

@@ -4,7 +4,7 @@ require 'spec_helper'
 
 RSpec.describe GitlabSchema.types['Issuable'] do
   it 'returns possible types' do
-    expect(described_class.possible_types).to include(Types::IssueType, Types::MergeRequestType)
+    expect(described_class.possible_types).to include(Types::IssueType, Types::MergeRequestType, Types::WorkItemType)
   end
 
   describe '.resolve_type' do
@@ -16,6 +16,10 @@ RSpec.describe GitlabSchema.types['Issuable'] do
       expect(described_class.resolve_type(build(:merge_request), {})).to eq(Types::MergeRequestType)
     end
 
+    it 'resolves work items' do
+      expect(described_class.resolve_type(build(:work_item), {})).to eq(Types::WorkItemType)
+    end
+
     it 'raises an error for invalid types' do
       expect { described_class.resolve_type(build(:user), {}) }.to raise_error 'Unsupported issuable type'
     end

spec/graphql/types/subscription_type_spec.rb

@@ -7,6 +7,7 @@ RSpec.describe GitlabSchema.types['Subscription'] do
     expected_fields = %i[
       issuable_assignees_updated
       issue_crm_contacts_updated
+      issuable_title_updated
     ]
 
     expect(described_class).to have_graphql_fields(*expected_fields).only

spec/services/work_items/update_service_spec.rb

@@ -18,6 +18,26 @@ RSpec.describe WorkItems::UpdateService do
       stub_spam_services
     end
 
+    context 'when title is changed' do
+      let(:opts) { { title: 'changed' } }
+
+      it 'triggers issuable_title_updated graphql subscription' do
+        expect(GraphqlTriggers).to receive(:issuable_title_updated).with(work_item).and_call_original
+
+        update_work_item
+      end
+    end
+
+    context 'when title is not changed' do
+      let(:opts) { { description: 'changed' } }
+
+      it 'does not trigger issuable_title_updated graphql subscription' do
+        expect(GraphqlTriggers).not_to receive(:issuable_title_updated)
+
+        update_work_item
+      end
+    end
+
     context 'when updating state_event' do
       context 'when state_event is close' do
         let(:opts) { { state_event: 'close' } }