Ensure issuable state changes only fire webhooks once

* Webhooks for close and reopen events now fired in respective services only
* Prevents generic 'update' webhooks firing too

app/services/issuable_base_service.rb

@@ -184,7 +184,8 @@ class IssuableBaseService < BaseService
     old_labels = issuable.labels.to_a
     old_mentioned_users = issuable.mentioned_users.to_a
 
-    params[:label_ids] = process_label_ids(params, existing_label_ids: issuable.label_ids)
+    label_ids = process_label_ids(params, existing_label_ids: issuable.label_ids)
+    params[:label_ids] = label_ids if labels_changing?(issuable.label_ids, label_ids)
 
     if params.present? && update_issuable(issuable, params)
       # We do not touch as it will affect a update on updated_at field
@@ -201,6 +202,10 @@ class IssuableBaseService < BaseService
     issuable
   end
 
+  def labels_changing?(old_label_ids, new_label_ids)
+    old_label_ids.sort != new_label_ids.sort
+  end
+
   def change_state(issuable)
     case params.delete(:state_event)
     when 'reopen'

changelogs/unreleased/25339-2-webhooks-fired-for-issue-closed-and-reopened.yml

@@ -0,0 +1,4 @@
+---
+title: Ensure issuable state changes only fire webhooks once
+merge_request: 
+author: 

spec/services/issues/update_service_spec.rb

@@ -376,5 +376,10 @@ describe Issues::UpdateService, services: true do
       let(:mentionable) { issue }
       include_examples 'updating mentions', Issues::UpdateService
     end
+
+    include_examples 'issuable update service' do
+      let(:open_issuable) { issue }
+      let(:closed_issuable) { create(:closed_issue, project: project) }
+    end
   end
 end

spec/services/merge_requests/update_service_spec.rb

@@ -320,5 +320,10 @@ describe MergeRequests::UpdateService, services: true do
         expect(issue_ids).to be_empty
       end
     end
+
+    include_examples 'issuable update service' do
+      let(:open_issuable) { merge_request }
+      let(:closed_issuable) { create(:closed_merge_request, source_project: project) }
+    end
   end
 end

spec/support/services/issuable_update_service_shared_examples.rb

@@ -0,0 +1,17 @@
+shared_examples 'issuable update service' do
+  context 'changing state' do
+    before { expect(project).to receive(:execute_hooks).once }
+
+    context 'to reopened' do
+      it 'executes hooks only once' do
+        described_class.new(project, user, state_event: 'reopen').execute(closed_issuable)
+      end
+    end
+
+    context 'to closed' do
+      it 'executes hooks only once' do
+        described_class.new(project, user, state_event: 'close').execute(open_issuable)
+      end
+    end
+  end
+end