Automatically resolve alert when associated issue closes

app/models/issue.rb

@@ -139,6 +139,10 @@ class Issue < ApplicationRecord
       issue.closed_at = nil
       issue.closed_by = nil
     end
+
+    after_transition any => :closed do |issue|
+      issue.resolve_associated_alert_management_alert
+    end
   end
 
   # Alias to state machine .with_state_id method
@@ -352,6 +356,18 @@ class Issue < ApplicationRecord
     @design_collection ||= ::DesignManagement::DesignCollection.new(self)
   end
 
+  def resolve_associated_alert_management_alert
+    return unless alert_management_alert
+    return if alert_management_alert.resolve
+
+    Gitlab::AppLogger.warn(
+      message: 'Cannot resolve an associated Alert Management alert',
+      issue_id: id,
+      alert_id: alert_management_alert.id,
+      alert_errors: alert_management_alert.errors.messages
+    )
+  end
+
   private
 
   def ensure_metrics

changelogs/unreleased/216142-resolve-alert-when-associated-issue-closes.yml

+---
+title: Automatically resolve alert when associated issue closes
+merge_request: 33278
+author:
+type: added

doc/user/project/operations/alert_management.md

@@ -89,3 +89,6 @@ The Alert Management detail view enables you to create an issue with a
 description automatically populated from an alert. To create the issue,
 click the **Create Issue** button. You can then view the issue from the
 alert by clicking the **View Issue** button.
+
+Closing a GitLab issue associated with an alert changes the alert's status to Resolved.
+See [Alert Management statuses](#alert-management-statuses) for more details about statuses.

spec/models/issue_spec.rb

@@ -186,6 +186,35 @@ describe Issue do
 
       expect { issue.close }.to change { issue.state_id }.from(open_state).to(closed_state)
     end
+
+    context 'when there is an associated Alert Management Alert' do
+      context 'when alert can be resolved' do
+        let!(:alert) { create(:alert_management_alert, project: issue.project, issue: issue) }
+
+        it 'resolves an alert' do
+          expect { issue.close }.to change { alert.reload.resolved? }.to(true)
+        end
+      end
+
+      context 'when alert cannot be resolved' do
+        let!(:alert) { create(:alert_management_alert, :with_validation_errors, project: issue.project, issue: issue) }
+
+        before do
+          allow(Gitlab::AppLogger).to receive(:warn).and_call_original
+        end
+
+        it 'writes a warning into the log' do
+          issue.close
+
+          expect(Gitlab::AppLogger).to have_received(:warn).with(
+            message: 'Cannot resolve an associated Alert Management alert',
+            issue_id: issue.id,
+            alert_id: alert.id,
+            alert_errors: { hosts: ['hosts array is over 255 chars'] }
+          )
+        end
+      end
+    end
   end
 
   describe '#reopen' do