Show meaningful message on /due quick action with invalid date

When using /due quick action with an invalid date a meaninful error
message is shown.

changelogs/unreleased/64009-show-a-meaningful-error-message-when-due-quick_actions-command-fail.yml

+---
+title: Show meaningful message on /due quick action with invalid date
+merge_request: 32349
+author: Jacopo Beschi @jacopo-beschi
+type: changed

lib/gitlab/quick_actions/issue_actions.rb

@@ -25,7 +25,11 @@ module Gitlab
           Chronic.parse(due_date_param).try(:to_date)
         end
         command :due do |due_date|
-          @updates[:due_date] = due_date if due_date
+          if due_date
+            @updates[:due_date] = due_date
+          else
+            @execution_message[:due] = _('Failed to set due date because the date format is invalid.')
+          end
         end
 
         desc _('Remove due date')

locale/gitlab.pot

@@ -4984,6 +4984,9 @@ msgstr ""
 msgid "Failed to save preferences."
 msgstr ""
 
+msgid "Failed to set due date because the date format is invalid."
+msgstr ""
+
 msgid "Failed to update branch!"
 msgstr ""
 

spec/services/quick_actions/interpret_service_spec.rb

@@ -970,34 +970,6 @@ describe QuickActions::InterpretService do
       let(:issuable) { merge_request }
     end
 
-    it_behaves_like 'due command' do
-      let(:content) { '/due 2016-08-28' }
-      let(:issuable) { issue }
-    end
-
-    it_behaves_like 'due command' do
-      let(:content) { '/due tomorrow' }
-      let(:issuable) { issue }
-      let(:expected_date) { Date.tomorrow }
-    end
-
-    it_behaves_like 'due command' do
-      let(:content) { '/due 5 days from now' }
-      let(:issuable) { issue }
-      let(:expected_date) { 5.days.from_now.to_date }
-    end
-
-    it_behaves_like 'due command' do
-      let(:content) { '/due in 2 days' }
-      let(:issuable) { issue }
-      let(:expected_date) { 2.days.from_now.to_date }
-    end
-
-    it_behaves_like 'empty command' do
-      let(:content) { '/due foo bar' }
-      let(:issuable) { issue }
-    end
-
     it_behaves_like 'empty command' do
       let(:content) { '/due 2016-08-28' }
       let(:issuable) { merge_request }
@@ -1131,6 +1103,39 @@ describe QuickActions::InterpretService do
       end
     end
 
+    context '/due command' do
+      it 'returns invalid date format message when the due date is invalid' do
+        issue = build(:issue, project: project)
+
+        _, _, message = service.execute('/due invalid date', issue)
+
+        expect(message).to eq('Failed to set due date because the date format is invalid.')
+      end
+
+      it_behaves_like 'due command' do
+        let(:content) { '/due 2016-08-28' }
+        let(:issuable) { issue }
+      end
+
+      it_behaves_like 'due command' do
+        let(:content) { '/due tomorrow' }
+        let(:issuable) { issue }
+        let(:expected_date) { Date.tomorrow }
+      end
+
+      it_behaves_like 'due command' do
+        let(:content) { '/due 5 days from now' }
+        let(:issuable) { issue }
+        let(:expected_date) { 5.days.from_now.to_date }
+      end
+
+      it_behaves_like 'due command' do
+        let(:content) { '/due in 2 days' }
+        let(:issuable) { issue }
+        let(:expected_date) { 2.days.from_now.to_date }
+      end
+    end
+
     context '/copy_metadata command' do
       let(:todo_label) { create(:label, project: project, title: 'To Do') }
       let(:inreview_label) { create(:label, project: project, title: 'In Review') }