fix: don't update Slack messages if resolution note text not changed (#5126)

# What this PR does

Reduces the number of `chat.update` Slack API calls when a resolution
note is updated with the same text.

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## Checklist

- [x] Unit, integration, and e2e (if applicable) tests updated
- [x] Documentation added (or `pr:no public docs` PR label added if not
required)
- [x] Added the relevant release notes label (see labels prefixed w/
`release:`). These labels dictate how your PR will
    show up in the autogenerated release notes.

engine/apps/public_api/tests/test_resolution_notes.py

@@ -106,8 +106,14 @@ def test_get_resolution_note(
     assert response.data == result
 
 
+@patch("apps.alerts.tasks.send_update_resolution_note_signal.send_update_resolution_note_signal.apply_async")
 @pytest.mark.django_db
-def test_create_resolution_note(make_organization_and_user_with_token, make_alert_receive_channel, make_alert_group):
+def test_create_resolution_note(
+    mock_send_update_resolution_note_signal,
+    make_organization_and_user_with_token,
+    make_alert_receive_channel,
+    make_alert_group,
+):
     organization, user, token = make_organization_and_user_with_token()
     client = APIClient()
 
@@ -137,6 +143,8 @@ def test_create_resolution_note(make_organization_and_user_with_token, make_aler
     assert response.status_code == status.HTTP_201_CREATED
     assert response.data == result
 
+    mock_send_update_resolution_note_signal.assert_called_once()
+
 
 @pytest.mark.django_db
 def test_create_resolution_note_invalid_text(
@@ -163,8 +171,10 @@ def test_create_resolution_note_invalid_text(
     assert response.data["text"][0] == "This field may not be blank."
 
 
+@patch("apps.alerts.tasks.send_update_resolution_note_signal.send_update_resolution_note_signal.apply_async")
 @pytest.mark.django_db
 def test_update_resolution_note(
+    mock_send_update_resolution_note_signal,
     make_organization_and_user_with_token,
     make_alert_receive_channel,
     make_alert_group,
@@ -206,6 +216,39 @@ def test_update_resolution_note(
     assert resolution_note.text == result["text"]
     assert response.data == result
 
+    mock_send_update_resolution_note_signal.assert_called_once()
+
+
+@patch("apps.alerts.tasks.send_update_resolution_note_signal.send_update_resolution_note_signal.apply_async")
+@pytest.mark.django_db
+def test_update_resolution_note_same_text(
+    mock_send_update_resolution_note_signal,
+    make_organization_and_user_with_token,
+    make_alert_receive_channel,
+    make_alert_group,
+    make_resolution_note,
+):
+    organization, user, token = make_organization_and_user_with_token()
+    client = APIClient()
+
+    alert_receive_channel = make_alert_receive_channel(organization)
+    alert_group = make_alert_group(alert_receive_channel)
+
+    resolution_note = make_resolution_note(
+        alert_group=alert_group,
+        source=ResolutionNote.Source.WEB,
+        author=user,
+    )
+
+    url = reverse("api-public:resolution_notes-detail", kwargs={"pk": resolution_note.public_primary_key})
+    response = client.put(
+        url, data={"text": resolution_note.message_text}, format="json", HTTP_AUTHORIZATION=f"{token}"
+    )
+    assert response.status_code == status.HTTP_200_OK
+
+    # update signal shouldn't be sent when text doesn't change
+    mock_send_update_resolution_note_signal.assert_not_called()
+
 
 @pytest.mark.django_db
 def test_update_resolution_note_invalid_source(
@@ -242,8 +285,10 @@ def test_update_resolution_note_invalid_source(
     assert response.data["detail"] == "Cannot update message with this source type"
 
 
+@patch("apps.alerts.tasks.send_update_resolution_note_signal.send_update_resolution_note_signal.apply_async")
 @pytest.mark.django_db
 def test_delete_resolution_note(
+    mock_send_update_resolution_note_signal,
     make_organization_and_user_with_token,
     make_alert_receive_channel,
     make_alert_group,
@@ -272,6 +317,7 @@ def test_delete_resolution_note(
     resolution_note.refresh_from_db()
 
     assert resolution_note.deleted_at is not None
+    mock_send_update_resolution_note_signal.assert_called_once()
 
     response = client.get(url, format="json", HTTP_AUTHORIZATION=f"{token}")
 

engine/apps/public_api/views/resolution_notes.py

@@ -56,20 +56,16 @@ class ResolutionNoteView(RateLimitHeadersMixin, UpdateSerializerMixin, ModelView
         except ResolutionNote.DoesNotExist:
             raise NotFound
 
-    def dispatch(self, request, *args, **kwargs):
-        result = super().dispatch(request, *args, **kwargs)
+    def perform_create(self, serializer):
+        super().perform_create(serializer)
+        send_update_resolution_note_signal.apply_async((serializer.instance.alert_group.pk, serializer.instance.pk))
 
-        # send signal to update alert group and resolution_note
-        method = request.method.lower()
-        if method in ["post", "put", "patch", "delete"]:
-            instance_id = self.kwargs.get("pk") or result.data.get("id")
-            if instance_id:
-                instance = ResolutionNote.objects_with_deleted.filter(public_primary_key=instance_id).first()
-                if instance is not None:
-                    send_update_resolution_note_signal.apply_async(
-                        kwargs={
-                            "alert_group_pk": instance.alert_group.pk,
-                            "resolution_note_pk": instance.pk,
-                        }
-                    )
-        return result
+    def perform_update(self, serializer):
+        is_text_updated = serializer.instance.message_text != serializer.validated_data["message_text"]
+        super().perform_update(serializer)
+        if is_text_updated:
+            send_update_resolution_note_signal.apply_async((serializer.instance.alert_group.pk, serializer.instance.pk))
+
+    def perform_destroy(self, instance):
+        super().perform_destroy(instance)
+        send_update_resolution_note_signal.apply_async((instance.alert_group.pk, instance.pk))