Fix sending new contributor notifications (#3477)

We broke sending new contributor notifications in #2677 by moving the is_new_contributor() check after the point when translation is saved, while keeping its logic (return True whether the user has not made any contributions yet). That way the function always returns False.

This changeset:
* Fixes the logic to detect that the submitted translation is the user's first contribution to the locale.
* Add an additional check that the new contributor notification is not sent to project managers.
* Adds a test case to checks whether the new contributor notification is sent and that it's only sent once.

pontoon/base/models/user.py

@@ -281,12 +281,13 @@ def can_translate(self, locale, project):
     return self.has_perm("base.can_translate_locale", locale)
 
 
-def is_new_contributor(self, locale):
-    """Return True if the user hasn't made contributions to the locale yet."""
+def has_one_contribution(self, locale):
+    """Return True if the user has made just 1 contribution to the locale."""
     return (
-        not self.translation_set.filter(locale=locale)
+        self.translation_set.filter(locale=locale)
         .exclude(entity__resource__project__system_project=True)
-        .exists()
+        .count()
+        == 1
     )
 
 
@@ -499,7 +500,7 @@ def latest_action(self):
 User.add_to_class("has_approved_translations", has_approved_translations)
 User.add_to_class("top_contributed_locale", top_contributed_locale)
 User.add_to_class("can_translate", can_translate)
-User.add_to_class("is_new_contributor", is_new_contributor)
+User.add_to_class("has_one_contribution", has_one_contribution)
 User.add_to_class("notification_list", notification_list)
 User.add_to_class("menu_notifications", menu_notifications)
 User.add_to_class("unread_notifications_display", unread_notifications_display)

pontoon/translations/tests/test_views.py

@@ -1,3 +1,5 @@
+from unittest.mock import patch
+
 import pytest
 
 from django.urls import reverse
@@ -210,6 +212,76 @@ def test_run_checks_during_translation_update(
     assert warning.message == "trailing argument 1 `s` missing"
 
 
+@patch("notifications.signals.notify.send")
+@pytest.mark.django_db
+def test_notify_managers_on_first_contribution(
+    mock_notify,
+    member,
+    entity_a,
+    entity_b,
+    locale_a,
+    user_a,
+    user_b,
+    project_locale_a,
+    request_create_translation,
+):
+    """
+    Test that managers are notified when a user makes their first contribution
+    to a locale.
+    """
+    translation = TranslationFactory(
+        entity=entity_a,
+        locale=locale_a,
+        user=user_b,  # user_b has no contributions to locale_a yet
+        approved=True,
+        active=True,
+    )
+
+    # Set user_a as a manager for locale_a and subscribe it to new contributor notifications
+    translation.locale.managers_group.user_set.add(user_a)
+    user_a.profile.new_contributor_notifications = True
+    user_a.profile.save()
+
+    mock_notify.reset_mock()
+    response = request_create_translation(
+        member.client,
+        entity=translation.entity.pk,
+        original=translation.entity.string,
+        locale=translation.locale.code,
+        translation="First translation",
+    )
+
+    assert response.status_code == 200
+    assert response.json()["status"]
+
+    mock_notify.assert_called_once()
+
+    # Check that the new contributor notification was sent to the correct manager
+    notify_args = mock_notify.call_args[1]
+    assert notify_args["recipient"] == user_a
+    assert notify_args["category"] == "new_contributor"
+
+    # Check that the new contributor notification is only sent for the first contribution
+    second_translation = TranslationFactory(
+        entity=entity_b,
+        locale=locale_a,
+        user=user_b,
+        approved=True,
+        active=True,
+    )
+
+    mock_notify.reset_mock()
+    response = request_create_translation(
+        member.client,
+        entity=second_translation.entity.pk,
+        original=second_translation.entity.string,
+        locale=second_translation.locale.code,
+        translation="Second translation",
+    )
+
+    mock_notify.assert_not_called()
+
+
 @pytest.fixture
 def approved_translation(locale_a, project_locale_a, entity_a, user_a):
     return TranslationFactory(

pontoon/translations/views.py

@@ -126,7 +126,11 @@ def create_translation(request):
         )
 
     # When user makes their first contribution to the team, notify team managers
-    first_contribution = not project.system_project and user.is_new_contributor(locale)
+    first_contribution = (
+        not project.system_project
+        and user != project.contact
+        and user.has_one_contribution(locale)
+    )
     if first_contribution:
         description = render_to_string(
             "messaging/notifications/new_contributor.html",