Fix NULL counts for empty imprints/universes on publisher page

comicsdb/views/publisher.py

@@ -2,6 +2,7 @@
 
 from django.contrib.auth.mixins import LoginRequiredMixin, PermissionRequiredMixin
 from django.db.models import Count, OuterRef, Subquery
+from django.db.models.functions import Coalesce
 from django.shortcuts import get_object_or_404
 from django.urls import reverse_lazy
 from django.views.generic import DetailView, ListView
@@ -115,13 +116,13 @@ def get_context_data(self, **kwargs):
         # Paginate imprints - only load first batch
         if imprint_count > 0:
             context["imprints"] = publisher.imprints.annotate(
-                series_count=Subquery(_imprint_series_count_sq)
+                series_count=Coalesce(Subquery(_imprint_series_count_sq), 0)
             )[:DETAIL_PAGINATE_BY]
 
         # Paginate universes - only load first batch
         if universe_count > 0:
             context["universes"] = publisher.universes.annotate(
-                issue_count=Subquery(_universe_issue_count_sq)
+                issue_count=Coalesce(Subquery(_universe_issue_count_sq), 0)
             )[:DETAIL_PAGINATE_BY]
 
         return context
@@ -172,9 +173,9 @@ class PublisherImprintsLoadMore(LazyLoadMixin):
     slug_context_name = "publisher_slug"
 
     def get_queryset(self, parent_object, offset, limit):
-        return parent_object.imprints.annotate(series_count=Subquery(_imprint_series_count_sq))[
-            offset : offset + limit
-        ]
+        return parent_object.imprints.annotate(
+            series_count=Coalesce(Subquery(_imprint_series_count_sq), 0)
+        )[offset : offset + limit]
 
 
 class PublisherUniversesLoadMore(LazyLoadMixin):
@@ -187,6 +188,6 @@ class PublisherUniversesLoadMore(LazyLoadMixin):
     slug_context_name = "publisher_slug"
 
     def get_queryset(self, parent_object, offset, limit):
-        return parent_object.universes.annotate(issue_count=Subquery(_universe_issue_count_sq))[
-            offset : offset + limit
-        ]
+        return parent_object.universes.annotate(
+            issue_count=Coalesce(Subquery(_universe_issue_count_sq), 0)
+        )[offset : offset + limit]

tests/comicsdb/test_publisher_views.py

@@ -77,6 +77,23 @@ def test_publisher_detail_with_imprint_and_universe_counts(
     assert resp.context["universes"][0].issue_count == 1
 
 
+def test_publisher_detail_with_empty_imprint_and_universe(
+    dc_comics, vertigo_imprint, earth_2_universe, auto_login_user
+):
+    """Regression test: imprints/universes with zero series/issues must render.
+
+    The correlated-subquery annotation returns NULL (not 0) when an imprint
+    has no series or a universe has no issues, which also crashed the
+    ``{% blocktrans count %}`` tag (e.g. /publisher/dc-comics/ in production
+    where an imprint/universe existed with nothing tagged to it yet).
+    """
+    client, _ = auto_login_user()
+    resp = client.get(f"/publisher/{dc_comics.slug}/")
+    assert resp.status_code == HTML_OK_CODE
+    assert resp.context["imprints"][0].series_count == 0
+    assert resp.context["universes"][0].issue_count == 0
+
+
 def test_publisher_redirect(dc_comics, auto_login_user):
     client, _ = auto_login_user()
     resp = client.get(f"/publisher/{dc_comics.pk}/")