error on duplicated lot name

lot/migrations/0008_lot_unique_institution_and_name.py

@@ -0,0 +1,22 @@
+# Generated by Django 5.0.6 on 2025-02-21 20:58
+
+from django.conf import settings
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("lot", "0007_lottag_inbox"),
+        ("user", "0002_institution_algorithm"),
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+    ]
+
+    operations = [
+        migrations.AddConstraint(
+            model_name="lot",
+            constraint=models.UniqueConstraint(
+                fields=("owner", "name"), name="unique_institution_and_name"
+            ),
+        ),
+    ]

lot/views.py

@@ -39,9 +39,16 @@ class NewLotView(DashboardView, CreateView):
         return form
 
     def form_valid(self, form):
-        form.instance.owner = self.request.user.institution
-        form.instance.user = self.request.user
-        response = super().form_valid(form)
+        try:
+            form.instance.owner = self.request.user.institution
+            form.instance.user = self.request.user
+            response = super().form_valid(form)
+            return response
+
+        except IntegrityError:
+            messages.error(self.request, _("Lot name is already defined."))
+            return self.form_invalid(form)
+
         return response