fix(sessions): same-day sessions no longer crash log/invoice lookup

app/my_practice/tests/test_clinical.py

@@ -11,7 +11,7 @@
     session_duration_edit
 """
 
-from datetime import date
+from datetime import date, time
 from decimal import Decimal
 
 from django.contrib.auth.models import User
@@ -341,6 +341,72 @@ def test_post_finds_existing_session(self):
         existing.refresh_from_db()
         self.assertTrue(hasattr(existing, "log"))
 
+    def test_post_two_sessions_same_day_attaches_to_unlogged_one(self):
+        """With two sessions on one date, the log goes to the one without a log yet."""
+        logged = Session.objects.create(
+            client=self.client_obj, session_date=date(2026, 3, 20), session_time=time(9, 0)
+        )
+        SessionLog.objects.create(session=logged, content="Morning")
+        afternoon = Session.objects.create(
+            client=self.client_obj, session_date=date(2026, 3, 20), session_time=time(15, 0)
+        )
+        response = self.http.post(self._url(), {"session_date": "2026-03-20", "content": "Later"})
+        self.assertEqual(response.status_code, 302)
+        afternoon.refresh_from_db()
+        self.assertEqual(afternoon.log.content, "Later")
+        self.assertEqual(Session.objects.filter(client=self.client_obj).count(), 2)
+
+    def test_post_skips_cancelled_twin_left_by_reschedule(self):
+        """A cancelled session at the same slot (reschedule leftover) is not chosen."""
+        Session.objects.create(
+            client=self.client_obj,
+            session_date=date(2026, 3, 20),
+            session_time=time(10, 0),
+            cancelled=True,
+        )
+        live = Session.objects.create(
+            client=self.client_obj, session_date=date(2026, 3, 20), session_time=time(10, 0)
+        )
+        self.http.post(self._url(), {"session_date": "2026-03-20", "content": "Notes"})
+        live.refresh_from_db()
+        self.assertEqual(live.log.content, "Notes")
+
+    def test_post_logged_live_session_with_cancelled_twin_redirects_to_edit(self):
+        """Once the live session is logged, its unlogged cancelled twin is not used."""
+        Session.objects.create(
+            client=self.client_obj,
+            session_date=date(2026, 3, 20),
+            session_time=time(10, 0),
+            cancelled=True,
+        )
+        live = Session.objects.create(
+            client=self.client_obj, session_date=date(2026, 3, 20), session_time=time(10, 0)
+        )
+        log = SessionLog.objects.create(session=live, content="Existing")
+        response = self.http.post(self._url(), {"session_date": "2026-03-20"})
+        self.assertRedirects(
+            response,
+            reverse("session_log_edit", kwargs={"client_pk": self.client_obj.pk, "log_pk": log.pk}),
+        )
+
+    def test_post_two_logged_sessions_same_day_redirects_to_edit(self):
+        """If every session that day already has a log, redirect to editing the first."""
+        first = Session.objects.create(
+            client=self.client_obj, session_date=date(2026, 3, 20), session_time=time(9, 0)
+        )
+        second = Session.objects.create(
+            client=self.client_obj, session_date=date(2026, 3, 20), session_time=time(15, 0)
+        )
+        first_log = SessionLog.objects.create(session=first, content="A")
+        SessionLog.objects.create(session=second, content="B")
+        response = self.http.post(self._url(), {"session_date": "2026-03-20"})
+        self.assertRedirects(
+            response,
+            reverse(
+                "session_log_edit", kwargs={"client_pk": self.client_obj.pk, "log_pk": first_log.pk}
+            ),
+        )
+
     def test_post_invalid_date_redirects(self):
         """POST with an unparseable session_date redirects with error, no Session created."""
         response = self.http.post(self._url(), {"session_date": "not-a-date"})

app/my_practice/tests/test_views_invoice_billing.py

@@ -3,7 +3,7 @@
 delete, add-sessions helpers, and the monthly billing overview.
 """
 
-from datetime import date, timedelta
+from datetime import date, time, timedelta
 from decimal import Decimal
 from unittest import mock
 
@@ -200,6 +200,33 @@ def test_create_success_creates_invoice_and_session(self):
         self.assertEqual(invoice.items.count(), 1)
         self.assertTrue(Session.objects.filter(client=self.test_client).exists())
 
+    def test_create_with_two_sessions_same_day_links_unbilled_one(self):
+        """Two existing sessions on the item's date must not crash; the item links one."""
+        for hour in (9, 15):
+            Session.objects.create(
+                client=self.test_client, session_date=date.today(), session_time=time(hour, 0)
+            )
+        response = self.client_instance.post(reverse("invoice_create"), self._formset_data())
+        self.assertRedirects(response, reverse("invoice_list"))
+        item = Invoice.objects.get(client=self.test_client).items.get()
+        self.assertEqual(item.session.session_time, time(9, 0))
+        self.assertEqual(Session.objects.filter(client=self.test_client).count(), 2)
+
+    def test_create_skips_cancelled_twin_left_by_reschedule(self):
+        """A cancelled same-slot session (reschedule leftover) is not billed."""
+        Session.objects.create(
+            client=self.test_client,
+            session_date=date.today(),
+            session_time=time(10, 0),
+            cancelled=True,
+        )
+        live = Session.objects.create(
+            client=self.test_client, session_date=date.today(), session_time=time(10, 0)
+        )
+        self.client_instance.post(reverse("invoice_create"), self._formset_data())
+        item = Invoice.objects.get(client=self.test_client).items.get()
+        self.assertEqual(item.session, live)
+
     def test_create_invalid_formset_shows_errors_and_rerenders(self):
         # Missing rate on the one required item makes the formset invalid.
         data = self._formset_data(**{"items-0-rate": ""})

app/my_practice/views/clinical_views.py

@@ -84,14 +84,22 @@ def session_log_create(request, pk):
             messages.error(request, _("Invalid date."))
             return redirect("client_detail", pk=pk)
 
-        # Find or create Session for this client + date
-        session, _created = Session.objects.get_or_create(
-            client=client,
-            session_date=session_date,
-            defaults={
-                "duration": int(request.POST.get("duration", 60)),
-            },
+        # A client can have several sessions on one date (calendar import keys on
+        # date + time, and a reschedule can leave a cancelled twin behind), so attach
+        # to the first live one still without a log rather than get_or_create, which
+        # raises MultipleObjectsReturned.
+        same_day = Session.objects.filter(client=client, session_date=session_date).order_by(
+            "session_time", "pk"
         )
+        live = same_day.filter(cancelled=False)
+        pool = live if live.exists() else same_day
+        session = pool.filter(log__isnull=True).first() or pool.first()
+        if session is None:
+            session = Session.objects.create(
+                client=client,
+                session_date=session_date,
+                duration=int(request.POST.get("duration", 60)),
+            )
 
         # Prevent duplicate logs
         if hasattr(session, "log"):

app/my_practice/views/crud_mixins.py

@@ -128,12 +128,23 @@ def attach_sessions_to_formset(formset, client) -> None:
             if not session_date:
                 item_form.instance.session = None
                 continue
-            duration = item_form.cleaned_data.get("duration") or 60
-            session, _created = Session.objects.get_or_create(
-                client=client,
-                session_date=session_date,
-                defaults={"duration": duration},
+            current = item_form.instance.session
+            if current and current.client_id == client.pk and current.session_date == session_date:
+                continue
+            # Several sessions can share a date (calendar import keys on date + time,
+            # and a reschedule can leave a cancelled twin behind): prefer a live one not
+            # yet billed instead of get_or_create, which raises MultipleObjectsReturned.
+            same_day = Session.objects.filter(client=client, session_date=session_date).order_by(
+                "session_time", "pk"
             )
+            live = same_day.filter(cancelled=False)
+            pool = live if live.exists() else same_day
+            session = pool.filter(invoice_items__isnull=True).first() or pool.first()
+            if session is None:
+                duration = item_form.cleaned_data.get("duration") or 60
+                session = Session.objects.create(
+                    client=client, session_date=session_date, duration=duration
+                )
             item_form.instance.session = session