From 22d7834ae96a8d7973d0c406025e82e8c2d8c65a Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Mon, 8 Jun 2026 15:27:10 +0000
Subject: [PATCH] Fix exclude-only multi filters matching nothing
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MultiCriterion.to_q (used by SessionFilter for game/device) unconditionally added
field__in=value even when value was empty, and __in=[] matches no rows — so a
filter with only excludes (e.g. device excludes 11, no game/device includes)
returned zero results. Guard the empty value like ChoiceCriterion already does,
so an exclude-only criterion means 'all rows except the excluded ids'.

https://claude.ai/code/session_01XzhXvMvw42CQGc9kmin3GS
---
 common/criteria.py    |  4 +++-
 tests/test_filters.py | 24 ++++++++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/common/criteria.py b/common/criteria.py
index ba4406b..6ae3493 100644
--- a/common/criteria.py
+++ b/common/criteria.py
@@ -277,7 +277,9 @@ class MultiCriterion(_Criterion):
     def to_q(self, field_name: str) -> Q:
         m = self.modifier
         if m == Modifier.INCLUDES:
-            q = Q(**{f"{field_name}__in": self.value})
+            q = Q()
+            if self.value:
+                q &= Q(**{f"{field_name}__in": self.value})
             if self.excludes:
                 q &= ~Q(**{f"{field_name}__in": self.excludes})
             return q
diff --git a/tests/test_filters.py b/tests/test_filters.py
index f25b617..84363f3 100644
--- a/tests/test_filters.py
+++ b/tests/test_filters.py
@@ -10,6 +10,7 @@ from common.criteria import (
     ChoiceCriterion,
     IntCriterion,
     Modifier,
+    MultiCriterion,
     StringCriterion,
 )
 from common.components import FilterBar
@@ -98,6 +99,29 @@ class TestChoiceCriterion:
         assert c.to_q("status") == ~Q(status__in=["f"])
 
 
+class TestMultiCriterion:
+    def test_includes(self):
+        c = MultiCriterion(value=[797], modifier=Modifier.INCLUDES)
+        assert c.to_q("game_id") == Q(game_id__in=[797])
+
+    def test_excludes_only_empty_value(self):
+        """Exclude one device with no includes — value=[], excludes=[11].
+
+        Regression: an empty ``value`` must not add ``__in=[]`` (which matches
+        nothing); the criterion should mean "all rows except device 11".
+        """
+        c = MultiCriterion(value=[], excludes=[11], modifier=Modifier.INCLUDES)
+        assert c.to_q("device_id") == ~Q(device_id__in=[11])
+
+    def test_include_and_exclude(self):
+        c = MultiCriterion(value=[1], excludes=[2], modifier=Modifier.INCLUDES)
+        assert c.to_q("game_id") == Q(game_id__in=[1]) & ~Q(game_id__in=[2])
+
+    def test_is_null(self):
+        c = MultiCriterion(value=[], modifier=Modifier.IS_NULL)
+        assert c.to_q("device_id") == Q(device_id__isnull=True)
+
+
 class TestChoiceCriterionAgainstDB:
     """Verify ChoiceCriterion produces correct DB results."""