From 05d095ba45cc64b65526e433b993ec2d56200cb3 Mon Sep 17 00:00:00 2001
From: Andrew Chen <48723787+chuenchen309@users.noreply.github.com>
Date: Thu, 16 Jul 2026 01:40:38 +0800
Subject: [PATCH] fix(condition): assert_in/assert_not_in wrongly reject falsy
 values present in the list

_assert_in and _assert_not_in short-circuit on `if not value`, but this
checks the truthiness of the value being tested for membership, not
whether it's absent. A falsy value that is legitimately present in the
expected list (e.g. an empty string in a picklist that allows an empty
option) is silently rejected by "in" and silently accepted by
"not in" before the actual membership check ever runs.

Every other comparator in this file (_assert_equal, _assert_greater_than,
etc.) guards with `if value is None`, not `if not value` -- these two
are the only outliers.

Fix: match the file's own established pattern, guard on `value is None`
instead.

Verified: new test (test_process_conditions_in_matches_falsy_value_present_in_list)
red before fix, green after; full test_condition_processor.py suite (5
tests) plus tests/nodes/if_else/ (24 tests) pass; full test suite (604
tests) passes; ruff + ty clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 src/graphon/utils/condition/processor.py |  4 +--
 tests/utils/test_condition_processor.py  | 32 ++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/src/graphon/utils/condition/processor.py b/src/graphon/utils/condition/processor.py
index 62128cf2..ded71d83 100644
--- a/src/graphon/utils/condition/processor.py
+++ b/src/graphon/utils/condition/processor.py
@@ -499,7 +499,7 @@ def _assert_not_null(*, value: Any) -> bool:
 
 
 def _assert_in(*, value: Any, expected: Any) -> bool:
-    if not value:
+    if value is None:
         return False
 
     match expected:
@@ -512,7 +512,7 @@ def _assert_in(*, value: Any, expected: Any) -> bool:
 
 
 def _assert_not_in(*, value: Any, expected: Any) -> bool:
-    if not value:
+    if value is None:
         return True
 
     match expected:
diff --git a/tests/utils/test_condition_processor.py b/tests/utils/test_condition_processor.py
index 5e7a513f..34266e6e 100644
--- a/tests/utils/test_condition_processor.py
+++ b/tests/utils/test_condition_processor.py
@@ -125,6 +125,38 @@ def test_process_conditions_contains_supports_string_and_list_values() -> None:
     assert list_result.final_result is True
 
 
+def test_process_conditions_in_matches_falsy_value_present_in_list() -> None:
+    condition_processor = ConditionProcessor()
+    variable_pool = VariablePool()
+    variable_pool.add(["test_node_id", "choice"], "")
+
+    in_result = condition_processor.process_conditions(
+        variable_pool=variable_pool,
+        conditions=[
+            Condition(
+                variable_selector=["test_node_id", "choice"],
+                comparison_operator="in",
+                value=["", "a", "b"],
+            ),
+        ],
+        operator="and",
+    )
+    not_in_result = condition_processor.process_conditions(
+        variable_pool=variable_pool,
+        conditions=[
+            Condition(
+                variable_selector=["test_node_id", "choice"],
+                comparison_operator="not in",
+                value=["", "a", "b"],
+            ),
+        ],
+        operator="and",
+    )
+
+    assert in_result.final_result is True
+    assert not_in_result.final_result is False
+
+
 def test_process_conditions_resolves_templates_from_read_only_variable_pool() -> None:
     condition_processor = ConditionProcessor()
     variable_pool = VariablePool()