fix: implement $not filter support in ChromaDB vector store (#5485)

tests/vector_stores/test_chroma.py

@@ -252,6 +252,48 @@ def test_generate_where_clause_non_string_values():
     assert result == expected
 
 
+def test_generate_where_clause_not_single_equality():
+    """Test $not with a single equality condition."""
+    filters = {"$not": [{"status": "archived"}]}
+    result = ChromaDB._generate_where_clause(filters)
+    assert result == {"status": {"$ne": "archived"}}
+
+
+def test_generate_where_clause_not_multiple_conditions():
+    """Test $not with multiple conditions (OR semantics, negated to AND)."""
+    filters = {"$not": [{"status": "archived"}, {"type": "draft"}]}
+    result = ChromaDB._generate_where_clause(filters)
+    assert result == {"$and": [{"status": {"$ne": "archived"}}, {"type": {"$ne": "draft"}}]}
+
+
+def test_generate_where_clause_not_with_operators():
+    """Test $not negates comparison operators correctly."""
+    filters = {"$not": [{"count": {"gt": 5}}]}
+    result = ChromaDB._generate_where_clause(filters)
+    assert result == {"count": {"$lte": 5}}
+
+
+def test_generate_where_clause_not_in_to_nin():
+    """Test $not converts 'in' to $nin."""
+    filters = {"$not": [{"status": {"in": ["archived", "deleted"]}}]}
+    result = ChromaDB._generate_where_clause(filters)
+    assert result == {"status": {"$nin": ["archived", "deleted"]}}
+
+
+def test_generate_where_clause_not_multi_field_condition():
+    """Test $not with multi-field condition uses De Morgan's (AND -> OR)."""
+    filters = {"$not": [{"status": "archived", "type": "draft"}]}
+    result = ChromaDB._generate_where_clause(filters)
+    assert result == {"$or": [{"status": {"$ne": "archived"}}, {"type": {"$ne": "draft"}}]}
+
+
+def test_generate_where_clause_not_combined_with_other_filters():
+    """Test $not combined with regular filters."""
+    filters = {"user_id": "alice", "$not": [{"status": "archived"}]}
+    result = ChromaDB._generate_where_clause(filters)
+    assert result == {"$and": [{"user_id": {"$eq": "alice"}}, {"status": {"$ne": "archived"}}]}
+
+
 def test_chroma_config_accepts_default_tmp_path():
     """Test that ChromaDbConfig accepts the default /tmp/chroma path."""
     config = ChromaDbConfig(path="/tmp/chroma")