amend valid_path_key_name() to reject only dollar signs and periods

Author: timgraham

django_mongodb_backend/fields/json.py

@@ -18,7 +18,13 @@
 )
 
 from django_mongodb_backend.lookups import builtin_lookup_expr, builtin_lookup_path
-from django_mongodb_backend.query_utils import process_lhs, process_rhs, valid_path_key_name
+from django_mongodb_backend.query_utils import process_lhs, process_rhs
+
+
+def valid_path_key_name(key_name):
+    # A value can use path syntax (field.subfield.) unless it contains a
+    # dollar sign or period.
+    return not any(char in key_name for char in ("$", "."))
 
 
 def build_json_mql_path(lhs, key_transforms, as_expr=False):

django_mongodb_backend/query_utils.py

@@ -1,5 +1,3 @@
-import re
-
 from django.core.exceptions import FullResultSet
 from django.db.models.aggregates import Aggregate
 from django.db.models.expressions import CombinedExpression, Func, Value
@@ -82,7 +80,3 @@ def is_constant_value(value):
         # Allow Func with can_use_path as a temporary exception.
         (isinstance(value, Func) and value.can_use_path)
     )
-
-
-def valid_path_key_name(key_name):
-    return bool(re.fullmatch(r"[A-Za-z0-9_]+", key_name))