fix(sqlalchemy-spanner): register TOKENLIST in _type_map for reflection (#17911)

Table reflection raises KeyError: 'TOKENLIST' whenever a table
containing a TOKENLIST column is reflected.

Fixes this issue by registering "TOKENLIST": types.String in _type_map
in google/cloud/sqlalchemy_spanner/sqlalchemy_spanner.py.

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Fixes #<issue_number_goes_here> 🦕

Author: sakthivelmanii

packages/sqlalchemy-spanner/google/cloud/sqlalchemy_spanner/sqlalchemy_spanner.py

@@ -120,6 +120,7 @@ def process(value):
     "TIMESTAMP": types.TIMESTAMP,
     "ARRAY": types.ARRAY,
     "JSON": types.JSON,
+    "TOKENLIST": types.String,
 }
 
 

packages/sqlalchemy-spanner/tests/mockserver_tests/test_tokenlist.py

@@ -0,0 +1,26 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from sqlalchemy import types
+from sqlalchemy.testing import eq_, fixtures
+from google.cloud.sqlalchemy_spanner.sqlalchemy_spanner import _type_map, SpannerDialect
+
+
+class TokenlistTest(fixtures.TestBase):
+    def test_tokenlist_reflection_type_mapping(self):
+        """Test mockserver reflection mapping for TOKENLIST columns."""
+        dialect = SpannerDialect()
+        eq_(_type_map.get("TOKENLIST"), types.String)
+        col_type = dialect._designate_type("TOKENLIST")
+        eq_(col_type, types.String)