fix: convert unspecified to serializable

Author: olavloite

google/cloud/sqlalchemy_spanner/requirements.py

@@ -102,7 +102,10 @@ def get_isolation_levels(self, _):
         Returns:
             dict: isolation levels description.
         """
-        return {"default": "SERIALIZABLE", "supported": ["SERIALIZABLE", "AUTOCOMMIT"]}
+        return {
+            "default": "SERIALIZABLE",
+            "supported": ["SERIALIZABLE", "REPEATABLE READ", "AUTOCOMMIT"],
+        }
 
     @property
     def precision_numerics_enotation_large(self):

google/cloud/sqlalchemy_spanner/sqlalchemy_spanner.py

@@ -813,6 +813,7 @@ def default_isolation_level(self):
 
     @default_isolation_level.setter
     def default_isolation_level(self, value):
+
         self._default_isolation_level = value
 
     def _check_unicode_returns(self, connection, additional_tests=None):
@@ -1700,16 +1701,18 @@ def get_isolation_level(self, conn_proxy):
             return "AUTOCOMMIT"
 
         level = conn.isolation_level
+        if level == TransactionOptions.IsolationLevel.ISOLATION_LEVEL_UNSPECIFIED:
+            level = TransactionOptions.IsolationLevel.SERIALIZABLE
         if isinstance(level, TransactionOptions.IsolationLevel):
             level = self._isolation_level_to_string(level)
 
         return level
 
     def _string_to_isolation_level(self, name):
         try:
-            return TransactionOptions.IsolationLevel[name.upper().replace(" ", "_")]
+            return TransactionOptions.IsolationLevel[name.replace(" ", "_")]
         except KeyError:
-            return TransactionOptions.IsolationLevel.ISOLATION_LEVEL_UNSPECIFIED
+            raise ValueError("Invalid isolation level name '%s'" % name)
 
     def _isolation_level_to_string(self, level):
         return level.name.replace("_", " ")

test/mockserver_tests/test_isolation_level.py

@@ -11,7 +11,7 @@
 # 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.
-
+import pytest
 from sqlalchemy import create_engine
 from sqlalchemy.orm import Session
 from sqlalchemy.testing import eq_, is_instance_of
@@ -144,6 +144,19 @@ def test_auto_commit(self):
             execute_request.transaction.begin,
         )
 
+    def test_invalid_isolation_level(self):
+        from test.mockserver_tests.isolation_level_model import Singer
+
+        engine = create_engine(
+            "spanner:///projects/p/instances/i/databases/d",
+            connect_args={"client": self.client, "pool": FixedSizePool(size=10)},
+        )
+        with pytest.raises(ValueError):
+            with Session(engine.execution_options(isolation_level="foo")) as session:
+                singer = Singer(name="Test")
+                session.add(singer)
+                session.commit()
+
     def verify_isolation_level(self, level):
         # Verify the requests that we got.
         requests = self.spanner_service.requests