fix: if JsonObject serialized to None then return null_value instea…

…d of `string_value` (#771)

* fix: if JsonObject serialized to None then return `null_value` instead of `string_value`

Co-authored-by: Astha Mohta <35952883+asthamohta@users.noreply.github.com>
Co-authored-by: Anthonios Partheniou <partheniou@google.com>
Co-authored-by: Ilya Gurov <gurovilya9@gmail.com>

google/cloud/spanner_v1/_helpers.py

@@ -165,7 +165,11 @@ def _make_value_pb(value):
         _assert_numeric_precision_and_scale(value)
         return Value(string_value=str(value))
     if isinstance(value, JsonObject):
-        return Value(string_value=value.serialize())
+        value = value.serialize()
+        if value is None:
+            return Value(null_value="NULL_VALUE")
+        else:
+            return Value(string_value=value)
 
     raise ValueError("Unknown type: %s" % (value,))
 

tests/unit/test__helpers.py

@@ -306,6 +306,13 @@ def test_w_json(self):
         self.assertIsInstance(value_pb, Value)
         self.assertEqual(value_pb.string_value, value)
 
+    def test_w_json_None(self):
+        from google.cloud.spanner_v1 import JsonObject
+
+        value = JsonObject(None)
+        value_pb = self._callFUT(value)
+        self.assertTrue(value_pb.HasField("null_value"))
+
 
 class Test_make_list_value_pb(unittest.TestCase):
     def _callFUT(self, *args, **kw):