Firestore: __add__ function for FieldPaths

firestore/google/cloud/firestore_v1beta1/_helpers.py

@@ -178,6 +178,22 @@ def __eq__(self, other):
             return self.parts == other.parts
         return NotImplemented
 
+    def __add__(self, other):
+        """Adds `other` field path to end of this field path.
+
+        Args:
+            other (~google.cloud.firestore_v1beta1._helpers.FieldPath, str):
+                The field path to add to the end of this `FieldPath`.
+        """
+        if isinstance(other, FieldPath):
+            parts = self.parts + other.parts
+            return FieldPath(*parts)
+        elif isinstance(other, six.string_types):
+            parts = self.parts + FieldPath.from_string(other).parts
+            return FieldPath(*parts)
+        else:
+            return NotImplemented
+
 
 class FieldPathHelper(object):
     """Helper to convert field names and paths for usage in a request.

firestore/tests/unit/test__helpers.py

@@ -265,6 +265,23 @@ def test_key(self):
             else:
                 self.assertEqual(key, field_path)
 
+    def test___add__(self):
+        path1 = 'a123', 'b456'
+        path2 = 'c789', 'd012'
+        path3 = 'c789.d012'
+        field_path1 = self._make_one(*path1)
+        field_path1_string = self._make_one(*path1)
+        field_path2 = self._make_one(*path2)
+        field_path1 += field_path2
+        field_path1_string += path3
+        field_path2 = field_path2 + self._make_one(*path1)
+        self.assertEqual(field_path1, self._make_one(*(path1 + path2)))
+        self.assertEqual(field_path2, self._make_one(*(path2 + path1)))
+        self.assertEqual(field_path1_string, field_path1)
+        self.assertNotEqual(field_path1, field_path2)
+        with self.assertRaises(TypeError):
+            field_path1 + 305
+
 
 class TestFieldPathHelper(unittest.TestCase):