Add tests and fix various bugs in ModelOutput (#7073)

* Add tests and fix various bugs in ModelOutput

* Update tests/test_model_output.py
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>

src/transformers/file_utils.py

@@ -988,6 +988,8 @@ class ModelOutput(OrderedDict):
                     setattr(self, element[0], element[1])
                     if element[1] is not None:
                         self[element[0]] = element[1]
+            elif first_field is not None:
+                self[class_fields[0].name] = first_field
         else:
             for field in class_fields:
                 v = getattr(self, field.name)
@@ -1013,6 +1015,18 @@ class ModelOutput(OrderedDict):
         else:
             return self.to_tuple()[k]
 
+    def __setattr__(self, name, value):
+        if name in self.keys() and value is not None:
+            # Don't call self.__setitem__ to avoid recursion errors
+            super().__setitem__(name, value)
+        super().__setattr__(name, value)
+
+    def __setitem__(self, key, value):
+        # Will raise a KeyException if needed
+        super().__setitem__(key, value)
+        # Don't call self.__setattr__ to avoid recursion errors
+        super().__setattr__(key, value)
+
     def to_tuple(self) -> Tuple[Any]:
         """
         Convert self to a tuple containing all the attributes/keys that are not ``None``.

tests/test_model_output.py

+# coding=utf-8
+# Copyright 2020 The Hugging Face Team.
+#
+# 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.
+
+import unittest
+from dataclasses import dataclass
+from typing import Optional
+
+from transformers.file_utils import ModelOutput
+
+
+@dataclass
+class ModelOutputTest(ModelOutput):
+    a: float
+    b: Optional[float] = None
+    c: Optional[float] = None
+
+
+class ModelOutputTester(unittest.TestCase):
+    def test_get_attributes(self):
+        x = ModelOutputTest(a=30)
+        self.assertEqual(x.a, 30)
+        self.assertIsNone(x.b)
+        self.assertIsNone(x.c)
+        with self.assertRaises(AttributeError):
+            _ = x.d
+
+    def test_index_with_ints_and_slices(self):
+        x = ModelOutputTest(a=30, b=10)
+        self.assertEqual(x[0], 30)
+        self.assertEqual(x[1], 10)
+        self.assertEqual(x[:2], (30, 10))
+        self.assertEqual(x[:], (30, 10))
+
+        x = ModelOutputTest(a=30, c=10)
+        self.assertEqual(x[0], 30)
+        self.assertEqual(x[1], 10)
+        self.assertEqual(x[:2], (30, 10))
+        self.assertEqual(x[:], (30, 10))
+
+    def test_index_with_strings(self):
+        x = ModelOutputTest(a=30, b=10)
+        self.assertEqual(x["a"], 30)
+        self.assertEqual(x["b"], 10)
+        with self.assertRaises(KeyError):
+            _ = x["c"]
+
+        x = ModelOutputTest(a=30, c=10)
+        self.assertEqual(x["a"], 30)
+        self.assertEqual(x["c"], 10)
+        with self.assertRaises(KeyError):
+            _ = x["b"]
+
+    def test_dict_like_properties(self):
+        x = ModelOutputTest(a=30)
+        self.assertEqual(list(x.keys()), ["a"])
+        self.assertEqual(list(x.values()), [30])
+        self.assertEqual(list(x.items()), [("a", 30)])
+        self.assertEqual(list(x), ["a"])
+
+        x = ModelOutputTest(a=30, b=10)
+        self.assertEqual(list(x.keys()), ["a", "b"])
+        self.assertEqual(list(x.values()), [30, 10])
+        self.assertEqual(list(x.items()), [("a", 30), ("b", 10)])
+        self.assertEqual(list(x), ["a", "b"])
+
+        x = ModelOutputTest(a=30, c=10)
+        self.assertEqual(list(x.keys()), ["a", "c"])
+        self.assertEqual(list(x.values()), [30, 10])
+        self.assertEqual(list(x.items()), [("a", 30), ("c", 10)])
+        self.assertEqual(list(x), ["a", "c"])
+
+        with self.assertRaises(Exception):
+            x = x.update({"d": 20})
+        with self.assertRaises(Exception):
+            del x["a"]
+        with self.assertRaises(Exception):
+            _ = x.pop("a")
+        with self.assertRaises(Exception):
+            _ = x.setdefault("d", 32)
+
+    def test_set_attributes(self):
+        x = ModelOutputTest(a=30)
+        x.a = 10
+        self.assertEqual(x.a, 10)
+        self.assertEqual(x["a"], 10)
+
+    def test_set_keys(self):
+        x = ModelOutputTest(a=30)
+        x["a"] = 10
+        self.assertEqual(x.a, 10)
+        self.assertEqual(x["a"], 10)