Make ValidationError hashable (#65)

* add failing test

* update failing test

* make Message and ValidationError hashable

Author: florimondmanca

tests/test_fields.py

@@ -825,3 +825,9 @@ def test_error_messages_interface():
     validator = Integer()
     value, error = validator.validate_or_error("abc")
     assert error.messages() == [Message(text="Must be a number.", code="type")]
+
+
+def test_validation_error_is_hashable():
+    validator = Integer()
+    _, error = validator.validate_or_error("abc")
+    hash(error)

typesystem/base.py

@@ -78,6 +78,10 @@ def __eq__(self, other: typing.Any) -> bool:
             and self.end_position == other.end_position
         )
 
+    def __hash__(self) -> int:
+        ident = (self.code, tuple(self.index))
+        return hash(ident)
+
     def __repr__(self) -> str:
         class_name = self.__class__.__name__
         index_str = f", index={self.index!r}" if self.index else ""
@@ -183,6 +187,10 @@ def __getitem__(self, key: typing.Any) -> typing.Union[str, dict]:
     def __eq__(self, other: typing.Any) -> bool:
         return isinstance(other, ValidationError) and self._messages == other._messages
 
+    def __hash__(self) -> int:
+        ident = tuple(hash(m) for m in self._messages)
+        return hash(ident)
+
     def __repr__(self) -> str:
         class_name = self.__class__.__name__
         if len(self._messages) == 1 and not self._messages[0].index: