Revert 3288 (#5313)

* Add regression test for #2505. Thanks @pySilver!

* Add regression test for #5087

* Revert "Cached the field's root and context property."

This reverts commit 79200580.

rest_framework/fields.py

@@ -26,7 +26,6 @@ from django.utils.dateparse import (
 from django.utils.duration import duration_string
 from django.utils.encoding import is_protected_type, smart_text
 from django.utils.formats import localize_input, sanitize_separators
-from django.utils.functional import cached_property
 from django.utils.ipv6 import clean_ipv6_address
 from django.utils.timezone import utc
 from django.utils.translation import ugettext_lazy as _
@@ -586,7 +585,7 @@ class Field(object):
         message_string = msg.format(**kwargs)
         raise ValidationError(message_string, code=key)
 
-    @cached_property
+    @property
     def root(self):
         """
         Returns the top-level serializer for this field.
@@ -596,7 +595,7 @@ class Field(object):
             root = root.parent
         return root
 
-    @cached_property
+    @property
     def context(self):
         """
         Returns the context as passed to the root serializer on initialization.

tests/test_fields.py

@@ -502,6 +502,16 @@ class TestCreateOnlyDefault:
         assert serializer.validated_data['context_set'] == 'success'
 
 
+class Test5087Regression:
+    def test_parent_binding(self):
+        parent = serializers.Serializer()
+        field = serializers.CharField()
+
+        assert field.root is field
+        field.bind('name', parent)
+        assert field.root is parent
+
+
 # Tests for field input and output values.
 # ----------------------------------------
 

tests/test_serializer.py

@@ -469,6 +469,22 @@ class TestSerializerValidationWithCompiledRegexField:
         assert serializer.errors == {}
 
 
+class Test2505Regression:
+    def test_serializer_context(self):
+        class NestedSerializer(serializers.Serializer):
+            def __init__(self, *args, **kwargs):
+                super(NestedSerializer, self).__init__(*args, **kwargs)
+                # .context should not cache
+                self.context
+
+        class ParentSerializer(serializers.Serializer):
+            nested = NestedSerializer()
+
+        serializer = ParentSerializer(data={}, context={'foo': 'bar'})
+        assert serializer.context == {'foo': 'bar'}
+        assert serializer.fields['nested'].context == {'foo': 'bar'}
+
+
 class Test4606Regression:
     def setup(self):
         class ExampleSerializer(serializers.Serializer):