Fix most tests

rest_framework/serializers.py

@@ -370,6 +370,12 @@ def _writable_fields(self):
             field for field in self.fields.values() if not field.read_only
         ]
 
+    @cached_property
+    def _read_only_fields(self):
+        return [
+            field for field in self.fields.values() if field.read_only
+        ]
+
     @cached_property
     def _readable_fields(self):
         return [
@@ -431,9 +437,7 @@ def run_validation(self, data=empty):
         if is_empty_value:
             return data
 
-        to_validate = self._read_only_defaults()
-        to_validate.update(data)
-        value = self.to_internal_value(to_validate)
+        value = self.to_internal_value(data)
         try:
             self.run_validators(value)
             value = self.validate(value)
@@ -473,9 +477,11 @@ def to_internal_value(self, data):
 
         ret = OrderedDict()
         errors = OrderedDict()
-        fields = self._writable_fields
+        writable_fields = self._writable_fields
+        read_only_fields = self._read_only_fields
+        read_only_defaults = self._read_only_defaults()
 
-        for field in fields:
+        for field in writable_fields:
             validate_method = getattr(self, 'validate_' + field.field_name, None)
             primitive_value = field.get_value(data)
             try:
@@ -491,6 +497,11 @@ def to_internal_value(self, data):
             else:
                 set_value(ret, field.source_attrs, validated_value)
 
+        for field in read_only_fields:
+            primitive_value = field.get_value(read_only_defaults)
+            if primitive_value is not empty:
+                set_value(ret, field.source_attrs, primitive_value)
+
         if errors:
             raise ValidationError(errors)