Rejig ErrorMessages, to prefer code= directly on ValidationError

rest_framework/exceptions.py

@@ -10,7 +10,6 @@ import math
 
 from django.utils import six
 from django.utils.encoding import force_text
-from django.utils.functional import Promise
 from django.utils.translation import ugettext_lazy as _
 from django.utils.translation import ungettext
 
@@ -18,21 +17,21 @@ from rest_framework import status
 from rest_framework.utils.serializer_helpers import ReturnDict, ReturnList
 
 
-def _force_text_recursive(data):
+def _force_text_recursive(data, code=None):
     """
     Descend into a nested data structure, forcing any
-    lazy translation strings into plain text.
+    lazy translation strings or strings into `ErrorMessage`.
     """
     if isinstance(data, list):
         ret = [
-            _force_text_recursive(item) for item in data
+            _force_text_recursive(item, code) for item in data
         ]
         if isinstance(data, ReturnList):
             return ReturnList(ret, serializer=data.serializer)
         return ret
     elif isinstance(data, dict):
         ret = {
-            key: _force_text_recursive(value)
+            key: _force_text_recursive(value, code)
             for key, value in data.items()
         }
         if isinstance(data, ReturnDict):
@@ -40,7 +39,7 @@ def _force_text_recursive(data):
         return ret
 
     text = force_text(data)
-    code = getattr(data, 'code', 'invalid')
+    code = getattr(data, 'code', code or 'invalid')
     return ErrorMessage(text, code)
 
 
@@ -82,18 +81,11 @@ class ValidationError(APIException):
     status_code = status.HTTP_400_BAD_REQUEST
 
     def __init__(self, detail, code=None):
-        if code is not None:
-            assert isinstance(detail, six.string_types + (Promise,)), (
-                "When providing a 'code', the detail must be a string argument. "
-                "Use 'ErrorMessage' to set the code for a composite ValidationError"
-            )
-            detail = ErrorMessage(detail, code)
-
         # For validation errors the 'detail' key is always required.
         # The details should always be coerced to a list if not already.
         if not isinstance(detail, dict) and not isinstance(detail, list):
             detail = [detail]
-        self.detail = _force_text_recursive(detail)
+        self.detail = _force_text_recursive(detail, code=code)
 
     def __str__(self):
         return six.text_type(self.detail)

rest_framework/serializers.py

@@ -423,8 +423,8 @@ class Serializer(BaseSerializer):
                 datatype=type(data).__name__
             )
             raise ValidationError({
-                api_settings.NON_FIELD_ERRORS_KEY: [ErrorMessage(message, code='invalid')]
-            })
+                api_settings.NON_FIELD_ERRORS_KEY: [message]
+            }, code='invalid')
 
         ret = OrderedDict()
         errors = OrderedDict()
@@ -440,7 +440,7 @@ class Serializer(BaseSerializer):
             except ValidationError as exc:
                 errors[field.field_name] = exc.detail
             except DjangoValidationError as exc:
-                errors[field.field_name] = list(exc.messages)
+                errors[field.field_name] = get_validation_error_detail(exc)
             except SkipField:
                 pass
             else:
@@ -580,14 +580,14 @@ class ListSerializer(BaseSerializer):
                 input_type=type(data).__name__
             )
             raise ValidationError({
-                api_settings.NON_FIELD_ERRORS_KEY: [ErrorMessage(message, code='not_a_list')]
-            })
+                api_settings.NON_FIELD_ERRORS_KEY: [message]
+            }, code='not_a_list')
 
         if not self.allow_empty and len(data) == 0:
             message = self.error_messages['empty']
             raise ValidationError({
-                api_settings.NON_FIELD_ERRORS_KEY: [ErrorMessage(message, code='empty')]
-            })
+                api_settings.NON_FIELD_ERRORS_KEY: [message]
+            }, code='empty')
 
         ret = []
         errors = []

rest_framework/validators.py

@@ -12,7 +12,7 @@ from django.db import DataError
 from django.utils.translation import ugettext_lazy as _
 
 from rest_framework.compat import unicode_to_repr
-from rest_framework.exceptions import ErrorMessage, ValidationError
+from rest_framework.exceptions import ValidationError
 from rest_framework.utils.representation import smart_repr
 
 
@@ -121,12 +121,12 @@ class UniqueTogetherValidator(object):
             return
 
         missing_items = {
-            field_name: ErrorMessage(self.missing_message, code='required')
+            field_name: self.missing_message
             for field_name in self.fields
             if field_name not in attrs
         }
         if missing_items:
-            raise ValidationError(missing_items)
+            raise ValidationError(missing_items, code='required')
 
     def filter_queryset(self, attrs, queryset):
         """
@@ -206,12 +206,12 @@ class BaseUniqueForValidator(object):
         'required' state on the fields they are applied to.
         """
         missing_items = {
-            field_name: ErrorMessage(self.missing_message, code='required')
+            field_name: self.missing_message
             for field_name in [self.field, self.date_field]
             if field_name not in attrs
         }
         if missing_items:
-            raise ValidationError(missing_items)
+            raise ValidationError(missing_items, code='required')
 
     def filter_queryset(self, attrs, queryset):
         raise NotImplementedError('`filter_queryset` must be implemented.')
@@ -233,8 +233,8 @@ class BaseUniqueForValidator(object):
         if qs_exists(queryset):
             message = self.message.format(date_field=self.date_field)
             raise ValidationError({
-                self.field: ErrorMessage(message, code='unique')
-            })
+                self.field: message
+            }, code='unique')
 
     def __repr__(self):
         return unicode_to_repr('<%s(queryset=%s, field=%s, date_field=%s)>' % (