feat: Add some changes to ValidationError to support django style vad…

…ation errors (#8863)

rest_framework/exceptions.py

@@ -144,17 +144,30 @@ class ValidationError(APIException):
     status_code = status.HTTP_400_BAD_REQUEST
     default_detail = _('Invalid input.')
     default_code = 'invalid'
+    default_params = {}
 
-    def __init__(self, detail=None, code=None):
+    def __init__(self, detail=None, code=None, params=None):
         if detail is None:
             detail = self.default_detail
         if code is None:
             code = self.default_code
+        if params is None:
+            params = self.default_params
 
         # For validation failures, we may collect many errors together,
         # so the details should always be coerced to a list if not already.
-        if isinstance(detail, tuple):
-            detail = list(detail)
+        if isinstance(detail, str):
+            detail = [detail % params]
+        elif isinstance(detail, ValidationError):
+            detail = detail.detail
+        elif isinstance(detail, (list, tuple)):
+            final_detail = []
+            for detail_item in detail:
+                if isinstance(detail_item, ValidationError):
+                    final_detail += detail_item.detail
+                else:
+                    final_detail += [detail_item % params if isinstance(detail_item, str) else detail_item]
+            detail = final_detail
         elif not isinstance(detail, dict) and not isinstance(detail, list):
             detail = [detail]
 

tests/test_validation_error.py

@@ -109,3 +109,89 @@ def test_validation_error_details(self):
         assert len(error.detail) == 2
         assert str(error.detail[0]) == 'message1'
         assert str(error.detail[1]) == 'message2'
+
+
+class TestValidationErrorWithDjangoStyle(TestCase):
+    def test_validation_error_details(self):
+        error = ValidationError('Invalid value: %(value)s', params={'value': '42'})
+        assert str(error.detail[0]) == 'Invalid value: 42'
+
+    def test_validation_error_details_tuple(self):
+        error = ValidationError(
+            detail=('Invalid value: %(value1)s', 'Invalid value: %(value2)s'),
+            params={'value1': '42', 'value2': '43'},
+        )
+        assert isinstance(error.detail, list)
+        assert len(error.detail) == 2
+        assert str(error.detail[0]) == 'Invalid value: 42'
+        assert str(error.detail[1]) == 'Invalid value: 43'
+
+    def test_validation_error_details_list(self):
+        error = ValidationError(
+            detail=['Invalid value: %(value1)s', 'Invalid value: %(value2)s', ],
+            params={'value1': '42', 'value2': '43'}
+        )
+        assert isinstance(error.detail, list)
+        assert len(error.detail) == 2
+        assert str(error.detail[0]) == 'Invalid value: 42'
+        assert str(error.detail[1]) == 'Invalid value: 43'
+
+    def test_validation_error_details_validation_errors(self):
+        error = ValidationError(
+            detail=ValidationError(
+                detail='Invalid value: %(value1)s',
+                params={'value1': '42'},
+            ),
+        )
+        assert isinstance(error.detail, list)
+        assert len(error.detail) == 1
+        assert str(error.detail[0]) == 'Invalid value: 42'
+
+    def test_validation_error_details_validation_errors_list(self):
+        error = ValidationError(
+            detail=[
+                ValidationError(
+                    detail='Invalid value: %(value1)s',
+                    params={'value1': '42'},
+                ),
+                ValidationError(
+                    detail='Invalid value: %(value2)s',
+                    params={'value2': '43'},
+                ),
+                'Invalid value: %(value3)s'
+            ],
+            params={'value3': '44'}
+        )
+        assert isinstance(error.detail, list)
+        assert len(error.detail) == 3
+        assert str(error.detail[0]) == 'Invalid value: 42'
+        assert str(error.detail[1]) == 'Invalid value: 43'
+        assert str(error.detail[2]) == 'Invalid value: 44'
+
+    def test_validation_error_details_validation_errors_nested_list(self):
+        error = ValidationError(
+            detail=[
+                ValidationError(
+                    detail='Invalid value: %(value1)s',
+                    params={'value1': '42'},
+                ),
+                ValidationError(
+                    detail=[
+                        'Invalid value: %(value2)s',
+                        ValidationError(
+                            detail='Invalid value: %(value3)s',
+                            params={'value3': '44'},
+                        )
+                    ],
+                    params={'value2': '43'},
+                ),
+                'Invalid value: %(value4)s'
+            ],
+            params={'value4': '45'}
+        )
+        assert isinstance(error.detail, list)
+        assert len(error.detail) == 4
+        assert str(error.detail[0]) == 'Invalid value: 42'
+        assert str(error.detail[1]) == 'Invalid value: 43'
+        assert str(error.detail[2]) == 'Invalid value: 44'
+        assert str(error.detail[3]) == 'Invalid value: 45'