Handle tuples same as lists in ValidationError detail context (#7647)

rest_framework/exceptions.py

@@ -20,7 +20,7 @@ def _get_error_details(data, default_code=None):
     Descend into a nested data structure, forcing any
     lazy translation strings or strings into `ErrorDetail`.
     """
-    if isinstance(data, list):
+    if isinstance(data, (list, tuple)):
         ret = [
             _get_error_details(item, default_code) for item in data
         ]
@@ -150,7 +150,9 @@ class ValidationError(APIException):
 
         # For validation failures, we may collect many errors together,
         # so the details should always be coerced to a list if not already.
-        if not isinstance(detail, dict) and not isinstance(detail, list):
+        if isinstance(detail, tuple):
+            detail = list(detail)
+        elif not isinstance(detail, dict) and not isinstance(detail, list):
             detail = [detail]
 
         self.detail = _get_error_details(detail, code)

tests/test_validation_error.py

@@ -2,6 +2,7 @@ from django.test import TestCase
 
 from rest_framework import serializers, status
 from rest_framework.decorators import api_view
+from rest_framework.exceptions import ValidationError
 from rest_framework.response import Response
 from rest_framework.settings import api_settings
 from rest_framework.test import APIRequestFactory
@@ -99,3 +100,12 @@ class TestValidationErrorWithCodes(TestCase):
         response = view(request)
         assert response.status_code == status.HTTP_400_BAD_REQUEST
         assert response.data == self.expected_response_data
+
+
+class TestValidationErrorConvertsTuplesToLists(TestCase):
+    def test_validation_error_details(self):
+        error = ValidationError(detail=('message1', 'message2'))
+        assert isinstance(error.detail, list)
+        assert len(error.detail) == 2
+        assert str(error.detail[0]) == 'message1'
+        assert str(error.detail[1]) == 'message2'