Fix get_template_context to handle also lists

rest_framework/renderers.py

@@ -171,6 +171,10 @@ def resolve_template(self, template_names):
 
     def get_template_context(self, data, renderer_context):
         response = renderer_context['response']
+        # in case a ValidationError is caught the data parameter may be a list
+        # see rest_framework.views.exception_handler
+        if isinstance(data, list):
+            return {'details': data, 'status_code': response.status_code}
         if response.exception:
             data['status_code'] = response.status_code
         return data

tests/test_htmlrenderer.py

@@ -8,6 +8,7 @@
 
 from rest_framework import status
 from rest_framework.decorators import api_view, renderer_classes
+from rest_framework.exceptions import ValidationError
 from rest_framework.renderers import TemplateHTMLRenderer
 from rest_framework.response import Response
 
@@ -34,10 +35,17 @@ def not_found(request):
     raise Http404()
 
 
+@api_view(('GET',))
+@renderer_classes((TemplateHTMLRenderer,))
+def validation_error(request):
+    raise ValidationError('error')
+
+
 urlpatterns = [
     path('', example),
     path('permission_denied', permission_denied),
     path('not_found', not_found),
+    path('validation_error', validation_error),
 ]
 
 
@@ -91,6 +99,12 @@ def test_permission_denied_html_view(self):
         self.assertEqual(response.content, b"403 Forbidden")
         self.assertEqual(response['Content-Type'], 'text/html; charset=utf-8')
 
+    def test_validation_error_html_view(self):
+        response = self.client.get('/validation_error')
+        self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
+        self.assertEqual(response.content, b"400 Bad Request")
+        self.assertEqual(response['Content-Type'], 'text/html; charset=utf-8')
+
     # 2 tests below are based on order of if statements in corresponding method
     # of TemplateHTMLRenderer
     def test_get_template_names_returns_own_template_name(self):