Django-rest-framework: 3.9: AttributeError when Schema Endpoint requires authentication

[bpereto]

Checklist

• [x] I have verified that that issue exists against the master branch of Django REST framework.
• [x] I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
• [x] This is not a usage question. (Those should be directed to the discussion group instead.)
• [x] This cannot be dealt with as a third party library. (We prefer new functionality to be in the form of third party libraries where possible.)
• [x] I have reduced the issue to the simplest possible case.
• [ ] I have included a failing test as a pull request. (If you are unable to do so we can still accept the issue.)

Steps to reproduce

• Update to 3.9
• Implement Schema Endpoint as described in Announcement: https://www.django-rest-framework.org/community/3.9-announcement/

from rest_framework.schemas import get_schema_view

schema_view = get_schema_view(
    title='Server Monitoring API',
    url='https://www.example.org/api/'
)

urlpatterns = [
    url('^schema.json$', schema_view),
]

• Set Permission IsAuthenticated:

REST_FRAMEWORK = {
    'DEFAULT_PERMISSION_CLASSES': (
        'rest_framework.permissions.IsAuthenticated',
    ),

• Open /schema.json

Expected behavior

• Authorization Error

Actual behavior

Internal Server Error: /schema.json
Traceback (most recent call last):
  File "./.venv/lib/python3.6/site-packages/django/core/handlers/exception.py", line 35, in inner
    response = get_response(request)
  File "./.venv/lib/python3.6/site-packages/django/core/handlers/base.py", line 158, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "./.venv/lib/python3.6/site-packages/django/core/handlers/base.py", line 156, in _get_response
    response = response.render()
  File "./.venv/lib/python3.6/site-packages/django/template/response.py", line 106, in render
    self.content = self.rendered_content
  File "./.venv/lib/python3.6/site-packages/rest_framework/response.py", line 72, in rendered_content
    ret = renderer.render(self.data, accepted_media_type, context)
  File "./.venv/lib/python3.6/site-packages/rest_framework/renderers.py", line 732, in render
    context = self.get_context(data, accepted_media_type, renderer_context)
  File "./.venv/lib/python3.6/site-packages/rest_framework/renderers.py", line 687, in get_context
    'content': self.get_content(renderer, data, accepted_media_type, renderer_context),
  File "./.venv/lib/python3.6/site-packages/rest_framework/renderers.py", line 423, in get_content
    content = renderer.render(data, accepted_media_type, renderer_context)
  File "./.venv/lib/python3.6/site-packages/rest_framework/renderers.py", line 1036, in render
    structure = self.get_structure(data)
  File "./.venv/lib/python3.6/site-packages/rest_framework/renderers.py", line 1016, in get_structure
    'title': data.title,
AttributeError: 'dict' object has no attribute 'title'

.venv/lib/python3.6/site-packages/rest_framework/renderers.py in get_structure
data = {'detail': ErrorDetail(string='Authentication credentials were not provided.', code='not_authenticated')}

[thePaulKelley]

I'm having the same issue after upgrading to 3.9. Am able to work around the issue by logging by other means, but the schema view results in the following error:

```Traceback (most recent call last):
File "/Users/.../anaconda3/envs/datjango/lib/python3.6/site-packages/django/core/handlers/exception.py", line 34, in inner
response = get_response(request)
File "/Users/.../anaconda3/envs/datjango/lib/python3.6/site-packages/django/core/handlers/base.py", line 156, in _get_response
response = self.process_exception_by_middleware(e, request)
File "/Users/.../anaconda3/envs/datjango/lib/python3.6/site-packages/django/core/handlers/base.py", line 154, in _get_response
response = response.render()
File "/Users/.../anaconda3/envs/datjango/lib/python3.6/site-packages/django/template/response.py", line 106, in render
self.content = self.rendered_content
File "/Users/.../anaconda3/envs/datjango/lib/python3.6/site-packages/rest_framework/response.py", line 72, in rendered_content
ret = renderer.render(self.data, accepted_media_type, context)
File "/Users/.../anaconda3/envs/datjango/lib/python3.6/site-packages/rest_framework/renderers.py", line 732, in render
context = self.get_context(data, accepted_media_type, renderer_context)
File "/Users/.../anaconda3/envs/datjango/lib/python3.6/site-packages/rest_framework/renderers.py", line 687, in get_context
'content': self.get_content(renderer, data, accepted_media_type, renderer_context),
File "/Users/.../anaconda3/envs/datjango/lib/python3.6/site-packages/rest_framework/renderers.py", line 423, in get_content
content = renderer.render(data, accepted_media_type, renderer_context)
File "/Users/.../anaconda3/envs/datjango/lib/python3.6/site-packages/rest_framework/renderers.py", line 1036, in render
structure = self.get_structure(data)
File "/Users/.../anaconda3/envs/datjango/lib/python3.6/site-packages/rest_framework/renderers.py", line 1016, in get_structure
'title': data.title,
AttributeError: 'dict' object has no attribute 'title'

I duplicated the error with a clean install of Django==2.1.2 and djangorestframework==3.9.0 with "urls.py" as:

from django.contrib import admin
from django.urls import path, include
from rest_framework.schemas import get_schema_view
from rest_framework.renderers import JSONOpenAPIRenderer

schema_view = get_schema_view(
title='Server Monitoring API',
url='https://www.example.org/api/',
renderer_classes=[JSONOpenAPIRenderer]
)

urlpatterns = [
path('admin/', admin.site.urls),
path('api-auth/', include('rest_framework.urls')),
path('api/', get_schema_view()),
]
```
Let me know if there is any info I can provide to help.

[rpkilby]

Thanks for the minimal reproduction and traceback.

cc @carltongibson?

[carltongibson]

OK, so yes...

This looks to me like a variant of the same issue that came up with 3.6, when we introduced the interactive docs. Basically (I guess) the schema view is picking up DEFAULT_AUTHENTICATION_CLASSES. See e.g. #5399, #5309, #5448...

get_schema_view() takes authentication_classes. First this would be to try passing an empty list in there...

(Does that help?)

[carltongibson]

Is this a duplicate of #6258?

[rpkilby]

@carltongibson this is #6258 😄

[rpkilby]

Brough you this ☕️

[carltongibson]

... this is #6258 😄

Thought it looked relevant.

Brough you this ☕️

Thanks!

[devsnd]

For those that are stuck here, you can just pass the AllowAny permission to the schema_view as a workaround.

schema_view = get_schema_view(
    title="My API",
    permission_classes=[rest_framework.permissions.AllowAny],
)

[shapiromatron]

FYI, I'm still stuck here. I have a custom permission class that doesn't require authentication, so the workaround proposed by @devsnd doesn't work for me. As another alternative fix, I override the default renderer:

from rest_framework import exceptions, renderers

class OpenAPIRendererV2(renderers.OpenAPIRenderer):
    # temporary fix for: https://github.com/encode/django-rest-framework/issues/6258
    def get_structure(self, data):
        if "detail" in data and isinstance(data["detail"], exceptions.ErrorDetail):
            return {"errror": str(data["detail"])}
        return super().get_structure(data)