Repository: carltongibson/django-filter

Issue:
[2.1.0] BaseCSVWidget.value_from_datadict — AttributeError: 'list' object has no attribute 'split'
I ran into …
```
Traceback (most recent call last):
  [..]
  File "/usr/local/lib/python3.7/site-packages/django/forms/forms.py", line 393, in _clean_fields
    value = field.widget.value_from_datadict(self.data, self.files, self.add_prefix(name))
  File "/usr/local/lib/python3.7/site-packages/django_filters/widgets.py", line 201, in value_from_datadict
    return value.split(',')
AttributeError: 'list' object has no attribute 'split'
```
and found that the code at …
https://github.com/carltongibson/django-filter/blob/1f47e36b614724a8735e0457fa511dcaf5448481/django_filters/widgets.py#L195-L202
… is not robust with regard to `super().value_from_datadict(data, files, name)` returning a list. I need to debug this more but maybe you already know what's going on here?
[2.1.0] BaseCSVWidget.value_from_datadict — AttributeError: 'list' object has no attribute 'split'
I ran into …
```
Traceback (most recent call last):
  [..]
  File "/usr/local/lib/python3.7/site-packages/django/forms/forms.py", line 393, in _clean_fields
    value = field.widget.value_from_datadict(self.data, self.files, self.add_prefix(name))
  File "/usr/local/lib/python3.7/site-packages/django_filters/widgets.py", line 201, in value_from_datadict
    return value.split(',')
AttributeError: 'list' object has no attribute 'split'
```
and found that the code at …
https://github.com/carltongibson/django-filter/blob/1f47e36b614724a8735e0457fa511dcaf5448481/django_filters/widgets.py#L195-L202
… is not robust with regard to `super().value_from_datadict(data, files, name)` returning a list. I need to debug this more but maybe you already know what's going on here?


Discussion:
Hi @moseb. Can you paste the FilterSet code that you're using? The last few lines of the trace back are sufficient to determine why you'd hit this exception.
Full traceback:
```
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/wsgiref/handlers.py", line 137, in run
    self.result = application(self.environ, self.start_response)
  File "/usr/local/lib/python3.7/site-packages/django/contrib/staticfiles/handlers.py", line 65, in __call__
    return self.application(environ, start_response)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/wsgi.py", line 141, in __call__
    response = self.get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/base.py", line 75, in get_response
    response = self._middleware_chain(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 36, in inner
    response = response_for_exception(request, exc)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 90, in response_for_exception
    response = handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/utils/deprecation.py", line 94, in __call__
    response = response or self.get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 36, in inner
    response = response_for_exception(request, exc)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 90, in response_for_exception
    response = handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/utils/deprecation.py", line 94, in __call__
    response = response or self.get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 36, in inner
    response = response_for_exception(request, exc)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 90, in response_for_exception
    response = handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/utils/deprecation.py", line 94, in __call__
    response = response or self.get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 36, in inner
    response = response_for_exception(request, exc)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 90, in response_for_exception
    response = handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/utils/deprecation.py", line 94, in __call__
    response = response or self.get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 36, in inner
    response = response_for_exception(request, exc)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 90, in response_for_exception
    response = handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/utils/deprecation.py", line 94, in __call__
    response = response or self.get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 36, in inner
    response = response_for_exception(request, exc)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 90, in response_for_exception
    response = handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/utils/deprecation.py", line 94, in __call__
    response = response or self.get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 36, in inner
    response = response_for_exception(request, exc)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 90, in response_for_exception
    response = handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django_global_request/middleware.py", line 15, in __call__
    return self.get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 36, in inner
    response = response_for_exception(request, exc)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 90, in response_for_exception
    response = handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/base.py", line 145, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/base.py", line 143, in _get_response
    response = response.render()
  File "/usr/local/lib/python3.7/site-packages/django/template/response.py", line 106, in render
    self.content = self.rendered_content
  File "/usr/local/lib/python3.7/site-packages/rest_framework/response.py", line 72, in rendered_content
    ret = renderer.render(self.data, accepted_media_type, context)
  File "/usr/local/lib/python3.7/site-packages/rest_framework/renderers.py", line 733, in render
    context = self.get_context(data, accepted_media_type, renderer_context)
  File "/usr/local/lib/python3.7/site-packages/rest_framework/renderers.py", line 710, in get_context
    'filter_form': self.get_filter_form(data, view, request),
  File "/usr/local/lib/python3.7/site-packages/rest_framework/renderers.py", line 642, in get_filter_form
    html = backend().to_html(request, queryset, view)
  File "/usr/local/lib/python3.7/site-packages/rest_framework_filters/backends.py", line 52, in to_html
    return super().to_html(request, queryset, view)
  File "/usr/local/lib/python3.7/site-packages/django_filters/rest_framework/backends.py", line 105, in to_html
    return template.render(context, request)
  File "/usr/local/lib/python3.7/site-packages/django/template/backends/django.py", line 61, in render
    return self.template.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 171, in render
    return self._render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 163, in _render
    return self.nodelist.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 937, in render
    bit = node.render_annotated(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 904, in render_annotated
    return self.render(context)
  File "/usr/local/lib/python3.7/site-packages/crispy_forms/templatetags/crispy_forms_tags.py", line 199, in render
    c = self.get_render(context).flatten()
  File "/usr/local/lib/python3.7/site-packages/crispy_forms/templatetags/crispy_forms_tags.py", line 118, in get_render
    actual_form.form_html = helper.render_layout(actual_form, node_context, template_pack=self.template_pack)
  File "/usr/local/lib/python3.7/site-packages/crispy_forms/helper.py", line 308, in render_layout
    template_pack=template_pack
  File "/usr/local/lib/python3.7/site-packages/crispy_forms/layout.py", line 140, in render
    return self.get_rendered_fields(form, form_style, context, template_pack, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/crispy_forms/layout.py", line 104, in get_rendered_fields
    for field in self.fields
  File "/usr/local/lib/python3.7/site-packages/crispy_forms/layout.py", line 104, in <genexpr>
    for field in self.fields
  File "/usr/local/lib/python3.7/site-packages/crispy_forms/utils.py", line 148, in render_field
    html = template.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/backends/django.py", line 61, in render
    return self.template.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 171, in render
    return self._render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 163, in _render
    return self.nodelist.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 937, in render
    bit = node.render_annotated(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 904, in render_annotated
    return self.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/defaulttags.py", line 309, in render
    return nodelist.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 937, in render
    bit = node.render_annotated(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 904, in render_annotated
    return self.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/defaulttags.py", line 309, in render
    return nodelist.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 937, in render
    bit = node.render_annotated(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 904, in render_annotated
    return self.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/defaulttags.py", line 302, in render
    match = condition.eval(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/defaulttags.py", line 876, in eval
    return self.value.resolve(context, ignore_failures=True)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 671, in resolve
    obj = self.var.resolve(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 796, in resolve
    value = self._resolve_lookup(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 837, in _resolve_lookup
    current = getattr(current, bit)
  File "/usr/local/lib/python3.7/site-packages/django/forms/boundfield.py", line 74, in errors
    return self.form.errors.get(self.name, self.form.error_class())
  File "/usr/local/lib/python3.7/site-packages/django/forms/forms.py", line 180, in errors
    self.full_clean()
  File "/usr/local/lib/python3.7/site-packages/django/forms/forms.py", line 381, in full_clean
    self._clean_fields()
  File "/usr/local/lib/python3.7/site-packages/django/forms/forms.py", line 393, in _clean_fields
    value = field.widget.value_from_datadict(self.data, self.files, self.add_prefix(name))
  File "/usr/local/lib/python3.7/site-packages/django_filters/widgets.py", line 201, in value_from_datadict
    return value.split(',')
AttributeError: 'list' object has no attribute 'split'
[12/Jul/2019 13:49:06] "GET /XXXXXXXX/?ordering=first_name HTTP/1.1" 500 59
```
It's from browsing a listing where django-rest-framework generates the code.
> Hi @moseb. Can you paste the FilterSet code that you're using?

To be honest, I haven't found any in that area of the code, yet. It might be all by DRF. Not sure yet.
I'm aware my bug report is not ideal but it's the best I have right now. Sorry!


Your API view should have either a `filterset_class` or `filterset_fields`, or if you're using an older version of django-filter, `filter_class` and `filter_fields`.
I found use of `filter_class` — so I guess you just helped me find that the [migration to django-filter 2.0](https://django-filter.readthedocs.io/en/master/guide/migration.html#migrating-to-2-0) was not properly done to its end. Cool!
Is there something stopping django-filter from detecting pre-2.x leftovers and warning about them, conceptually? Does it warn but I missed it? Would code warning about these be a welcome addition for a pull request?
v2.0 removed a lot of the existing deprecation warnings, so you might try running your test suite against v1.0 and then v1.1 of django-filter.
Assuming this will resolve itself when you update. Come back if not. 
There is reproducible demo of the issue now at https://github.com/moseb/django-filter-issue-1103-demo. Please consider re-opening this issue. Thank you!
Ah, this is related to `ModelMultipleChoiceFilter` not being compatible with the CSV mixin, as well as the `in` lookup. Two separate but related issues here.

You shouldn't need an `in` lookup for m2m fields, since the multiple choice filter already provides similar behavior.
Hi!

> Ah, this is related to `ModelMultipleChoiceFilter` not being compatible with the CSV mixin, as well as the `in` lookup. Two separate but related issues here.

Is there existing tickets on GitHub for these issues?

It sounds like making `BaseCSVWidget.value_from_datadict` more robust as mentioned above alone will not fix the issue? (I don't fully understand the issue yet.)

> You shouldn't need an `in` lookup for m2m fields, since the multiple choice filter already provides similar behavior.

`in` allows checking against multiple values over `exact`. If I cannot use `ìn`, how do I check for multiple values?

PS: Can we re-open this ticket?
> It sounds like making `BaseCSVWidget.value_from_datadict` more robust as mentioned above alone will not fix the issue? (I don't fully understand the issue yet.)

Possibly. If the value is already a list, it should just go ahead and return that list. That said, I don't think it makes sense to mix the CSV-behavior with the `SelectMultiple` widget.

> `in` allows checking against multiple values over `exact`. If I cannot use `ìn`, how do I check for multiple values?

The `ModelMultipleChoiceFilter` constructs an OR query from Q objects. So, if you have a query string like `/api/mymodel?m2m=a&m2m=b`, you would end up with a filter call like

```python
MyModel.objects.filter(Q(m2m='a') | Q(m2m='b'))
```

With the 2.1 release, the `lookup_expr` is now applied to each Q object, so you'd end up with 

```python
MyModel.objects.filter(Q(m2m__in='a') | Q(m2m__in='b'))
```

The above is invalid and would break, however it makes sense for `contains` and other lookups that are intended to work with single values.

So, in short, all you need to do here is use the `exact` lookup for your m2m field.

----

I think the todo here is:
- Make `BaseCSVWidget` compatible with `SelectMultiple` by returning the value if it's already a list. Or if it shouldn't be compatible, we should at least provide a useful error on init.
- Fix `Meta.fields` for m2m. Generating an `in` lookup for `ModelMultipleChoiceFilter` is nonsensical. We should also test what happens for other lookups like `isnull`, which expects a boolean.
Yeah, this still doesn't look like a **bug** but how it all works is under documented I guess... 
I just had this error and its explanation is buried in this thread, so to recap and save a long search for future readers:

`ManyToMany` fields declared in viewsets' `filterset_fields` **must not** contain `in`

A warning at runtime would be very appreciated.
@marcosox Good idea. Happy to look at a PR adding that!
Hi @moseb. Can you paste the FilterSet code that you're using? The last few lines of the trace back are sufficient to determine why you'd hit this exception.
Full traceback:
```
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/wsgiref/handlers.py", line 137, in run
    self.result = application(self.environ, self.start_response)
  File "/usr/local/lib/python3.7/site-packages/django/contrib/staticfiles/handlers.py", line 65, in __call__
    return self.application(environ, start_response)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/wsgi.py", line 141, in __call__
    response = self.get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/base.py", line 75, in get_response
    response = self._middleware_chain(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 36, in inner
    response = response_for_exception(request, exc)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 90, in response_for_exception
    response = handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/utils/deprecation.py", line 94, in __call__
    response = response or self.get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 36, in inner
    response = response_for_exception(request, exc)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 90, in response_for_exception
    response = handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/utils/deprecation.py", line 94, in __call__
    response = response or self.get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 36, in inner
    response = response_for_exception(request, exc)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 90, in response_for_exception
    response = handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/utils/deprecation.py", line 94, in __call__
    response = response or self.get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 36, in inner
    response = response_for_exception(request, exc)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 90, in response_for_exception
    response = handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/utils/deprecation.py", line 94, in __call__
    response = response or self.get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 36, in inner
    response = response_for_exception(request, exc)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 90, in response_for_exception
    response = handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/utils/deprecation.py", line 94, in __call__
    response = response or self.get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 36, in inner
    response = response_for_exception(request, exc)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 90, in response_for_exception
    response = handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/utils/deprecation.py", line 94, in __call__
    response = response or self.get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 36, in inner
    response = response_for_exception(request, exc)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 90, in response_for_exception
    response = handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django_global_request/middleware.py", line 15, in __call__
    return self.get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 36, in inner
    response = response_for_exception(request, exc)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 90, in response_for_exception
    response = handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/base.py", line 145, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/base.py", line 143, in _get_response
    response = response.render()
  File "/usr/local/lib/python3.7/site-packages/django/template/response.py", line 106, in render
    self.content = self.rendered_content
  File "/usr/local/lib/python3.7/site-packages/rest_framework/response.py", line 72, in rendered_content
    ret = renderer.render(self.data, accepted_media_type, context)
  File "/usr/local/lib/python3.7/site-packages/rest_framework/renderers.py", line 733, in render
    context = self.get_context(data, accepted_media_type, renderer_context)
  File "/usr/local/lib/python3.7/site-packages/rest_framework/renderers.py", line 710, in get_context
    'filter_form': self.get_filter_form(data, view, request),
  File "/usr/local/lib/python3.7/site-packages/rest_framework/renderers.py", line 642, in get_filter_form
    html = backend().to_html(request, queryset, view)
  File "/usr/local/lib/python3.7/site-packages/rest_framework_filters/backends.py", line 52, in to_html
    return super().to_html(request, queryset, view)
  File "/usr/local/lib/python3.7/site-packages/django_filters/rest_framework/backends.py", line 105, in to_html
    return template.render(context, request)
  File "/usr/local/lib/python3.7/site-packages/django/template/backends/django.py", line 61, in render
    return self.template.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 171, in render
    return self._render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 163, in _render
    return self.nodelist.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 937, in render
    bit = node.render_annotated(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 904, in render_annotated
    return self.render(context)
  File "/usr/local/lib/python3.7/site-packages/crispy_forms/templatetags/crispy_forms_tags.py", line 199, in render
    c = self.get_render(context).flatten()
  File "/usr/local/lib/python3.7/site-packages/crispy_forms/templatetags/crispy_forms_tags.py", line 118, in get_render
    actual_form.form_html = helper.render_layout(actual_form, node_context, template_pack=self.template_pack)
  File "/usr/local/lib/python3.7/site-packages/crispy_forms/helper.py", line 308, in render_layout
    template_pack=template_pack
  File "/usr/local/lib/python3.7/site-packages/crispy_forms/layout.py", line 140, in render
    return self.get_rendered_fields(form, form_style, context, template_pack, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/crispy_forms/layout.py", line 104, in get_rendered_fields
    for field in self.fields
  File "/usr/local/lib/python3.7/site-packages/crispy_forms/layout.py", line 104, in <genexpr>
    for field in self.fields
  File "/usr/local/lib/python3.7/site-packages/crispy_forms/utils.py", line 148, in render_field
    html = template.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/backends/django.py", line 61, in render
    return self.template.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 171, in render
    return self._render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 163, in _render
    return self.nodelist.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 937, in render
    bit = node.render_annotated(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 904, in render_annotated
    return self.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/defaulttags.py", line 309, in render
    return nodelist.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 937, in render
    bit = node.render_annotated(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 904, in render_annotated
    return self.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/defaulttags.py", line 309, in render
    return nodelist.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 937, in render
    bit = node.render_annotated(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 904, in render_annotated
    return self.render(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/defaulttags.py", line 302, in render
    match = condition.eval(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/defaulttags.py", line 876, in eval
    return self.value.resolve(context, ignore_failures=True)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 671, in resolve
    obj = self.var.resolve(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 796, in resolve
    value = self._resolve_lookup(context)
  File "/usr/local/lib/python3.7/site-packages/django/template/base.py", line 837, in _resolve_lookup
    current = getattr(current, bit)
  File "/usr/local/lib/python3.7/site-packages/django/forms/boundfield.py", line 74, in errors
    return self.form.errors.get(self.name, self.form.error_class())
  File "/usr/local/lib/python3.7/site-packages/django/forms/forms.py", line 180, in errors
    self.full_clean()
  File "/usr/local/lib/python3.7/site-packages/django/forms/forms.py", line 381, in full_clean
    self._clean_fields()
  File "/usr/local/lib/python3.7/site-packages/django/forms/forms.py", line 393, in _clean_fields
    value = field.widget.value_from_datadict(self.data, self.files, self.add_prefix(name))
  File "/usr/local/lib/python3.7/site-packages/django_filters/widgets.py", line 201, in value_from_datadict
    return value.split(',')
AttributeError: 'list' object has no attribute 'split'
[12/Jul/2019 13:49:06] "GET /XXXXXXXX/?ordering=first_name HTTP/1.1" 500 59
```
It's from browsing a listing where django-rest-framework generates the code.
> Hi @moseb. Can you paste the FilterSet code that you're using?

To be honest, I haven't found any in that area of the code, yet. It might be all by DRF. Not sure yet.
I'm aware my bug report is not ideal but it's the best I have right now. Sorry!


Your API view should have either a `filterset_class` or `filterset_fields`, or if you're using an older version of django-filter, `filter_class` and `filter_fields`.
I found use of `filter_class` — so I guess you just helped me find that the [migration to django-filter 2.0](https://django-filter.readthedocs.io/en/master/guide/migration.html#migrating-to-2-0) was not properly done to its end. Cool!
Is there something stopping django-filter from detecting pre-2.x leftovers and warning about them, conceptually? Does it warn but I missed it? Would code warning about these be a welcome addition for a pull request?
v2.0 removed a lot of the existing deprecation warnings, so you might try running your test suite against v1.0 and then v1.1 of django-filter.
Assuming this will resolve itself when you update. Come back if not. 
There is reproducible demo of the issue now at https://github.com/moseb/django-filter-issue-1103-demo. Please consider re-opening this issue. Thank you!
Ah, this is related to `ModelMultipleChoiceFilter` not being compatible with the CSV mixin, as well as the `in` lookup. Two separate but related issues here.

You shouldn't need an `in` lookup for m2m fields, since the multiple choice filter already provides similar behavior.
Hi!

> Ah, this is related to `ModelMultipleChoiceFilter` not being compatible with the CSV mixin, as well as the `in` lookup. Two separate but related issues here.

Is there existing tickets on GitHub for these issues?

It sounds like making `BaseCSVWidget.value_from_datadict` more robust as mentioned above alone will not fix the issue? (I don't fully understand the issue yet.)

> You shouldn't need an `in` lookup for m2m fields, since the multiple choice filter already provides similar behavior.

`in` allows checking against multiple values over `exact`. If I cannot use `ìn`, how do I check for multiple values?

PS: Can we re-open this ticket?
> It sounds like making `BaseCSVWidget.value_from_datadict` more robust as mentioned above alone will not fix the issue? (I don't fully understand the issue yet.)

Possibly. If the value is already a list, it should just go ahead and return that list. That said, I don't think it makes sense to mix the CSV-behavior with the `SelectMultiple` widget.

> `in` allows checking against multiple values over `exact`. If I cannot use `ìn`, how do I check for multiple values?

The `ModelMultipleChoiceFilter` constructs an OR query from Q objects. So, if you have a query string like `/api/mymodel?m2m=a&m2m=b`, you would end up with a filter call like

```python
MyModel.objects.filter(Q(m2m='a') | Q(m2m='b'))
```

With the 2.1 release, the `lookup_expr` is now applied to each Q object, so you'd end up with 

```python
MyModel.objects.filter(Q(m2m__in='a') | Q(m2m__in='b'))
```

The above is invalid and would break, however it makes sense for `contains` and other lookups that are intended to work with single values.

So, in short, all you need to do here is use the `exact` lookup for your m2m field.

----

I think the todo here is:
- Make `BaseCSVWidget` compatible with `SelectMultiple` by returning the value if it's already a list. Or if it shouldn't be compatible, we should at least provide a useful error on init.
- Fix `Meta.fields` for m2m. Generating an `in` lookup for `ModelMultipleChoiceFilter` is nonsensical. We should also test what happens for other lookups like `isnull`, which expects a boolean.
Yeah, this still doesn't look like a **bug** but how it all works is under documented I guess... 
I just had this error and its explanation is buried in this thread, so to recap and save a long search for future readers:

`ManyToMany` fields declared in viewsets' `filterset_fields` **must not** contain `in`

A warning at runtime would be very appreciated.
@marcosox Good idea. Happy to look at a PR adding that!

Resolving patch:
diff --git a/django_filters/widgets.py b/django_filters/widgets.py
--- a/django_filters/widgets.py
+++ b/django_filters/widgets.py
@@ -205,6 +205,10 @@ def value_from_datadict(self, data, files, name):
         if value is not None:
             if value == "":  # empty value should parse as an empty list
                 return []
+            if isinstance(value, list):
+                # since django.forms.widgets.SelectMultiple tries to use getlist
+                # if available, we should return value if it's already an array
+                return value
             return value.split(",")
         return None
 


Test patch:
diff --git a/tests/test_widgets.py b/tests/test_widgets.py
--- a/tests/test_widgets.py
+++ b/tests/test_widgets.py
@@ -383,6 +383,10 @@ class NumberCSVWidget(BaseCSVWidget, NumberInput):
         result = w.value_from_datadict(data, {}, "price")
         self.assertEqual(result, ["1", "2"])
 
+        data = {"price": ["1", "2"]}
+        result = w.value_from_datadict(data, {}, "price")
+        self.assertEqual(result, ["1", "2"])
+
         data = {"price": "1,,2"}
         result = w.value_from_datadict(data, {}, "price")
         self.assertEqual(result, ["1", "", "2"])