Ordering based on SerializerField

[Antony Seedhouse]

As far as I can understand, if you have "renamed" fields in your Serializer class, ordering will only work by specifying the source field name, not the field name that is returned/shown in the frontend

e.g.

class MySerializer(serializers.ModelSerializer):
    impressions = serializers.IntegerField(source='ad_impressions')

?ordering=impressions will not work, but ?ordering=ad_impressions will

Likewise ordering_fields = ('impressions', ) will error

Would it not be desired for this to work by default?

[Antony Seedhouse]

Looking into https://github.com/tomchristie/django-rest-framework/blob/master/rest_framework/filters.py

To get the desired behaviour would require rewriting the field names from get_ordering to their respective source field, either

a) in get_ordering
b) after get_ordering and before remove_invalid_fields
c) in remove_invalid_fields

I learn towards b), which would mean adding something like rewrite_to_source_fields()

Would this be acceptable default behaviour, worthy of a pull request?

[Tom Christie]

> Would it not be desired for this to work by default?

Probably, yes.

[Antony Seedhouse]

Excellent :)

So far I have working method b) that involves building a mapping and using it to replace, which duplicates some of the code from remove_invalid_fields, so I am on the fence about whether it would be better/neater implemented directly in remove_invalid_fields; what do you think?

class SerializerFieldOrderingFilter(OrderingFilter):
    def rewrite_to_source_fields(self, ordering, view):
        # Rewrite Serializer fields to their source fields

        serializer_class = getattr(view, 'serializer_class')
        if serializer_class is None:
            # Nothing to rewrite
            return ordering

        # get mapping of field_name to source
        source_field_mapping = {
            field_name: field.source or field_name for field_name, field in serializer_class().fields.items()
        }

        # rewrite to source field
        for k, field in enumerate(ordering):
            direction = '-' if field[0] == '-' else ''
            if field.lstrip('-') in source_field_mapping.keys():
                ordering[k] = direction + source_field_mapping[field.lstrip('-')]
        return ordering

    def filter_queryset(self, request, queryset, view):
        ordering = self.get_ordering(request)

        if ordering:
            # Rewrite Serializer fields as their source fields
            ordering = self.rewrite_to_source_fields(ordering, view)
            # Skip any incorrect parameters
            ordering = self.remove_invalid_fields(queryset, ordering, view)

        if not ordering:
            # Use 'ordering' attribute by default
            ordering = self.get_default_ordering(view)

        if ordering:
            return queryset.order_by(*ordering)

        return queryset

[Jonathan Liuti]

@tom where do you stand now regarding this issue? Seems pretty odd to offer model field names to the api user whereas they only see serializer field names.

Just wondering if it moved along somewhere else or if I should start implementing something custom on my side ;-)

Cheers,

John.

[Tom Christie]

Not something that's come up on my radar at all anytime lately.

At the moment I don't have any particular opinion on if it's something that should be resolved in REST framework directly or if it should be dealt with in a third party package.

[Jonathan Liuti]

I guess a third-party solution would make sense in regard of how it's done for the search filters. I just think that exposing the limitation of the OrderingFilter in the documentation would help in acknowledging the situation ;-)

Le ven. 12 août 2016 à 10:59, Tom Christie <christ...@gmail.com> a écrit :

Not something that's come up on my radar at all anytime lately.

At the moment I don't have any particular opinion on if it's something that should be resolved in REST framework directly or if it should be dealt with in a third party package.

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