Make len lookup for ArrayField use the array_length function

[creative3000]

When you filter by len like in documentation example:

  Post.objects.filter(tags__len=1)

But if you try to annotate something an error pops up example:

 Post.objects.all().annotate(tag_len=F('tags__len'))

It really seems that it should work by default, but instead I needed to use something like this

 Post.objects.all().annotate(tag_len=Func(F('tags'), 1, function='array_length'))

[Tim Graham]

I haven't dug into this. It might be fine. Accepting for further investigation.

[Claude Paroz]

Are you sure the line Post.objects.all().annotate(tag_len=F('tags__len')) is valid?
Where did you read in the documentation a similar construct with a Transform inside a F() expression?

In my opinion, you should have written:

from django.contrib.postgres.fields.array import ArrayLenTransform
Post.objects.all().annotate(tag_len=ArrayLenTransform('tags'))