Markus

Yeah, that's what I wanted to show and to reproduce (for the developer of this gem, so he has a test case). It looks like the same error you got.

I think the error is because of the [table aliasing](http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#module-ActiveRecord::Associations::ClassMethods-label-Table+Aliasing) in rails on multiple joins. Maybe worth to take a look at.

I have a second (little bit simpler) test case where the same error is triggered even without an `associated_against` `pg_scope` but a regular. In this case it even depends on...

Feel free to review this now, I'll test it for myself for some time to see if I find something more.

I updated the PR to use `ruby2_keywords` and hopefully retain 2.6 compatibility. But still it looks like there is some subtle difference between 2.6 and >= 2.7, because it seems...

I'm using my branch with a ruby 3.1 project and have not encountered any issues yet. Hopefully this will be reviewed/merged and released soon.

Yes, I'm using it in production with ruby 3.1 since end of last year. Before I used it with ruby 2.7 since I opened this PR. I use it mostly...

I opened #192 to hopefully make it compatible with ruby 3, needs some more testing though to make sure it really works like intended!

#192 is compatible with `>= 2.7`, so for all officially supported ruby versions but `2.6`. For `2.6` the [ruby team writes](https://www.ruby-lang.org/en/downloads/): `In security maintenance phase (will EOL soon!)`. The only...

I think this is not possible because it is not JSON:API conformant. You can always amend the serializable hash yourself afterwards though.