"parent" does not work if the primary key is not :id

[AlvaroMaceda]

When upgrading from 3.2.1 to 4.2.1, I've found that the gem can't work with non-standard primary key names:

class NonStandard < ApplicationRecord
  self.primary_key =   "whatever"
end

NonStandard.first.parent 
*** ActiveRecord::StatementInvalid Exception: Mysql2::Error: Unknown column 'non_standard.id' in 'where clause'

In this case it's caused because the new version is doing a find_by id: instead of a find:

def parent
    if has_parent?
      unscoped_where do |scope|
        scope.find_by id: parent_id
      end
    end
  end

Old code:

def parent
  unscoped_find(parent_id) if ancestors?
end
def unscoped_find id
  unscoped_where do |scope|
    scope.find id
  end
end

[kbrock]

So the find_by avoided throwing an exception that the find had.
I could have sworn that looking up by id would swap in the primary key when there a non standard primary_key was used.

Do you want to put an a pr that uses class.primary_key => parent_id?

[founder3000]

Oooooooof. I can't use this any more. I want to store multiple parallel ancestries in a single table under separate FKs. Huge block now.

[kbrock]

yea. that is part of the original design.
I have ideas to remove this constraint but it introduces a breaking change (and still needs lot more work) so that has stalled me for a few years.

Not sure your time frame but maybe closure trees will meet your need.