remove base class from belongs_to polymorphic association

[dilpreet92]

Fix polymorphic true with inheritance.
Before this PR, it is used to store in type column the class which is directly inherited from the AR::Base.

Example:

 class Asset < ActiveRecord::Base
   belongs_to :attachable, polymorphic: true
 end

 class Post < ActiveRecord::Base
   # Post doesn't have a type column and is not implemented as STI
  has_many :assets, as: :attachable, dependent: :destroy
 end

 class GuestPost < Post
  #Guest Post is inherited From Post
 end

 class MemberPost < Post
  #Member Post is inherited From Post
 end

Example: asset = Asset.new(attachable: GuestPost.new)
                asset.attachable_type would always be equal to 'Post'

After this change, type column can have any class (descendant of the AR::Base)
Now attachable_type can be Post, GuestPost or MemberPost
Example:

asset = Asset.new(attachable: GuestPost.new)
asset.attachable_type would  be equal to 'GuestPost'

[al2o3cr]

This is related to (but not the same issue as) the whole gang of issues referenced here on #20893.

It's different because Post is not STI, so the subclass of Post that a particular row in the posts table represents is determined by how the object is referenced, not by the row alone. In the example given, an Asset with post_id: 42, post_type: 'GuestPost' will get a different flavor of Post object than an Asset with post_id: 42, post_type: 'MemberPost'.

[opsydev]

+1 Would love to see this be merged in.

[maclover7]

Please rebase.

[dilpreet92]

Done

[arthurnn]

@rafaelfranca WDYT ? I think the use case make sense. I am curious tho if you can think a situation why this would not work.

[dilpreet92]

@maclover7 @rafaelfranca - Any suggestions on this.?

[njakobsen]

Was just bitten by this today. The behaviour suggested in the PR seems like it's the most obvious. You build an association off of a subclass, the type column should be that subclass. This is especially useful if the original record is no longer available to read the type from (I'm restoring deleted records)

[chrisdpeters]

I was also bitten by this this week. I have a model class that extends a class from a gem. The base class name from the gem is being inserted into the polymorphic _type column instead of the real class name.

[boblail]

+1 😁

[ajays1991]

+1 👍

[ajays1991]

any update on this if this is planned to be merged in near future

[rafaelfranca]

Can you rebase the branch?

[ajays1991]

@dilpreet92 sorry i am not able to see build error on codeclimate. looks like i its not an open port. let me know if you need spare hand to fix this and getting see in master like me

[dilpreet92]

@ajays1991 sure, thanks for the help

[rails-bot]

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