Warning of hierarchy class constant already defined #362

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1. jimhj commented on Jun 20, 2020

   

   jimhj

   on Jun 20, 2020

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   facing the same warning:
   rails 6.0.0
   closure_tree 7.1.0
2. phlegx commented on Jul 9, 2020

   

   phlegx

   on Jul 9, 2020

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   I have the same warnings.

   ruby: 2.7.1
   rails: 6.0.3.2
   closure_tree: 7.1.0
3. vutran0111 commented on Dec 19, 2020

   

   vutran0111

   on Dec 19, 2020

   Last edited by vutran0111

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   Have the same problem!

   /Users/admin/.rbenv/versions/2.7.2/lib/ruby/gems/2.7.0/gems/closure_tree-7.2.0/lib/closure_tree/support.rb:36: warning: already initialized constant UserHierarchy
   /Users/admin/.rbenv/versions/2.7.2/lib/ruby/gems/2.7.0/gems/closure_tree-7.2.0/lib/closure_tree/support.rb:36: warning: previous definition of UserHierarchy was here
   

   ruby: 2.7.2
   rails: 6.0.3.4
   closure_tree: 7.2.0
4. kevynlebouille commented on Dec 30, 2020

   

   kevynlebouille

   on Dec 30, 2020

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   Have the same problem!

   /Users/kevyn/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/closure_tree-7.2.0/lib/closure_tree/support.rb:36: warning: already initialized constant SectionHierarchy
   /Users/kevyn/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/closure_tree-7.2.0/lib/closure_tree/support.rb:36: warning: previous definition of SectionHierarchy was here
   

   ruby: 2.6.6
   rails: 6.1.0
   closure_tree: 7.2.0
5. simi commented on Feb 24, 2021

   

   simi

   on Feb 24, 2021

   Last edited by simi

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   It is probably related to way how hierarchy class is created on the fly

   closure_tree/lib/closure_tree/support.rb

   Line 36 in 22bbbf1

   hierarchy_class = parent_class.const_set(short_hierarchy_class_name, Class.new(ActiveRecord::Base))

   and Zeitwerk is not unloading it in rails during reload.

   @fxn is there anything we can do about to fix this, any idea?
6. fxn commented on Feb 24, 2021

   

   fxn

   on Feb 24, 2021

   Last edited by fxn

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   Hey! I have written a Hello World app following the README. Let's suppose the model is Tag.

   TagHierarchy is a top-level constant defined by hand in Object. It is no different than Nokogiri, it is a constant in Object that it has not been autoloaded, therefore, it is not reloaded. Since Object is not reloaded (because it has not been autoloaded), the constants it stores that have not been autoloaded remain there untouched, like String.

   I believe there are some options depending on use cases:

   1. If it is expected that users edit the migration of the hierarchy auxiliary table, you may remove_const the constant if present and define it again to have things refreshed.
   2. Alternatively, you can define the constant below model_class, instead of below Object. In that case, when the model class is reloaded, you'll get a fresh new Tag::TagHierarchy again. That is the same principle that applies to autoloaded namespaces, if you have Admin::UsersController, just by unloading Admin, the child UsersController is gone, and you start everything afresh.
   3. If TagHierarchy is internal and remains untouched for all practical purposes, you could just return hierarchy_class if const_defined? (off the top of my head).

   Does that help? Please, do not hesitate to ask more questions!

   👍React with 👍4Reacted by Josef Šimánek, John Lemp, Simon Stearn and Randy Stoller
7. gambala commented on Feb 6, 2022

   

   gambala

   on Feb 6, 2022

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   Any updates here? Still get these warnings in development environment, because of how Zeitwerk work

   ruby: 2.6.1
   rails: 6.1.4.4
   closure_tree: 7.4.0
8. simi commented on Feb 6, 2022

   

   simi

   on Feb 6, 2022

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   @gambala No, this problem wasn't tackled yet (sadly). Xavier (author of Zeitwerk) pointed out 3 possible solutions. Personally I would go with 1. for now. But I'm not 100% sure this is 100% backwards compatible change.

   As a proper solution I think this gem should not define hierarchy model on the fly, but let user/generator create model (backed by classic class in file) and just include ClosureTree::Model concern in there.

   ℹ️ btw. definition happens here

   closure_tree/lib/closure_tree/support.rb

   Line 36 in f3b33f8

   hierarchy_class = parent_class.const_set(short_hierarchy_class_name, Class.new(model_class.superclass))
9. fxn commented on Feb 6, 2022

   

   fxn

   on Feb 6, 2022

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   While this is still open, you can at least avoid the warning if you want. Just depend on Zeitwerk >= 2.5.0, and throw this in an initializer:

   unless Rails.application.config.cache_classes
     # See https://github.com/ClosureTree/closure_tree/issues/362.
     Rails.autoloaders.main.on_unload('Tag') do
       Object.send(:remove_const, 'TagHierarchy')
     end
   end

   ❤️React with ❤️8Reacted by Josef Šimánek, Vitaly, Kevyn Lebouille, Ryan Bates, Kohei🔧, phlegx, Matt and Yauheni Dakuka