Version 2.19.0 causes an infinite loop with the LTS version of activesupport 4.2.11.40 #950

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1. byroot commented on Mar 6, 2026

   

   byroot

   on Mar 6, 2026

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   It's likely a consequence of #941

   I can't promise I can fix it, but I'd appreciate if you could provide a reproduction script so I can investigate the feasibility of fixing it.
2. byroot commented on Mar 6, 2026

   

   byroot

   on Mar 6, 2026

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   I tried to repro with the little information available, but no luck:

   require "bundler/inline"
   
   gemfile do
     gem "activesupport", "4.2.11.3"
     gem "json", "2.19.0"
   end
   
   class Some
     def as_json(...)
       {obj: 1}
     end
   end
   
   puts([{foo: 1, bar: Some.new}].to_json)

   So until I get a repro script or at least some more details, my hands are tied.
3. rwadstein commented on Mar 9, 2026

   

   rwadstein

   on Mar 9, 2026

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   No problem. Thanks for the help. I figured this might be an issue for Rails LTS versions rather than for json since yours works with the last official release. Since Rails LTS are the ones that have extended the last supported version of Rails 4.2, I'll try to reach out to them.
   thanks again.
4. rwadstein

   closed this as completedon Mar 9, 2026
5. rwadstein commented on Mar 9, 2026

   

   rwadstein

   on Mar 9, 2026

   Last edited by rwadstein

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   I was double checking a few things, and found a script that will easily create the problem, but requires going back to ruby 2.7
   Rails LTS supports allows ruby 3+ with the newer versions of BigDecimal, but going back to ruby 2.7 and I can still create the same problem.

   require "bundler/inline"
   
   gemfile do
     gem "activesupport", "4.2.11.3"
     gem "json", "2.19.0"
     gem "bigdecimal", "1.4.4"
   end
   
   require 'active_support/all'
   
   puts([{foo: 1, bar: "asdf"}].to_json)
   
   Traceback (most recent call last):
          16: from /usr/local/bundle/gems/activesupport-4.2.11.3/lib/active_support/core_ext/object/json.rb:34:in 
   ...
           1: from /usr/local/bundle/gems/activesupport-4.2.11.3/lib/active_support/core_ext/object/json.rb:34:in `to_json_with_active_support_encoder'
   SystemStackError (stack level too deep)
6. rwadstein commented on Mar 9, 2026

   

   rwadstein

   on Mar 9, 2026

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   We are actively trying to go to Rails 5, so we can easily just lock it to < 2.19 for now.
   I guess at this point, this is just for context if you decide you want to fix it or not.
7. rwadstein

   reopened this on Mar 9, 2026
8. byroot commented on Mar 9, 2026

   

   byroot

   on Mar 9, 2026

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   Ok I see. I'm afraid I can't fix that, except by reverting what I believe to be an important improvement.

   Rails 4.x is tightly coupled to to_json methods being defined on specific classes.

   You can monkey patch to fix the problem though:

   require "bundler/inline"
   
   gemfile do
     source 'https://rubygems.org'
     gem "stringio"
     gem "activesupport", "4.2.11.3"
     gem "json", "2.19.0"
     gem "bigdecimal", "1.4.4"
     gem "logger"
     gem "base64"
     gem "mutex_m"
     gem "benchmark"
   end
   
   require 'active_support/all'
   
   # Remove custom methods from everywhere but `Object`.
   [Enumerable, Array, FalseClass, Float, Hash, Integer, NilClass, String, TrueClass].each do |klass|
     klass.class_eval do
       remove_method :to_json
       remove_method :to_json_without_active_support_encoder
     end
   end
   
   puts([{foo: 1, bar: "asdf"}].to_json)

   Sorry, I can't do any better than that.

   👍React with 👍1Reacted by Rolf Wadstein
9. byroot

   closed this as not plannedon Mar 9, 2026