#2753 #to_json behavior still different between Rails 2.3.2.1 and Rails 2-3-stable - Ruby on Rails

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#2753 ✓resolved

#to_json behavior still different between Rails 2.3.2.1 and Rails 2-3-stable

Reported by Cody Fauser | June 3rd, 2009 @ 04:17 PM | in 2.3.3

Ticket #2690 helped the problems with to_json serialization in the Rails 2.3 branch, but the behavior of to_json is still different between Rails 2.3.2.1 and Rails 2.3-stable. The following example illustrates the problem:

class A
  def initialize
    @a, @b = 1, 2
  end
  
  def to_json(options = {})
    @a.to_json(options)
  end
end

class B
  def initialize
    @a = A.new
  end
end

In Rails 2.3.2.1 the output is the following:

b = B.new
b.to_json #=> {"a": 1}

In Rails 2.3-stable the output is:

b = B.new
b.to_json #=> {"a":{"a":1,"b":2}}

The problem is caused by ActiveSupport::JSON.encode calling rails_to_json instead of to_json on the objects. Overridden to_json() methods child objects are never called.

Going forward all objects will have to have a rails_to_json() method, but the problem is that this functionality changed in the stable 2-3 branch.

In Shopify we have monkey patched active_support/json/encoding.rb to call value.to_json() instead of value.rails_to_json() to achieve the same output from Rails 2.3.2.1.

Comments and changes to this ticket

Michael Koziarski June 3rd, 2009 @ 09:23 PM
- Assigned user set to “Rick”
Given this I think we have no choice but to revert the rails_to_json change from 2-3-stable and figure out a plan for deprecation.

It can remain in master of course.
Michael Koziarski June 6th, 2009 @ 05:05 AM
- Milestone changed from “2.x” to “2.3.3”
Jeremy Kemper June 7th, 2009 @ 12:32 AM
- State changed from “new” to “open”
- Assigned user changed from “Rick” to “Jeremy Kemper”
What a headache. Overriding to_json to provide custom JSON representations is a bad API decision. Instead we should be overriding a dump_json method to provide a Hash, Array, etc to encode. Then we don't have to walk the path of
```
class Custom
  def to_json(*strange_internal_state)
```
```
{ :alternate =&gt; 'representation' }.to_json(*strange_internal_state)
```
```
  end
end
```
Instead we have the much cleaner
```
class Custom
  def dump_json(options_hash)
```
```
{ :alternate =&gt; 'representation' }
```
```
  end
end
```
I'm reverting the change in 2-3-stable but will move to this new API in master.
Michael Koziarski June 7th, 2009 @ 04:44 AM
Sounds like an improvement for sure. Not sold on the name, but it
beats the 'return a json string' api that's very brittle.

When you revert this from 2-3-stable move this ticket's milestone to 3.0
Jeremy Kemper June 7th, 2009 @ 06:12 AM
The naming mirrors Marshal's choice of marshal_dump/load
Repository June 8th, 2009 @ 09:24 PM
- State changed from “open” to “resolved”
(from [4a78dae2ab43b5ba94fa06b345e9edeb0305fe44]) Revert rails_to_json -> to_json so we don't break compatibility

[#2753 state:resolved] http://github.com/rails/rails/commit/4a78dae2ab43b5ba94fa06b345e9ed...