Rails 4.2.2 vs Rails 5.0.2 JSON Storage with PG

[kengreeff]

After updating our app from Rails 4.2.2 to Rails 5 we have noticed that JSON strings are being stored as a string rather than a Hash or Array.

Is there a way we can reproduce the behaviour in Rails 5?

Steps to reproduce

1. Create Model
   bundle exec rails g model OrderItem options:json

2. Run migration
   bundle exec rake db:migrate

3. Open Console
   bundle exec rails c

4. In Console (Rails 4.2.2)

item = OrderItem.new(options: "{\"key\":\"value\"}")
 => #<OrderItem id: nil, options: {"key"=>"value"}>

item.options
 => {"key"=>"value"} 

item.options.is_a?(String)
 => false 

item.options.is_a?(Hash)
 => true

5. In Console (Rails 5.0.2)

item = OrderItem.new(options: "{\"key\":\"value\"}")
 => #<OrderItem id: nil, options: "{\"key\":\"value\"}">

item.options
 => "{\"key\":\"value\"}"

item.options.is_a?(String)
 => true 

item.options.is_a?(Hash)
 => false

Expected behavior

The options attribute should return a hash

Actual behavior

The options attribute returns a string

System configuration

Rails version: 5.0.2
Ruby version: ruby 2.3.1p112
PostgreSQL: 9.4.5

[Erol]

Similar issue to #28285.

[kamipo]

This behavior is because efaa6e4 to fix the issue #24234.
Please use OrderItem.new(options: JSON.parse("{\"key\":\"value\"}")).

[maclover7]

Closing in favor of #28285 to keep similar bug reports in one place.

[kengreeff]

Awesome, thank you. I did see issue #28285 but wasn't sure if that only applied to jsonb columns and that it corrected after calling reload.

@kamipo Will this be the new behaviour going forward or only a temporary fix? I have overwritten the setter methods in my model to check for the JSON string then parse if required for the time being.

[kamipo]

JSON RFC was updated from RFC 4627 to RFC 7159.

https://www.ietf.org/rfc/rfc4627.txt
http://rfc7159.net/rfc7159

Previously JSON-text = object / array, but now value = false / null / true / object / array / number / string.
The new behaviour respects RFC 7159.

[kengreeff]

Do you think this would be worth adding to the upgrade guides (4.2 -> 5) as the behaviour has changed?

[kamipo]

Actually the breaking change was noted in CHANGELOG.md ("Properly accept all valid JSON primitives in the JSON data type.") as a minor breaking change. But adding the guides looks fine to me. Feel free to create a PR.

[kengreeff]

Ok, working on the below.

JSON/JSONB Columns

Rails 5 has been updated to comply with RFC 7159. JSON strings e.g. JSON.stringify() from Javascript are now saved as strings rather than a Hash/Array. To maintain the behaviour from previous versions of Rails you need to parse the JSON string before assigning:

Model.payload = JSON.parse("{\"key\":\"value\"}")

Do you think it is worth mentioning overriding the setter method in the model for the column to keep code DRY?

def payload=(value)
  self[:payload] = value.is_a?(String) ? JSON.parse(value) : value
end

[jwg2s]

We made a quick concern to handle the upgrade a little more gracefully:

module JsonAttrParser
  extend ActiveSupport::Concern

  included do
    columns.select { |column| column.type == :json }.map(&:name).each do |attr|
      define_method("#{attr}=") do |value|
        self[attr] = value.is_a?(String) ? JSON.parse(value) : value
      end
    end
  end
end