Allow ActiveRecord::Base.as_json to accept a frozen Hash #27945

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merged 1 commit into from Feb 8, 2017

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@betesh
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betesh commented Feb 8, 2017 edited

Summary

ActiveRecord::Base.as_json takes an options Hash, which is cloned. The clone is then modified.
Since Object#clone preserves frozen state, a frozen Hash will not work here.

This commit resolves that by changing clone to dup, which does not preserve frozen state.

Other Information

There are many situations where one would want to pass a frozen Hash to as_json. I came across this issue when trying to create a default JSON representation:

class User < ApplicationRecord
  DEFAULT_JSON = { only: [:name, :email] }.freeze

  def as_json(options = nil)
    super(options.presence || DEFAULT_JSON)
  end
end

Doing this in a seemingly innocuous and correct way, I got this stack trace:

 RuntimeError:
   can't modify frozen Hash
# ~/.rvm/gems/ruby-2.3.0/gems/activerecord-5.0.1/lib/active_record/serialization.rb:14:in `serializable_hash'
# ~/.rvm/gems/ruby-2.3.0/gems/activemodel-5.0.1/lib/active_model/serializers/json.rb:99:in `as_json'
# ./app/models/user.rb:5:in `as_json'
@schneems schneems was assigned by rails-bot Feb 8, 2017
@rails-bot

Thanks for the pull request, and welcome! The Rails team is excited to review your changes, and you should hear from @schneems (or someone else) soon.

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@rafaelfranca

Could you add a CHANGELOG entry?

@dennisbaskin

👍

@betesh
Contributor
betesh commented Feb 8, 2017

Changelog entry added

@rafaelfranca

Could you squash your commits please?

@betesh
Contributor
betesh commented Feb 8, 2017

There's a Rubocop violation. Should I squash the fix?

@rafaelfranca
Member
rafaelfranca commented Feb 8, 2017 edited

If it is in your changeset, yes.

@betesh betesh Allow ActiveRecord::Base.as_json to accept a frozen Hash
c01f31f
@betesh
Contributor
betesh commented Feb 8, 2017

Yes, it's in my changeset. Sorry that wasn't clear. Done.

@rafaelfranca
Member

Backported in 0f338df.

@rafaelfranca rafaelfranca merged commit c01f31f into rails:master Feb 8, 2017

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