Rails makes Process::Status#to_json less useful

[sunaku]

Hello,

Rails overrides Process::Status#to_json in a way that makes it less useful. For example, outside of Rails, Ruby 1.9.3 would report #<Process::Status: pid 21661 exit 0> but inside Rails test environment it would report {}. See the complete demonstration below.

Thanks for your consideration.

$ ruby -ve 'system "date"; p $?; require "json"; puts JSON.dump([$?])'
ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-linux]
Thu Feb  2 12:49:17 PST 2012
#<Process::Status: pid 25469 exit 0>
["pid 25469 exit 0"]

$ rails new bogus && cd bogus
... output omitted ...

$ bundle exec rails runner 'system "date"; p $?; require "json"; puts JSON.dump([$?])'
Thu Feb  2 12:49:01 PST 2012
#<Process::Status: pid 25401 exit 0>
[{}]

$ bundle list
Gems included by the bundle:
  * actionmailer (3.2.0)
  * actionpack (3.2.0)
  * activemodel (3.2.0)
  * activerecord (3.2.0)
  * activeresource (3.2.0)
  * activesupport (3.2.0)
  * arel (3.0.0)
  * builder (3.0.0)
  * bundler (1.0.21)
  * coffee-rails (3.2.2)
  * coffee-script (2.2.0)
  * coffee-script-source (1.2.0)
  * erubis (2.7.0)
  * execjs (1.3.0)
  * hike (1.2.1)
  * i18n (0.6.0)
  * journey (1.0.1)
  * jquery-rails (2.0.0)
  * json (1.6.5)
  * mail (2.4.1)
  * mime-types (1.17.2)
  * multi_json (1.0.4)
  * polyglot (0.3.3)
  * rack (1.4.1)
  * rack-cache (1.1)
  * rack-ssl (1.3.2)
  * rack-test (0.6.1)
  * rails (3.2.0)
  * railties (3.2.0)
  * rake (0.9.2.2)
  * rdoc (3.12)
  * sass (3.1.12)
  * sass-rails (3.2.4)
  * sprockets (2.1.2)
  * sqlite3 (1.3.5)
  * thor (0.14.6)
  * tilt (1.3.3)
  * treetop (1.4.10)
  * tzinfo (0.3.31)
  * uglifier (1.2.3)

[isaacsanders]

This issue seems to be related to this file: activesupport/lib/active_support/core_ext/object/to_json.rb

I am not sure how to fix this. The file is there for a reason, but breaking this functionality is not good either.

[steveklabnik]

This illustrates (closer to) the root cause:

$ bundle exec rails runner 'system "date"; p $?; require "json"; puts ActiveSupport::JSON.encode($?)'        
Sat Sep 15 15:34:29 MSK 2012
#<Process::Status: pid 45367 exit 0>
{}

Which is defined here.

[steveklabnik]

... which I think is caused by this:

$ bundle exec rails runner 'system "date"; p $?; require "json"; puts $?.instance_values'
Sat Sep 15 15:38:12 MSK 2012
#<Process::Status: pid 45417 exit 0>
{}

[steveklabnik]

... which is caused by this:

$ bundle exec rails runner 'system "date"; p $?; require "json"; puts $?.instance_variables.empty?'
Sat Sep 15 15:39:43 MSK 2012
#<Process::Status: pid 45478 exit 0>
true

(instance_values defined here )

[steveklabnik]

So, Process::Status does not have any instance variables. So I'm not sure what the proper fix is. Theoretically, we could introduce a new core ext that would make fake instance variables for Process::Status, but that sounds really, really, really, really sketchy.

[judofyr]

Why not write a specific as_json for Process::Status?

class Process::Status
  def as_json; { :exitstatus => exitstatus, :pid => pid } end
end

[steveklabnik]

Ha, duh. I blame Russia.