undefined method `delete' for true:TrueClass when executing destroy

[hamann]

This is what I get when I execute 'destroy' on a resource. The resource itself is deleted afterwards.

>> j = PostgresRecoverJob.find("6e3421a41aacd3354c9fb9e7f1d0c854")
=> #<PostgresRecoverJob(recover_jobs/6e3421a41aacd3354c9fb9e7f1d0c854) status="queued" time="2013-04-02 22:04:03 +0200" message="" pct_complete=0 server="sauspiel" target="localhost" backup_id="20130402T171257" completed_at="" id="6e3421a41aacd3354c9fb9e7f1d0c854">
>> j.destroy
NoMethodError: undefined method `delete' for true:TrueClass
    from /Users/hamann/workspace/sauspiel/sauspiel-rails/vendor/bundle/ruby/1.9.1/gems/her-0.5.2/lib/her/middleware/first_level_parse_json.rb:11:in `parse'
    from /Users/hamann/workspace/sauspiel/sauspiel-rails/vendor/bundle/ruby/1.9.1/gems/her-0.5.2/lib/her/middleware/first_level_parse_json.rb:29:in `on_complete'
    from /Users/hamann/workspace/sauspiel/sauspiel-rails/vendor/bundle/ruby/1.9.1/gems/faraday-0.8.6/lib/faraday/response.rb:9:in `block in call'
    from /Users/hamann/workspace/sauspiel/sauspiel-rails/vendor/bundle/ruby/1.9.1/gems/faraday-0.8.6/lib/faraday/response.rb:63:in `on_complete'
    from /Users/hamann/workspace/sauspiel/sauspiel-rails/vendor/bundle/ruby/1.9.1/gems/faraday-0.8.6/lib/faraday/response.rb:8:in `call'
    from /Users/hamann/workspace/sauspiel/sauspiel-rails/vendor/bundle/ruby/1.9.1/gems/faraday-0.8.6/lib/faraday/request/url_encoded.rb:14:in `call'
    from /Users/hamann/workspace/sauspiel/sauspiel-rails/vendor/bundle/ruby/1.9.1/gems/faraday-0.8.6/lib/faraday/connection.rb:247:in `run_request'
    from /Users/hamann/workspace/sauspiel/sauspiel-rails/vendor/bundle/ruby/1.9.1/gems/faraday-0.8.6/lib/faraday/connection.rb:100:in `delete'
    from /Users/hamann/workspace/sauspiel/sauspiel-rails/vendor/bundle/ruby/1.9.1/gems/her-0.5.2/lib/her/api.rb:88:in `request'
    from /Users/hamann/workspace/sauspiel/sauspiel-rails/vendor/bundle/ruby/1.9.1/gems/her-0.5.2/lib/her/model/http.rb:24:in `request'
    from /Users/hamann/workspace/sauspiel/sauspiel-rails/vendor/bundle/ruby/1.9.1/gems/her-0.5.2/lib/her/model/orm.rb:177:in `block in destroy'
    from /Users/hamann/workspace/sauspiel/sauspiel-rails/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.13/lib/active_support/callbacks.rb:403:in `_run__1606273922648791830__destroy__1484856305865657010__callbacks'
    from /Users/hamann/workspace/sauspiel/sauspiel-rails/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.13/lib/active_support/callbacks.rb:405:in `__run_callback'
    from /Users/hamann/workspace/sauspiel/sauspiel-rails/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.13/lib/active_support/callbacks.rb:385:in `_run_destroy_callbacks'
    from /Users/hamann/workspace/sauspiel/sauspiel-rails/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.13/lib/active_support/callbacks.rb:81:in `run_callbacks'
    from /Users/hamann/workspace/sauspiel/sauspiel-rails/vendor/bundle/ruby/1.9.1/gems/her-0.5.2/lib/her/model/orm.rb:176:in `destroy'
    from (irb):2
    from /Users/hamann/workspace/sauspiel/sauspiel-rails/vendor/bundle/ruby/1.9.1/gems/railties-3.2.13/lib/rails/commands/console.rb:47:in `start'
    from /Users/hamann/workspace/sauspiel/sauspiel-rails/vendor/bundle/ruby/1.9.1/gems/railties-3.2.13/lib/rails/commands/console.rb:8:in `start'
    from /Users/hamann/workspace/sauspiel/sauspiel-rails/vendor/bundle/ruby/1.9.1/gems/railties-3.2.13/lib/rails/commands.rb:41:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>

[remi]

What is the response sent back from the API? The only way you could get this error is if the response body would be true:

json = MultiJson.load('true')
json.delete(:errors) # raises NoMethodError: undefined method `delete' for true:TrueClass

I actually wanted to implement some kind of check for this over the weekend to make sure this error doesn’t happen because I thought that only objects or arrays could be sent back from MultiJson.load. But it looks like simple values like true or "foo" are actually valid JSON data.

Anyway, making the endpoint called by #destroy return something like {} for now should do the trick for now. But I’ll come up with something better soon.

[remi]

FWIW, I just pushed a commit in master (30584da) that should provide a better error message when encountering this problem. Will be part of the next release.

[hamann]

You're right, the response is true

Is there a best practice how such a response message should look like?

[remi]

By default, if the server returns an empty hash ({} or { "model_name": {} }, depending on whether you’re using the parse_root_in_json setting), it will keep the model attributes intact and just mark it as destroyed (calling #destroyed? on it will return true).

In my opinion, a good practice would be to return an empty response and send it using the 204 No Content HTTP header. Her will behave the same way as described above.

[remi]

I’m going to close this issue now. Please let me know if you have further questions!

[hamann]

Sorry, but I haven't got time yet to test it. But the case is clear to me and I will change the response messages. Thanks for your work and help!