#4840 to_xml doesn't work in such case: Event.select('title as t').to_xml - Ruby on Rails

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#4840 ✓resolved

to_xml doesn't work in such case: Event.select('title as t').to_xml

Reported by Cedric Fung | June 12th, 2010 @ 10:11 AM | in 3.0.5

I use ruby 1.9.2 preview3 and rails 3b4

The simple select works well

irb(main):042:0> Event.select('title').limit(3).to_xml
=> "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<events type=\"array\">\n  <event>\n    <title>&#9733;&#31908;&#34880;PARTY&#9733;&#31532;&#19968;&#20987;&#65281;</title>\n  </event>\n  <event>\n    <title> &#33655;&#20848;&#29237;&#22763;&#20843;&#20154;&#32452;&#21512;Electric Barbarian</title>\n  </event>\n  <event>\n    <title>&#27861;&#22269;&#20048;&#38431;1984&#20013;&#22269;&#24033;&#28436;@&#28145;&#22323;&#19968;&#28193;&#22530;</title>\n  </event>\n</events>\n"

but when I try this

irb(main):043:0> Event.select('title as t').limit(3).to_xml
NoMethodError: undefined method type' for nil:NilClass

from /opt/ruby192/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0.beta4/lib/active_support/whiny_nil.rb:48:in `method_missing'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/activerecord-3.0.0.beta4/lib/active_record/serializers/xml_serializer.rb:230:in `compute_type'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/activemodel-3.0.0.beta4/lib/active_model/serializers/xml.rb:20:in `initialize'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/activemodel-3.0.0.beta4/lib/active_model/serializers/xml.rb:73:in `new'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/activemodel-3.0.0.beta4/lib/active_model/serializers/xml.rb:73:in `block in serializable_attributes'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/activemodel-3.0.0.beta4/lib/active_model/serializers/xml.rb:72:in `each'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/activemodel-3.0.0.beta4/lib/active_model/serializers/xml.rb:72:in `map'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/activemodel-3.0.0.beta4/lib/active_model/serializers/xml.rb:72:in `serializable_attributes'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/activemodel-3.0.0.beta4/lib/active_model/serializers/xml.rb:114:in `add_attributes_and_methods'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/activemodel-3.0.0.beta4/lib/active_model/serializers/xml.rb:101:in `block in serialize'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/builder-2.1.2/lib/builder/xmlbase.rb:134:in `call'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/builder-2.1.2/lib/builder/xmlbase.rb:134:in `_nested_structures'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/builder-2.1.2/lib/builder/xmlbase.rb:58:in `method_missing'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/builder-2.1.2/lib/builder/xmlbase.rb:31:in `tag!'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/activemodel-3.0.0.beta4/lib/active_model/serializers/xml.rb:100:in `serialize'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/activerecord-3.0.0.beta4/lib/active_record/serializers/xml_serializer.rb:175:in `to_xml'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0.beta4/lib/active_support/xml_mini.rb:107:in `to_tag'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0.beta4/lib/active_support/core_ext/array/conversions.rb:159:in `block (2 levels) in to_xml'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0.beta4/lib/active_support/core_ext/array/conversions.rb:159:in `each'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0.beta4/lib/active_support/core_ext/array/conversions.rb:159:in `block in to_xml'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/builder-2.1.2/lib/builder/xmlbase.rb:134:in `call'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/builder-2.1.2/lib/builder/xmlbase.rb:134:in `_nested_structures'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/builder-2.1.2/lib/builder/xmlbase.rb:58:in `method_missing'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0.beta4/lib/active_support/core_ext/array/conversions.rb:158:in `to_xml'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/activerecord-3.0.0.beta4/lib/active_record/relation.rb:331:in `method_missing'
from (irb):43
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/railties-3.0.0.beta4/lib/rails/commands/console.rb:47:in `start'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/railties-3.0.0.beta4/lib/rails/commands/console.rb:8:in `start'
from /opt/ruby192/lib/ruby/gems/1.9.1/gems/railties-3.0.0.beta4/lib/rails/commands.rb:23:in `&lt;top (required)&gt;'
from script/rails:9:in `require'
from script/rails:9:in `&lt;main&gt;'irb(main):044:0&gt; </code>

Comments and changes to this ticket

Neeraj Singh June 13th, 2010 @ 03:16 AM
- Tag changed from “select, to_xml” to “ruby19, select, to_xml”
Just to add to the ticket it is working fine with ruby 1.8.7. I am getting following output
```
<?xml version="1.0" encoding="UTF-8"?>
<events type="array">
  <event>
    <t type="NilClass">railsconf</t>
  </event>
</events>
```

knoopx (at gmail) September 30th, 2010 @ 03:02 PM

I'm having similar problems when including associations.

  2) Api::V1::StreamablesController should show details for a movie
     Failure/Error: get(:show, :id => @movie.id, :format => :xml)
     undefined method `type' for nil:NilClass
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.0/lib/active_support/whiny_nil.rb:48:in `method_missing'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.0/lib/active_record/serializers/xml_serializer.rb:230:in `compute_type'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activemodel-3.0.0/lib/active_model/serializers/xml.rb:21:in `initialize'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activemodel-3.0.0/lib/active_model/serializers/xml.rb:74:in `new'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activemodel-3.0.0/lib/active_model/serializers/xml.rb:74:in `block in serializable_attributes'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activemodel-3.0.0/lib/active_model/serializers/xml.rb:73:in `each'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activemodel-3.0.0/lib/active_model/serializers/xml.rb:73:in `map'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activemodel-3.0.0/lib/active_model/serializers/xml.rb:73:in `serializable_attributes'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activemodel-3.0.0/lib/active_model/serializers/xml.rb:115:in `add_attributes_and_methods'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activemodel-3.0.0/lib/active_model/serializers/xml.rb:102:in `block in serialize'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/builder-2.1.2/lib/builder/xmlbase.rb:134:in `call'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/builder-2.1.2/lib/builder/xmlbase.rb:134:in `_nested_structures'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/builder-2.1.2/lib/builder/xmlbase.rb:58:in `method_missing'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/builder-2.1.2/lib/builder/xmlbase.rb:31:in `tag!'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activemodel-3.0.0/lib/active_model/serializers/xml.rb:101:in `serialize'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.0/lib/active_record/serializers/xml_serializer.rb:175:in `to_xml'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.0/lib/active_record/serializers/xml_serializer.rb:218:in `block (2 levels) in add_associations'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.0/lib/active_record/serializers/xml_serializer.rb:210:in `each'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.0/lib/active_record/serializers/xml_serializer.rb:210:in `block in add_associations'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/builder-2.1.2/lib/builder/xmlbase.rb:134:in `call'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/builder-2.1.2/lib/builder/xmlbase.rb:134:in `_nested_structures'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/builder-2.1.2/lib/builder/xmlbase.rb:58:in `method_missing'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/builder-2.1.2/lib/builder/xmlbase.rb:31:in `tag!'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.0/lib/active_record/serializers/xml_serializer.rb:209:in `add_associations'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.0/lib/active_record/serializers/xml_serializer.rb:192:in `block in add_includes'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.0/lib/active_record/serialization.rb:51:in `block in serializable_add_includes'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.0/lib/active_record/serialization.rb:40:in `each'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.0/lib/active_record/serialization.rb:40:in `serializable_add_includes'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.0/lib/active_record/serializers/xml_serializer.rb:191:in `add_includes'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.0/lib/active_record/serializers/xml_serializer.rb:186:in `add_extra_behavior'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activemodel-3.0.0/lib/active_model/serializers/xml.rb:103:in `block in serialize'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/builder-2.1.2/lib/builder/xmlbase.rb:134:in `call'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/builder-2.1.2/lib/builder/xmlbase.rb:134:in `_nested_structures'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/builder-2.1.2/lib/builder/xmlbase.rb:58:in `method_missing'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/builder-2.1.2/lib/builder/xmlbase.rb:31:in `tag!'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activemodel-3.0.0/lib/active_model/serializers/xml.rb:101:in `serialize'
     # /Users/knoopx/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.0/lib/active_record/serializers/xml_serializer.rb:175:in `to_xml'
     # ./app/controllers/api/v1/streamables_controller.rb:16:in `block (2 levels) in show'

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knoopx (at gmail) September 30th, 2010 @ 03:08 PM
It's obvious that the problem is caused by this line:
```
    type = @serializable.class.serialized_attributes.has_key?(name) ?
      super : @serializable.class.columns_hash[name].type
```
If somehow, the resulting SQL is using a dynamic column, @serializable.class.columns_hash[name].type will fail.
In my case I'm getting the exception when evaling @serializable.class.columns_hash["the_parent_id"].type which is not present in the schema due it's a dynamic column.

This exception is thrown even if :skip_types is set to true.
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knoopx (at gmail) September 30th, 2010 @ 03:14 PM
If it works on 1.8 and not in 1.9 it may be due is inheriting attributes that should not be inherited.
José Valim September 30th, 2010 @ 03:29 PM
- State changed from “new” to “open”
- Milestone cleared.
- Assigned user set to “José Valim”
- Importance changed from “” to “Low”
knoopx, could you please provide a patch with tests fixing this error?
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knoopx (at gmail) October 1st, 2010 @ 08:43 AM
This patch makes it behave in ruby-1.9 like using ruby-1.8. I've debugged the attributes on both versions and are exactly the same. when
- 0001-to_xml-doesn-t-work-in-such-case-eventselect-title.patch 1.5 KB
José Valim October 1st, 2010 @ 09:54 AM
The patch needs tests to ensure we won't have regressions.
David Trasbo October 9th, 2010 @ 04:22 PM
- State changed from “open” to “incomplete”
Please add tests to the patch.
Jeremy Kemper October 15th, 2010 @ 11:01 PM
- Milestone set to “3.0.2”
[bulk edit]
Ryan Bigg October 16th, 2010 @ 02:42 AM
- Tag cleared.
Automatic cleanup of spam.
Ryan Bigg November 8th, 2010 @ 01:49 AM
Automatic cleanup of spam.
Santiago Pastorino November 11th, 2010 @ 03:37 AM
knoopx are you able to provide a test? can somebody provide a test case for this?.
Thanks.
Santiago Pastorino November 15th, 2010 @ 09:04 PM
- Milestone cleared.
[bulk edit]
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Cesario November 18th, 2010 @ 08:05 AM
- Tag set to “rails 3.0.0, activecord, serialization, xml”
Here's a patch that includes knoopx's one, and the required test.
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Cesario November 18th, 2010 @ 08:09 AM
I just can't attach any file, that's probably why I kept triggering pull requests instead of discussing the issues here last time... here's my branch on GH https://github.com/cesario/rails/commits/lighthouse-4840
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Cesario November 18th, 2010 @ 08:23 AM
And here's a gist if you wanna have the patch directly

https://gist.github.com/704770
José Valim November 25th, 2010 @ 09:48 AM
- Assigned user changed from “José Valim” to “Aaron Patterson”
Cesario, was this applied already?
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Cesario November 25th, 2010 @ 10:08 AM
Nop, there's a pull request opened as I wanted to clean up a bit my repo https://github.com/rails/rails/pull/115
Aaron Patterson December 15th, 2010 @ 10:02 PM
- State changed from “incomplete” to “resolved”
@Cesario I've merged in your changes. Thanks!
Repository December 15th, 2010 @ 10:04 PM
(from [fe0db2b80588446b34f5f89bbe73f04b88fb06c9]) to_xml doesn't work in such case: Event.select('title as t').to_xml [#4840 state:resolved]

NilClass.type is no longer defined in Ruby 1.9 and causes ActiveRecord::Base.to_xml to fail with message: undefined method type' for nil:NilClass<br/> https://github.com/rails/rails/commit/fe0db2b80588446b34f5f89bbe73f04b88fb06c9
Santiago Pastorino February 12th, 2011 @ 09:58 PM
- Milestone set to “3.0.5”
[bulk edit]