From: "firedev (Nick O)" <nick@...>
Date: 2013-01-22T21:52:29+09:00
Subject: [ruby-core:51569] [ruby-trunk - Bug #4300] Merge keys not working as expected in psych yaml parser


Issue #4300 has been updated by firedev (Nick O).


Sorry but this isn't fixed as of Ruby 1.9.3p374 (2013-01-15 revision 38858)

https://github.com/tenderlove/psych/issues/8#issuecomment-12541499
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Bug #4300: Merge keys not working as expected in psych yaml parser
https://bugs.ruby-lang.org/issues/4300#change-35527

Author: wr0ngway (Matthew Conway)
Status: Closed
Priority: Normal
Assignee: tenderlovemaking (Aaron Patterson)
Category: ext
Target version: 
ruby -v: ruby 1.9.2p136 (2010-12-25 revision 30365) [x86_64-darwin10.6.0]


=begin
 Psych doesn't seem to support merge keys ( http://yaml.org/type/merge.html ) with alias/anchor the same way that syck does.  I'm not sure if this is intentional or not, but its a pretty useful behavior so I'm filing a bug.  Basically, while psych does allow one to use a merge key to pull a aliased mapping into another mapping, it does not allow one to add other items to that mapping.  Very frequently I have a map that is mostly in common amongst a number of keys, with a subkey that differs, and this bug makes it impossible to achieve this behavior with psych.
 
 For the yaml snippet below:
 
 foo: &foo
   hello: world
 bar:
   << : *foo
   baz: boo
 
 syck produces: {"foo"=>{"hello"=>"world"}, "bar"=>{"hello"=>"world", "baz"=>"boo"}}
 
 psych produces: {"foo"=>{"hello"=>"world"}, "bar"=>{"hello"=>"world"}}
 
 Note that in the yaml 1.1 spec ( http://yaml.org/spec/1.1/#id902561 ) it says "Note that an alias node must not specify any properties or content, as these were already specified at the first occurrence of the node.", however I think this should only apply when doing something like "bar: *foo". When using a merge key, you are creating a new node (which you don't add to), but merging it into a different mapping node - which you should be able to add to.
 
 For reference, also submitted at https://github.com/tenderlove/psych/issues#issue/8/comment/693341
=end



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