YAML for Ruby: How to turn off the boolean interpretations?


#1

I have YAML documents generated in Perl and Python that I process with
Ruby.

Problem: Ruby wants to auto-interpret boolean flagged words, example:


words:

  • yes
  • put
  • it
  • on
  • the
  • off
  • setting

gets loaded in Ruby as

[true, “put”, “it”, true, “the”, false, “setting”]

Basically the latest Perl and Python YAML modules I could find won’t
quote some of the words that Ruby’s YAML would. (Things like on, off,
yes, no, +) Perhaps they conform to a different version of the YAML
spec. I find the incompatibility a bit frustrating. I can and have
easily hacked the other modules to do the compatible thing but there
are political admin maintenance issues surrounding my patching all the
company computers with this.

I’ll not comment right now on whether I think it was a good idea to
flag these items as special to begin with. I’d just like to know if
there’s a simple module over-ride hack or module parameter setting that
I can set or clip into my scripts to deal with this problem.

Thanks.


#2

mikshir wrote:

Problem: Ruby wants to auto-interpret boolean flagged words, […]

Hi Mikshir,

Hadn’t heard about those :-? Interesting.

I’ll not comment right now on whether I think it was a good idea to
flag these items as special to begin with. I’d just like to know if
there’s a simple module over-ride hack or module parameter setting that
I can set or clip into my scripts to deal with this problem.

Thanks.

This isn’t anything official, so caution is recommended.

Successive changes to YAML.rb mean that I’ve had to stitch
two fixes. The relevant one should auto-select and it
seems to work for the following Rubys:

   1.8.0 (2003-08-30)
   1.8.2 (2004-12-25)
   1.8.3 (2005-07-22)
   1.8.4 (2005-12-01)
   1.9.0 (2005-10-31)

It re-categorises all bool types as normal strings and
doesn’t touch any other types.

Note that, as well as inserting the module addition in your
scripts, you must use:
YAML.parse(foo).transform
^^^^^^^^^^^^^^^^^^^^^^^^^
in place of YAML.load
http://yaml4r.sourceforge.net/doc/class/yaml_parser_parse_method.htm

<fix/test below> - email me if any problem(s).

daz

require ‘yaml’

#----------------------------------------------------------------------
module YAML::Syck
BOOL_RE = /bool#\w+\z/
if defined?(Loader)
class Loader
alias_method :o_transfer, :transfer
def transfer(type_id, val)
(String === type_id) and type_id.gsub!(BOOL_RE, ‘str’)
o_transfer(type_id, val)
end
end
else
class Node
alias_method :o_transform, :transform
def transform
kind == :scalar and self.type_id = type_id.gsub(BOOL_RE, ‘str’)
o_transform
end
end
end
end
#----------------------------------------------------------------------

hobj = YAML.parse(<<EoS).transform

words:

  • yes
  • put
  • it
  • on
  • the
  • off
  • setting
    EoS

if hobj[‘words’] == %w{ yes put it on the off setting }
puts ’ ***—> S U C C E S S <—***’
else
p hobj
end


#3

On Dec 9, 2005, at 3:57 PM, mikshir wrote:

  • on
    yes, no, +) Perhaps they conform to a different version of the YAML

Thanks.

Well, I was looking at the YAML site, and apparently yes/no on/off
are part of a draft specification, it looks like ruby is just ahead
of the curve, so to speak.

http://yaml.org/type/bool.html

This of course, fails to help you.

The only solution I could come up with, in a word, sucks.

require ‘yaml’

test = YAML.parse(FIle.read(“test.yml”)) # where test.yml contains
that —\n words: -yes -no etc.
test.children[0].value.each do |x|
if x.type_id =~ /bool#(?:yes|no)\z/
x.type_id = “tag:yaml.org,2002:str”
end
end

results = test.transform #=> {“words”=>[“yes”, “put”, “it”, “on”,
“the”, “off”, “setting”]}

Of course this iteration will only work for that file, since I made
some massive assumptions about the structure. Your other option is to
do a search and replace on the yess, ons,offs, etc and quote them
before parsing.


#4

I wrote:

http://yaml4r.sourceforge.net/doc/class/yaml_parser_parse_method.htm

Huh? It changed in transit :confused: Should be:
http://yaml4r.sourceforge.net/doc/class/yaml_parse_method.htm


#5

On Dec 10, 2005, at 2:16 AM, removed_email_address@domain.invalid wrote:

why not simply conform to the spec? :

I believe that the documents are being generated by Python and/or
Perl and he is (for whatever reason) not allowed to mess with that part.


#6

On Sat, 10 Dec 2005, mikshir wrote:

  • on
    yes, no, +) Perhaps they conform to a different version of the YAML
    Thanks.
    why not simply conform to the spec? :
 harp:~ > cat a.rb
 doc = <<-yaml
 ---
 "words":
  - "yes"
  - "put"
  - "it"
  - "on"
  - "the"
  - "off"
  - "setting"
 yaml

 doc = STDIN.read unless STDIN.tty?

 require "yaml" and y(YAML::load(doc))


 harp:~ > ruby a.rb
 words:
 - "yes"
 - put
 - it
 - "on"
 - the
 - "off"
 - setting


 harp:~ > ruby a.rb|ruby a.rb
 words:
 - "yes"
 - put
 - it
 - "on"
 - the
 - "off"
 - setting

as you can see these words need to be quoted to be handled correctly -
basically the error is both in the person(s) writing the docs and in the
other
decoders. i’ll bet a quoted “yes” or “no” works in perl and python
decoders
too though.

regards.

-a


#7

Thanks for the followups, gang.

Yes, I have my own modified version of PyYaml to make it conform to the
latest Ruby implemention. (I haven’t done this for the Perl YAML
module yet.) The immediate issue is that for certain reasons I can’t
update the modules system-wide and so I was looking for a quick and
easy user-script solution; like throwing in some re-definitions,
overrides, or extensions to force in some backwards compatability and
something I can throw in a library or with a switch.

Quoting the flagged words does the right thing (forces them to be
strings) and pre/post processing all Python and Perl generated Yaml
docs has been a stop-gap measure but is clumsy or not convenient.

Anyhow, thanks very much Daz. I will test out your method. /salute