Why is YAML throwing float ArgumentErrors on strings? - ruby

Question

I have some nested strings in a complex hash that triggers "ArgumentError" exceptions. What's the best practiced way in dealing with this?
require 'yaml'
{
a: 'hello',
b: [{f:'hello',g:Hash.new,i:{a:'hello'}}],
c: {e:"+."}
}.to_yaml #=> `Float': invalid value for Float(): "+" (ArgumentError)
Full error dump:
/Users/XXX/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/psych/scalar_scanner.rb:99:in `Float': invalid value for Float(): "+" (ArgumentError)
from /Users/XXX/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/psych/scalar_scanner.rb:99:in `tokenize'
from /Users/XXX/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/psych/visitors/yaml_tree.rb:272:in `visit_String'
from /Users/XXX/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/psych/visitors/yaml_tree.rb:128:in `accept'
from /Users/XXX/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/psych/visitors/yaml_tree.rb:324:in `block in visit_Hash'
from /Users/XXX/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/psych/visitors/yaml_tree.rb:322:in `each'
from /Users/XXX/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/psych/visitors/yaml_tree.rb:322:in `visit_Hash'
from /Users/XXX/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/psych/visitors/yaml_tree.rb:128:in `accept'
from /Users/XXX/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/psych/visitors/yaml_tree.rb:324:in `block in visit_Hash'
from /Users/XXX/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/psych/visitors/yaml_tree.rb:322:in `each'
from /Users/XXX/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/psych/visitors/yaml_tree.rb:322:in `visit_Hash'
from /Users/XXX/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/psych/visitors/yaml_tree.rb:128:in `accept'
from /Users/XXX/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/psych/visitors/yaml_tree.rb:92:in `push'
from /Users/XXX/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/psych.rb:244:in `dump'
from /Users/XXX/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/psych/core_ext.rb:14:in `psych_to_yaml'

Answer 1

This appears to be a bug in the bundled psych. Patching ~/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/psych/scalar_scanner.rb at line 99 from:
Float(string.gsub(/[,_]|\.$/, ''))
to:
Float(string.gsub(/[,_]|\.$/, '')) rescue ArgumentError
fixes the issue. This is essentially what's in the psych gem as well as the Ruby 1.9 bundled version.
If you'd rather not patch your Ruby, using the psych-1.3.4 gem is another option; just be sure to require 'psych' rather than 'yaml':
gem 'psych', '=1.3.4'
require 'psych'
{a: 'hello', b: [{f:'hello',g:Hash.new,i:{a:'hello'}}], c: {e:"0+."}}.to_yaml
# => "---\n:a: hello\n:b:\n- :f: hello\n :g: {}\n :i:\n :a: hello\n:c:\n :e: 0+.\n"

Answer 2

This can be reproduced with a simpler example:
"+.".to_yaml
This appears to be a bug in the version of psych bundled with ruby 2.0.0 (and other versions, I'm sure):
when FLOAT
if string == '.'
#string_cache[string] = true
string
else
Float(string.gsub(/[,_]|\.$/, ''))
end
The problem is that that "+." looks like a valid floating point number like +.5.
This is fixed in Ruby 2.2.1 (or probably an earlier version), which specifically checks for the case where there may be a leading sign (+ or -):
when FLOAT
if string =~ /\A[-+]?\.\Z/
#string_cache[string] = true
string
else
Float(string.gsub(/[,_]|\.$/, ''))
end