Bug #15718: YAML raises error when dumping strings with UTF32 encoding

• Status: Closed
• Assignee: tenderlovemaking (Aaron Patterson)
• Target version: -
• ruby -v: 2.6.2p247
• Backport: 2.4: UNKNOWN, 2.5: UNKNOWN, 2.6: UNKNOWN
• Tags: ext, encoding

[marcandre (Marc-Andre Lafortune)]

ruby -r yaml -e "p YAML.dump( ''.force_encoding('UTF-32LE') )"

Traceback (most recent call last):
	4: from -e:1:in `<main>'
	3: from /Users/work/.rvm/rubies/ruby-2.6.1/lib/ruby/2.6.0/psych.rb:513:in `dump'
	2: from /Users/work/.rvm/rubies/ruby-2.6.1/lib/ruby/2.6.0/psych/visitors/yaml_tree.rb:118:in `push'
	1: from /Users/work/.rvm/rubies/ruby-2.6.1/lib/ruby/2.6.0/psych/visitors/yaml_tree.rb:136:in `accept'
/Users/work/.rvm/rubies/ruby-2.6.1/lib/ruby/2.6.0/psych/visitors/yaml_tree.rb:298:in `visit_String': incompatible encoding regexp match (US-ASCII regexp with UTF-32LE string) (Encoding::CompatibilityError)

Surprisingly, this works in Ruby 2.4.x, but not in 2.2, 2.3, 2.5 nor 2.6!

[nobu (Nobuyoshi Nakada)]

It may be related to a code range bug.
By adding o.valid_encoding? to Psych::Visitors::YAMLTree#visit_String, the error raises in ruby 24 too.

[rubenochiavone (Ruben Chiavone)]

• File yamldumputf32encodingerror.patch yamldumputf32encodingerror.patch added

Since it relates to mismatch of regex and YAML text encoding a possible fix is to only attempt to match the text when encoding matches or when text encoding is ascii_compatible?. WDYT?

Still I'm not sure why on other versions it works.

Anyhow, I'm adding a patch that reproduces and fixes this issues (hopefully).

[marcandre (Marc-Andre Lafortune)]

rubenochiavone (Ruben Chiavone) wrote:

Since it relates to mismatch of regex and YAML text encoding a possible fix is to only attempt to match the text when encoding matches or when text encoding is ascii_compatible?. WDYT?

What about:

YAML.dump("Hello\nWorld".encode('UTF-32LE'))

or other strings like "123" that need special formatting?

[rubenochiavone (Ruben Chiavone)]

I see. There are other regexp based code similar to what Psych::Visitors::YAMLTree.visit_String does. Not sure if testing for encoding before matching as I initially proposed is the way to go. What else do you suggest that could be a fix? Maybe convert it to US_ASCII or skip non-US_ASCII text altogether?

[jeremyevans0 (Jeremy Evans)]

• Status changed from Open to Feedback
• Assignee set to tenderlovemaking (Aaron Patterson)

I looked into this and ruby YAML uses libyaml, which is a YAML 1.1 implementation. YAML 1.1 does not support UTF-32 encoding; that isn't supported by the YAML spec until YAML 1.2. So I think it is reasonable for YAML.dump to raise Encoding::CompatibilityError for UTF-32 data, and I don't consider this a bug. Assigning to @tenderlovemaking (Aaron Patterson) to make a decision on whether YAML.dump should handle this.

YAML 1.2 is not backwards compatible with YAML 1.1, so I don't think it would be reasonable to switch the YAML library from libyaml to a different library that supports YAML 1.2. I'm not aware of an existing Ruby library that implements YAML 1.2.

[marcandre (Marc-Andre Lafortune)]

Thanks for the investigation @jeremyevans0 (Jeremy Evans) 👍

I'm definitely ok to close this. I don't even recall how I stumbled upon this 😅

[jeremyevans0 (Jeremy Evans)]

• Status changed from Feedback to Closed