[ruby-core:72853] [Ruby trunk - Bug #11988] [Assigned] YAML.dump doesn't quote string starting with 0 which will be recognized as float in YAML 1.2

Issue #11988 has been updated by Yui NARUSE.

Status changed from Open to Assigned
Assignee set to Aaron Patterson
Backport changed from 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN to 2.0.0: REQUIRED, 2.1: REQUIRED, 2.2: REQUIRED, 2.3: REQUIRED

I found it is psych's issue.
Following fixes this (but may be it is fixed in Psych::ScalarScanner#tokenize.

```diff
diff --git a/ext/psych/lib/psych/visitors/yaml_tree.rb b/ext/psych/lib/psych/visitors/yaml_tree.rb
index 7c40050..15cd89c 100644
--- a/ext/psych/lib/psych/visitors/yaml_tree.rb
+++ b/ext/psych/lib/psych/visitors/yaml_tree.rb
@@ -331,7 +331,8 @@ def visit_String o
           style = Nodes::Scalar::FOLDED
         elsif o =~ /^[^[:word:]][^"]*$/
           style = Nodes::Scalar::DOUBLE_QUOTED
-        elsif not String === @ss.tokenize(o)
+        elsif not String === @ss.tokenize(o) or /\A0[0-7]*[89]/ =~ o
+          p @ss
           style = Nodes::Scalar::SINGLE_QUOTED
         end
```

----------------------------------------
Bug #11988: YAML.dump doesn't quote string starting with 0 which will be recognized as float in YAML 1.2
https://bugs.ruby-lang.org/issues/11988#change-56089

* Author: Sadayuki Furuhashi
* Status: Assigned
* Priority: Normal
* Assignee: Aaron Patterson
* ruby -v: ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-darwin14]
* Backport: 2.0.0: REQUIRED, 2.1: REQUIRED, 2.2: REQUIRED, 2.3: REQUIRED
----------------------------------------
YAML.dump doesn't quote string "019" but it is recognized as float using Core Schema tag resolution option of YAML 1.2 specification.
Therefore, SnakeYAML (Java) recognizes a string "019" serialized by Ruby's YAML as float 19.0 unexpectedly.

YAML.dump works as following:

~~~
irb(main):002:0> require 'yaml'
=> true
irb(main):003:0> puts YAML.dump({'a' => '017'})
---
a: '017'
=> nil
irb(main):004:0> puts YAML.dump({'a' => '019'})
---
a: 019
=> nil
~~~

This is valid behavior as a YAML 1.1 implementation.
However, YAML 1.2 defines a new optional mechanism for resolving types implicitly. With this new option named Core Schema, type of 019 is resolved as tag:yaml.org,2002:float.
Here is the specification: http://www.yaml.org/spec/1.2/spec.html#id2805071

~~~
irb(main):002:0> /[-+]?(\.[0-9]+|[0-9]+(\.[0-9]*)?)([eE][-+]?[0-9]+)?/ =~ '019'
=> 0
~~~

I think it's better to quote 019 as '019' to avoid unexpected results when YAML is read by YAML 1.2 Core Schema implementation.

Related: a rejected pull-request to SnakeYAML
https://bitbucket.org/asomov/snakeyaml/pull-requests/4/fix-implicit-resolver-of-float-type-so/diff



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