Support YAML 1.2 Core Schema. Addressed https://bugs.ruby-lang.org/issues/11988issue-11988

2 files changed, 7 insertions, 1 deletions

diff --git a/lib/psych/visitors/yaml_tree.rb b/lib/psych/visitors/yaml_tree.rb
index 6ad30d2..cf2d06f 100644
--- a/lib/psych/visitors/yaml_tree.rb
+++ b/lib/psych/visitors/yaml_tree.rb
@@ -330,7 +330,7 @@ module Psych
           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
           style = Nodes::Scalar::SINGLE_QUOTED
         end
 
diff --git a/test/psych/visitors/test_yaml_tree.rb b/test/psych/visitors/test_yaml_tree.rb
index 40702bc..b7116a5 100644
--- a/test/psych/visitors/test_yaml_tree.rb
+++ b/test/psych/visitors/test_yaml_tree.rb
@@ -155,6 +155,12 @@ module Psych
         assert_equal(-1, Psych.load(Psych.dump(-1 / 0.0)).infinite?)
       end
 
+      def test_string
+        assert_match(/'017'/, Psych.dump({'a' => '017'}))
+        assert_match(/'019'/, Psych.dump({'a' => '019'}))
+        assert_match(/'01818'/, Psych.dump({'a' => '01818'}))
+      end
+
       # http://yaml.org/type/null.html
       def test_nil
         assert_cycle nil