Parse.load with an IO/File which has a non-YAML allowed encoding will just

set the encoding to UTF-8 and hope for the best.  This appears to be how
libyaml works.

This issue was noticed in yaml/store because it extends pstore which will
create an IO in read_only mode as:

```ruby
RD_ACCESS = {mode: IO::RDONLY | IO::BINARY, encoding: Encoding::ASCII_8BIT}
```

The data in the test case I was debugging was in fact UTF-8 data and MRI was
happy to take this 8bit IO and pretend it is UTF-8.  Form-fitting ftw.

1 files changed, 12 insertions, 0 deletions

diff --git a/test/psych/test_encoding.rb b/test/psych/test_encoding.rb
index a4f9f03..01ebe25 100644
--- a/test/psych/test_encoding.rb
+++ b/test/psych/test_encoding.rb
@@ -106,6 +106,18 @@ module Psych
       }
     end
 
+    def test_io_utf8_read_as_binary
+      Tempfile.create(['utf8', 'yml']) {|t|
+        t.binmode
+        t.write '--- こんにちは！'.encode('UTF-8')
+        t.close
+
+        File.open(t.path, 'rb', :encoding => 'ascii-8bit') do |f|
+          assert_equal "こんにちは！", Psych.load(f)
+        end
+      }
+    end    
+
     def test_emit_alias
       @emitter.start_stream Psych::Parser::UTF8
       @emitter.start_document [], [], true