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.

2 files changed, 19 insertions, 0 deletions

diff --git a/ext/java/PsychParser.java b/ext/java/PsychParser.java
index b3e747e..f5b6faf 100644
--- a/ext/java/PsychParser.java
+++ b/ext/java/PsychParser.java
@@ -33,6 +33,8 @@ import java.nio.charset.Charset;
 import java.util.Map;
 
 import org.jcodings.Encoding;
+import org.jcodings.specific.UTF16BEEncoding;
+import org.jcodings.specific.UTF16LEEncoding;
 import org.jcodings.specific.UTF8Encoding;
 import org.jcodings.unicode.UnicodeEncoding;
 import org.jruby.Ruby;
@@ -162,6 +164,11 @@ public class PsychParser extends RubyObject {
             if (yaml instanceof RubyIO) {
                 Encoding enc = ((RubyIO) yaml).getReadEncoding();
                 charset = enc.getCharset();
+
+                // libyaml treats non-utf encodings as utf-8 and hopes for the best.
+                if (!(enc instanceof UTF8Encoding)  && !(enc instanceof UTF16LEEncoding) && !(enc instanceof UTF16BEEncoding)) {
+                    charset = UTF8Encoding.INSTANCE.getCharset();
+                }
             }
             if (charset == null) {
                 // If we can't get it from the IO or it doesn't have a charset, fall back on UTF-8
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