Set external encoding correctly for File.open('f', FILE::BINARY) on Windows

Previously, the external encoding was only set correctly for
File::BINARY if keyword arguments were provided.  This copies
the logic for the keyword arguments case to the no keyword
arguments case.  Possibly it should be refactored into a
separate function.

Fixes [Bug #16737]

1 files changed, 12 insertions, 0 deletions

diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index a6df5c8b08..a49fd0130e 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -3630,15 +3630,27 @@ __END__
   end
 
   def test_open_flag_binary
+    binary_enc = Encoding.find("BINARY")
     make_tempfile do |t|
       open(t.path, File::RDONLY, flags: File::BINARY) do |f|
         assert_equal true, f.binmode?
+        assert_equal binary_enc, f.external_encoding
       end
       open(t.path, 'r', flags: File::BINARY) do |f|
         assert_equal true, f.binmode?
+        assert_equal binary_enc, f.external_encoding
       end
       open(t.path, mode: 'r', flags: File::BINARY) do |f|
         assert_equal true, f.binmode?
+        assert_equal binary_enc, f.external_encoding
+      end
+      open(t.path, File::RDONLY|File::BINARY) do |f|
+        assert_equal true, f.binmode?
+        assert_equal binary_enc, f.external_encoding
+      end
+      open(t.path, File::RDONLY|File::BINARY, autoclose: true) do |f|
+        assert_equal true, f.binmode?
+        assert_equal binary_enc, f.external_encoding
       end
     end
   end if File::BINARY != 0