io.c: conversion from bom encoding

* io.c (rb_io_ext_int_to_encs, parse_mode_enc): bom-prefixed name is
  not a real encoding name, just a fallback.  so the proper conversion
  should take place even if if the internal encoding is equal to the
  bom-prefixed name, unless actual encoding is equal to the internal
  encoding.  [ruby-core:54563] [Bug #8323]
* io.c (io_set_encoding_by_bom): reset extenal encoding if no BOM
  found.  [ruby-core:54569]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40462 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 23 insertions, 1 deletions

diff --git a/test/ruby/test_io_m17n.rb b/test/ruby/test_io_m17n.rb
index 45ae75c6aa..ec2086186c 100644
--- a/test/ruby/test_io_m17n.rb
+++ b/test/ruby/test_io_m17n.rb
@@ -1997,6 +1997,7 @@ EOT
   def test_strip_bom
     with_tmpdir {
       text = "\uFEFFa"
+      stripped = "a"
       %w/UTF-8 UTF-16BE UTF-16LE UTF-32BE UTF-32LE/.each do |name|
         path = '%s-bom.txt' % name
         content = text.encode(name)
@@ -2004,11 +2005,32 @@ EOT
         result = File.read(path, mode: 'rb:BOM|UTF-8')
         assert_equal(content[1].force_encoding("ascii-8bit"),
                      result.force_encoding("ascii-8bit"))
+        result = File.read(path, mode: 'rb:BOM|UTF-8:UTF-8')
+        assert_equal(Encoding::UTF_8, result.encoding)
+        assert_equal(stripped, result)
       end
 
       bug3407 = '[ruby-core:30641]'
-      result = File.read('UTF-8-bom.txt', encoding: 'BOM|UTF-8')
+      path = 'UTF-8-bom.txt'
+      result = File.read(path, encoding: 'BOM|UTF-8')
       assert_equal("a", result.force_encoding("ascii-8bit"), bug3407)
+
+      bug8323 = '[ruby-core:54563] [Bug #8323]'
+      expected = "a\xff".force_encoding("utf-8")
+      open(path, 'ab') {|f| f.write("\xff")}
+      result = File.read(path, encoding: 'BOM|UTF-8')
+      assert_not_predicate(result, :valid_encoding?, bug8323)
+      assert_equal(expected, result, bug8323)
+      result = File.read(path, encoding: 'BOM|UTF-8:UTF-8')
+      assert_not_predicate(result, :valid_encoding?, bug8323)
+      assert_equal(expected, result, bug8323)
+
+      path = 'ascii.txt'
+      generate_file(path, stripped)
+      result = File.read(path, encoding: 'BOM|UTF-8')
+      assert_equal(stripped, result, bug8323)
+      result = File.read(path, encoding: 'BOM|UTF-8:UTF-8')
+      assert_equal(stripped, result, bug8323)
     }
   end