merge revision(s) e86c1f6fc53433ef5c82ed2b7a4cc9a12c153e4c,f6539202c52a051a4e6946a318a1d9cd29002990: [Backport #1205]

	Work around issue transcoding issue with non-ASCII compatible
	 encodings and xml escaping

	When using a non-ASCII compatible source and destination encoding
	and xml escaping (the :xml option to String#encode), the resulting
	string was broken, as it used the correct non-ASCII compatible
	encoding, but contained data that was ASCII-compatible instead of
	compatible with the string's encoding.

	Work around this issue by detecting the case where both the
	source and destination encoding are non-ASCII compatible, and
	transcoding the source string from the non-ASCII compatible
	encoding to UTF-8. The xml escaping code will correctly handle
	the UTF-8 source string and the return the correctly encoded
	and escaped value.

	Fixes [Bug #12052]

	Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>
	---
	 test/ruby/test_transcode.rb | 19 +++++++++++++++++++
	 transcode.c                 |  6 ++++++
	 2 files changed, 25 insertions(+)

	=?UTF-8?q?-=20add=20regression=20tests=20for=20U+6E7F=20(?=
	 =?UTF-8?q?=E6=B9=BF)=20in=20ISO-2022-JP?=
	MIME-Version: 1.0
	Content-Type: text/plain; charset=UTF-8
	Content-Transfer-Encoding: 8bit

	  In ISO-2022-JP, the bytes use to code are the same as those for "<>".
	  This adds regression tests to make sure that these bytes, when representing
	  湿, are NOT　escaped with encode("ISO-2022-JP, xml: :text) or similar.
	  These are additional regression tests for #12052.
	---
	 test/ruby/test_transcode.rb | 3 +++
	 1 file changed, 3 insertions(+)

1 files changed, 22 insertions, 0 deletions

diff --git a/test/ruby/test_transcode.rb b/test/ruby/test_transcode.rb
index 04c8248697..c8b0034e06 100644
--- a/test/ruby/test_transcode.rb
+++ b/test/ruby/test_transcode.rb
@@ -126,6 +126,28 @@ class TestTranscode < Test::Unit::TestCase
     assert_equal("D\xFCrst".force_encoding('iso-8859-2'), "D\xFCrst".encode('iso-8859-2', 'iso-8859-1'))
   end
 
+  def test_encode_xml_multibyte
+    encodings = %w'UTF-8 UTF-16LE UTF-16BE UTF-32LE UTF-32BE'
+    encodings.each do |src_enc|
+      encodings.each do |dst_enc|
+        escaped = "<>".encode(src_enc).encode(dst_enc, :xml=>:text)
+        assert_equal("&lt;&gt;", escaped.encode('UTF-8'), "failed encoding #{src_enc} to #{dst_enc} with xml: :text")
+
+        escaped = '<">'.encode(src_enc).encode(dst_enc, :xml=>:attr)
+        assert_equal('"&lt;&quot;&gt;"', escaped.encode('UTF-8'), "failed encoding #{src_enc} to #{dst_enc} with xml: :attr")
+
+        escaped = "<>".encode(src_enc).force_encoding("UTF-8").encode(dst_enc, src_enc, :xml=>:text)
+        assert_equal("&lt;&gt;", escaped.encode('UTF-8'), "failed encoding #{src_enc} to #{dst_enc} with xml: :text")
+
+        escaped = '<">'.encode(src_enc).force_encoding("UTF-8").encode(dst_enc, src_enc, :xml=>:attr)
+        assert_equal('"&lt;&quot;&gt;"', escaped.encode('UTF-8'), "failed encoding #{src_enc} to #{dst_enc} with xml: :attr")
+      end
+    end
+    # regression test; U+6E7F (湿) uses the same bytes in ISO-2022-JP as "<>"
+    assert_equal(  "&lt;&gt;\u6E7F",   "<>\u6E7F".encode("ISO-2022-JP").encode("ISO-2022-JP", :xml=>:text).encode("UTF-8"))
+    assert_equal("\"&lt;&gt;\u6E7F\"", "<>\u6E7F".encode("ISO-2022-JP").encode("ISO-2022-JP", :xml=>:attr).encode("UTF-8"))
+  end
+
   def test_ascii_range
     encodings = [
       'US-ASCII', 'ASCII-8BIT',