Different Encoding behavior from all other Rubies #2580
Description
See rspec/rspec-support#172 (comment) for origin of this issue.
In brief, on all other Rubies, "\x80".force_encoding("US-ASCII").chars.map{|char| char.valid_encoding? ? char : "?" }.join.encode("UTF-8") returns ?, but JRUBY returns \x80
LANG=en_US.UTF-8 LC_ALL=en_US.UTF-8 \
rvm ruby-1.9.2-p330,ruby-1.9.3-p551,ruby-2.0.0-p598,ruby-2.1.5,ruby-2.2.0,jruby-1.7.18,rbx-2.2.2 do \
ruby -e 'p [RUBY_VERSION, RUBY_ENGINE, Encoding.default_external, __ENCODING__] << "\x80".force_encoding("US-ASCII").chars.map{|char| char.valid_encoding? ? char : "?" }.join.encode("UTF-8")'
for version in 1.9 2.0; do \
export JRUBY_OPTS="-Xcompat.version=${version}" ; \
LANG=en_US.UTF-8 LC_ALL=en_US.UTF-8 \
rvm jruby-1.7.18 do \
ruby -e 'p [RUBY_VERSION, RUBY_ENGINE, Encoding.default_external, __ENCODING__] << "\x80".force_encoding("US-ASCII").chars.map{|char| char.valid_encoding? ? char : "?" }.join.encode("UTF-8")';
done["1.9.2", "ruby", #<Encoding:UTF-8>, #<Encoding:UTF-8>, "?"]
["1.9.3", "ruby", #<Encoding:UTF-8>, #<Encoding:UTF-8>, "?"]
["2.0.0", "ruby", #<Encoding:UTF-8>, #<Encoding:UTF-8>, "?"]
["2.1.5", "ruby", #<Encoding:UTF-8>, #<Encoding:UTF-8>, "?"]
["2.2.0", "ruby", #<Encoding:UTF-8>, #<Encoding:UTF-8>, "?"]
["1.9.3", "jruby", #<Encoding:UTF-8>, #<Encoding:UTF-8>, "\x80"]
["2.1.0", "rbx", #<Encoding:UTF-8>, #<Encoding:UTF-8>, "?"]
["1.9.3", "jruby", #<Encoding:UTF-8>, #<Encoding:UTF-8>, "\x80"]
["2.0.0", "jruby", #<Encoding:UTF-8>, #<Encoding:UTF-8>, "\x80"]