move RubyDate and joda-time into "extension" gem

[mkristian]

a brief look into the code looks like it is possible to move all the code which uses joda-time into a gem which we can use in the same manner as jruby-readline.

advantage:

• you can decide on the joda-time version via jar-dependencies or jbundler or manually. so your required java libraries can decide which joda-time version to use without fiddling with classpath of jruby itself (kind of difficult with rvm and rbenv)
• reversing classloader.delegate will not produce errors regarding joda-time since all joda classes used by jruby living inside jrubyclassloader

disadvantage:

• extra gem

this is just an attempt to improve usefulness of this classloader.delegate and improve the overall classloader setup. other places are

• Add xalan jars to fix issues with #1114 sparklemotion/nokogiri#1212 which still needs some code changes
• simplecov triggers load error when running coverage on jruby-9.0.0.0.pre1 #2587 - not sure what happens here, need to investigate and did not see the issue earlier

[nirvdrum]

Allowing arbitrary versions of joda to be used sounds like a bad idea. We can't make any guarantees about compatibility with versions other than the one we support and I'd hate to see our support policy broaden to whatever version of joda. If there's a classpath conflict, I suggest we shade joda and rename the package.

[mkristian]

joda classes are part of the jruby API so shading breaks any binary compatibility. and this is actually the reason why the idea will probably not work, you need joda to compile your code against jruby. but for info it is easy to use another version of joda with the jruby maven artifact, you might not even know that you are doing - or you ruby code uses a library depending on joda (via jbundler) and you just use the joda coming from jruby. I can tell the same story with snakeyaml and give you a gem which depends on an embedded snakeyaml but will "silently" not use the embedded jar. well with the psych gem in 9k.pre2 this is history and that is where the idea came from.

[kares]

with 9.2 only supporting Java 8 we could have been moving towards getting rid of joda-time.
of course due it being part of the API its not as simple.
am hoping providing Java 8 alternatives in the APIs such as RubyTime (and maybe doing deprecations).
anyway, I believe this issue is now pretty much defunct ...