Kernel#` and Kernel#system didn't correctly glob when using ruby

Recall the discussion in JRUBY-5873; this happens because there is no globbing (which is done by the shell) when JRuby takes a shortcut inside back ticks. You can either be more explicit in listing the files, or spawn a new process with -J-Djruby.launch.inproc=false.

Does this make sense?

True, but since JRuby is already looking at the command before passing to shell, isn't it good if it can also expand the glob, just as other rubies..? Personally, I don't want to have switches in my code for JRuby.

But maybe you're right, passing -J-Djruby.launch.inproc=true should solve all this. Or is it possible to emit some suggestion, just like asking user to install jruby-openssl, or like asking user to add -X+O to turn on ObjectSpace. It's helpful and people might not wonder if it's a bug or not anymore.

Thanks for considering.

I do not doubt that -J-Djruby.launch.inproc=false gives you a more MRI-compatible behavior. But this is often (think running Specs, unit tests, etc.) too high a price to pay, since spinning up JVM is quite expensive. So the default is to be incompatible.

JRuby's algorithm to make the decision on whether or not to run the "child" process inside or not is very limited to say the least. It means that it doesn't do any globbing, which can be quite hairy; for example,

$ ls bench/bench_{io,loop,method}_[^to,for]*.rb
bench/bench_io_gets.rb			bench/bench_loop_versus_while.rb
bench/bench_io_sysread.rb		bench/bench_method_missing.rb

If there is an easy way to account for all glob patterns, then it might be worth pursuing. But for now, it doesn't seem worthwhile.

Perhaps we could warn if we see *, ?, braces or square brackets. Is there any other special character in globbing?

A warning is fine for me.

As for when to warn, is it possible to emit the warning whenever JRuby tries to reuse the existing JVM, no matter if the user wants glob or not? Since this is already an incompatibility, it would be good if users from other rubies could be aware of this special case in JRuby.

Thanks!

On the other hand, this is off topic, but I hope people can start writing tests without using Rake to invoke shells. I changed all my tests running inside the process running Rake instead of using shells. I guess this is really what we want, so that we can pass Ruby options as normal.

I'm not sure if we should warn on all occasions. I think it would be too noisy.

I put in the warning to the master. https://github.com/jruby/jruby/commit/2ebb5799eff5d7d0dddf88cbfda9130c09f0f2b0

Testing habits are hard to change, unfortunately.

Resolving.

Thank you!