[Rubygems-developers] env shebang always for JRuby

Charles Oliver Nutter charles.nutter at sun.com
Tue Apr 29 19:46:28 EDT 2008

First I'll say this isn't really related to the shebang thing. The env 
shebang hardcoding "/usr/bin/env ruby" would affect MRI too if you had 
an sh script not named 'ruby' you wanted to use as your launcher. That's 
essentially the case here; the 'jruby' command is a bash script that 
launches a JVM running JRuby. So that should be fixed to use the 
*actual* command name instead.

And the fact that we need env-shebangs by default is unrelated as 
well...it all comes back to the 'jruby' command being a bash script.

Second, I'll respond to a couple of your points.

Donavan Pantke wrote:
> First, I want to stress that there should only be one gem repo on a system. 
> RubyGems is platform-agnostic and handles selecting code based on interpreter 
> platform well. Having multiple system-wide gem repositores is asking for 
> trouble, since they all have to share a single PATH, and this problem is what 
> led to "gem" vs. "jgem". The easiest way to get rid of strange PATH problems 
> is to have one RubyGems managing it.

I think it should be an option that you have one repo, but I prefer to 
keep them separate myself. It certainly shouldn't be the default, since 
lots and lots of people install and use JRuby as their username, 
sometimes with a couple installs...and it ships with a couple IDEs, 
which package it in a subdir. Some people want to use a shared repo, 
some don't.

> So how can RubyGems select between several interpreters? We'll need a couple 
> of things to make this happen:
> - A way to determine the default interpreter on the system.
> This is easy to do on POSIX (symlink!), not so easy in Windows. Luis, do you 
> have any thoughts on this? Remember, we don't really care what interpreter is 
> called by "gem", so long as "gem" will run!

It would *seriously* suck if the only way to get rubygems to choose 
JRuby was by using a symlink...and the 'jruby' command isn't an 
executable, so gems installed without shebangs would not work wen you 
switched from ruby to jruby.

> - An interpreter-independent GEM_HOME. We need to statically define where gems 
> live so we gain platform/interpreter independence.

If you like, you can do that now and have JRuby access an existing 
GEM_HOME. I'm not sure people do it though.

> - A way for a gem to specify what interpreter has to be used.

This would definitely be nice to have in the gem metadata, since there's 
conceivably going to be five implementations to choose from that might 
all have their own extension mechanisms (ruby 1.8/1.9, jruby, rubinius, 
macruby [ObjC extensions?], ironruby).

> - A way for the user to specify an alternate interpreter at install time. 
> (Maybe at execution-time, too?)

Maybe...starts to get a little cumbersome at that point though.

- Charlie

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