[Rubygems-developers] Gem autoloading problems

Donavan Pantke avatar at spellboundnet.com
Wed Apr 16 22:05:01 EDT 2008

So, we were messing around with Passenger for rails recently, and ran into 
some behavior that I think needs to be addressed, but I'm not sure how.

Gems, I think as of 1.0, automatically activates a gem's dependencies based on 
what its spec says. However, the gem itself has no control over this. This 
makes life really hard on systems that need specific handling. In the case of 
Passenger, the rails gem is loaded based on the version requested, and more 
than one can be loaded (the process forks before rails gets loaded, allowing 
multiple versions to be in memory and accessible). However, if the gemspec 
has rails in it, activating passenger means that rails automatically gets 
activated, and so any further rails activation with a different version 
fails. However, the gemspec is entirely correct in that it needs 
_some_version of rails, but it really needs to do the activating of the 
dependency itself.

The first question I have is, what mechanism can be made available to avert 
activating a dependent gem until the gem actually needs it?

The next, bigger question IMO is, what should be the default? I can think of 
code paths where loading by default would make it really difficult for people 
needing deferred loading, but I may be overestimating the scope. 

So what do you guys think? I can help to write up the code, but I wanted input 
on what to write. :)


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