missing config.gem

Rails::GemDependency#load prevents missing gems from aborting
application initialization:

   fxn@feynman:~/tmp/test_gem$ script/runner 'p 1'
   These gems that this application depends on are missing:
    - foo
   Run "rake gems:install" to install them.

Which is the rationale? Why would you want the initialization to go on
in spite of missing gems?

Ah, let me add that application initializers and other bits are
skipped altogether:

    def load_application_initializers
      if @gems_dependencies_loaded

so the application is definitely up in a (generally) broken state.

But there's such an clear care with those rescues and flags that I
guess there's going to be a reason for the current implementation.

This issue was raised before: http://groups.google.com/group/rubyonrails-core/browse_thread/thread/bd1ea7763627ed0d

Are your questions answered in that thread?

Hey thank you Mislav I missed that thread.

It is not clear to me that the rationale is explained there, but at
least I see there are people that have a notion of "optional
dependency" in which this behaviour might make sense for them.

I am for sure +1 on failing hard and handling your occasional optional
library with Ruby code anyway.

+1 for failing hard. If your application is smart enough to fall back
on an alternative behavior, rescue the exception and continue.

If the optional gem is common, why not a config.optional_gem method? Covers all bases explicitly and succinctly.

This was discussed in a recent thread. Rubygems already provides a
way to flag development gems. Aside from that, any determiniation of
"optional" is developer-, platform- or environment- specific, and is
best handled with custom code in the environment file(s). In any of
these cases, you would need some custom code anyway to determine
whether the non-development "optional" dependency is actually required
or not (inclusion in a specific environment file rather than
environment.rb, platform check, env var check, etc). So, if you need
custom code anyway, just write your own conditional to not even
execute the optional config.gem call. No need for a separate method.

-- Chad