I just came to move some ruby scripts onto my mac mini, and to do so I needed to install a couple of gems. Now I realised I hadn’t installed or updated rubygems on the machine for a while, so I figured it was best to update gem before installing the gems I wanted. Easier said than done.

At some point in the past I had added http://gems.datamapper.org as a source to rubygems. Since then the datamapper project has discontinued using this gem source to serve up gems, so I was getting the following output:

mm:daemons caius$ sudo gem update --system
Updating installed gems
Bulk updating Gem source index for: http://gems.rubyforge.org/
ERROR:  While executing gem ... (Gem::RemoteSourceException)
    HTTP Response 404 fetching http://gems.datamapper.org/yaml

Eeek! I can’t update because the source no longer exists. So I figured I’d remove the source before updating, that should work right? Wrong. It updates the sources before removing the source from the config it would appear.

mm:daemons caius$ sudo gem sources
** CURRENT SOURCES ***

http://gems.rubyforge.org
http://gems.datamapper.org

mm:daemons caius$ sudo gem sources -r http://gems.datamapper.org
Bulk updating Gem source index for: http://gems.rubyforge.org/
ERROR:  While executing gem ... (Gem::RemoteSourceException)
    HTTP Response 404 fetching http://gems.datamapper.org/yaml

Oh balls. So how do I remove the source without updating it first. I need to update it to remove it, but to remove it I need to update from it. Gotta love catch 22s!

I remembered that gem install has an option not to update sources, --no-update-sources. So I figured thats gotta work when removing a source as well, but it doesn’t.

mm:daemons caius$ sudo gem sources -r http://gems.datamapper.org --no-update-sources
ERROR:  While executing gem ... (OptionParser::InvalidOption)
    invalid option: --no-update-sources

Oh crap. Now what do I do? Take my usual tactic and google for a hint of course! I’d considered trying to find where the gem config was and remove the source by hand, but I figured that wouldn’t be that simple. After hitting a couple of sites that weren’t relevant I ended up on the edge of complexity where he mentions the command nano ~/.gemrc. Which made me wonder if that file contains the sources.

mm:daemons caius$ cat ~/.gemrc
--- 
:update_sources: true
:verbose: true
:bulk_threshold: 1000
:sources: 
- http://gems.rubyforge.org
- http://gems.datamapper.org
:backtrace: false
:benchmark: false

All I needed to do was remove the - http://gems.datamapper.org line and poof, gem was working again. One quick gem update --system later and I was upgraded from gem 1.1.1 to 1.3.1 and installing the gems I needed.