Referencing a local gem in Gemfile

In a recent post, I discussed my new debugging technique of pulling down third party libraries. While having the code local to read and search is a win in and of itself, running the code can be even more helpful. Since this new practice is a habit I am still working to develop, I thought I would write down how to get it working. Hopefully, this reduces the friction for my future self.

What to do

Since our project is using Bundler, I was able to update the line where we add the gem in question to use the path option and point it to the (relative) path on my system:

# Gemfile
gem 'gem-im-debugging', path: '../gem-im-debugging'

Currently, I keep all repositories in the same directory. This enables me to use the relative path to the parent directory to find the local version of the gem I am debugging. Depending on where you copy the project, you may need to adjust your path.

Possible alternative

As I was trying to find the documentation to link to in this post, I also found this option:

bundle config local.GEM_NAME /path/to/local/git/repository

Below is the example from the docs getting it working for a local version of rack.

In your terminal set Bundler to use your local version of the gem:

bundle config local.rack ~/Work/git/rack

and then in your Gemfile, you can include the gem as though you are pulling it off of GitHub:

# Gemfile
gem 'rack', :github => 'rack/rack', :branch => 'master'

My initial impression is that this could achieve the same thing, but seems to take a bit more work.

My guess is this would be useful if you regularly work on a gem and want to have some test projects around. Being able to reference different branches from the test project itself could be useful. Also, based on the documentation it seems path will not compile C extensions, but git (and github?) will. If you are working with C extensions you may have to leverage this alternative method.

As I find more opportunities to work with gems locally, I may want to revisit this option (and learn how to turn it back off).