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Created March 17, 2012 18:27
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Developing with dependent local gem repositories

When developing an application where you have split out shared functionality to multiple dependent gem repositories can get cumbersome when you

  • need to edit the Gemfile in order to swap local :path sources with :git or just plain Rubygems sources,
  • then forget to bundle update,
  • wonder why your git repository is dirty and it's just the modified Gemfile and Gemfile.lock,
  • accidentally commit the Gemfile.lock with local :path sources bundled etc. etc.

So what about this strategy:

A. Create a file .Gemfile.local containing:

base = '..' # might need to tweak this according to your directory layout

B. Change your actual Gemfile to something like this:

base ||= 'git://'
type = base[0, 2] == '..' ? :path : :git

gem 'foo', type => "#{base}/foo"
gem 'bar', type => "#{base}/bar"

C. Add the .Gemfile* to your .gitignore file so that other developers can create their own .Gemfile.local and tweak the base path to their directory layout.

D. Switch between both Gemfiles using export BUNDLE_GEMFILE=.Gemfile.local and export BUNDLE_GEMFILE=Gemfile

Voila. It is acceptably easy to switch between using local vs remote gem sources with just a few lines of code. Switching to local/remote gem sources won't dirty the git repository.

Obviously, if you've changed your Gemfile then you still need to remember to switch to remote gem sources and bundle update once you're done and want to commit/push changes (where you don't gitignore the Gemfile.lock).

What do you think?

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KL-7 commented Mar 17, 2012

There are some issues and pull requests for bundler related to this topic. Like this one. Hopefully, we'll get some built-in solution for that in the future. For now, on our work project, we check env variable in the Gemfile to switch between gem from github and from local directory.

Recently I spotted another nice solution in travis-worker Gemfile. Should work great for some cases, but I wish I could extract this method into some other gem. As it's used right in the Gemfile it makes some problems. Is there any way to extend Gemfile DSL without using forked version of bundler (that is obviously not a solution)?

@josevalim, idea with pre-commit hook is pretty cool, thanks.

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wow, thanks for the feedback, people.

@josevalim having both options combined with a env variable could work. but then again devs often times have their local sources in different places which is hard to solve with having everything in one Gemfile and committed.

I love the pre-commit hook idea!

@jonleighton same, the priority source feature would need to allow to set different paths for different devs (and ideally per gem, too, which is one drawback of my solution above ... all the repositories need to be subdirectories of one dir).

@KL-7 yeah, the solution in travis-worker requires to add/delete symlinks in order to switch sources.

Thinking about it I guess if Bundler supported some sort of plugins (like Rubygems does) we'd be good to go. Everybody could monkeypatch away and experiment with different concepts before anything gets added to Bundler itself.

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josevalim commented Mar 19, 2012 via email

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@josevalim Awesome work, dude! That'll come in really handy. But I was wondering if Bundler should limit a local override option to git-only dependencies. The problem of gems in development remains for rubygems-dependencies. I opened an issue, mainly for discussion at first: rubygems/bundler#1802.

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josevalim commented Mar 28, 2012 via email

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