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Finally I understood Bundler and Gemfile!
Avoiding the “it works (only) on my machine” effect is a critical goal of DevOps. And adequately using a system for managing the dependencies of your application is a relevant part of it!
My background in management dependency tools is mostly with Maven for Java and Pip for Python. Once in a while
, I have also done some stuff in Ruby, and I confess I had a hard time using Bundler since I did not understand well some details like: why having Gemfile.lock; whether Gemfile.lock should be versioned or not; why using bundle exec to execute commands; and (since I did not use bundle exec) how different applications coexist in the same machine using different library versions.
So, by making this site, finally I found the bits of documentation that elucidated things to me:
bundle-install - Install the dependencies specified in your Gemfile
Install the gems specified in your Gemfile. If this is the first time you run bundle install (and a Gemfile.lock does not exist), Bundler will fetch all remote sources, resolve dependencies and install all needed gems.
If a Gemfile.lock does exist, and you have not updated your Gemfile, Bundler will fetch all remote sources, but use the dependencies specified in the Gemfile.lock instead of resolving dependencies.
If a Gemfile.lock does exist, and you have updated your Gemfile, Bundler will use the dependencies in the Gemfile.lock for all gems that you did not update, but will re-resolve the dependencies of gems that you did update.
Original docs on bundle install
Obs: therefore, I conclude the Gemfile.lock must be versioned so that every developer use the same library versions.
bundle-exec - Execute a command in the context of the bundle
This command executes the command, making all gems specified in the Gemfile available to require in Ruby programs.