问题
At runtime, after bundler setup is complete, and groups are applied, what is the best way to programmatically check if a given gem_name is in the bundle?
By reading the source, I've discovered Bundler.definition, e.g.
gem_name = 'banana'
Bundler.definition.dependencies.map(&:name).include?(gem_name)
but unable to find documentation1, I don't know if this is the recommended usage.
Update: It looks like Bundler::Definition#dependencies returns all dependencies, irrespective of groups. As an alternative, I've discovered Bundler::Runtime#dependencies_for which takes groups as arguments.
Bundler.load.dependencies_for(:default, Rails.env).map(&:name).include?(gem_name)
However, it seems like a bad idea to duplicate the "group lists" at every call site. Ideally, I'd like a method in Bundler that doesn't require me to specify the current groups.
1 The bundler website and man page are focused on command-line usage. I have not found any documentation on the gem's public ruby API. Comments in the source are helpful, but focused on data types, etc.
回答1:
Bundler is used to set up the applications gems, so you can use the Gem API rather than Bundler:
Gem.loaded_specs.has_key? gem_name
Bundler will have set things up so that any gems in the bundle (in the appropriate groups) have been activated (so they will have entries in loaded_specs) and any other (non-bundle) gems will be prevented from being loaded.
来源：https://stackoverflow.com/questions/27510136/programmatically-check-if-gem-in-bundle