Now that we have gems:unpack and gems:build allowing for integration of

100% of your gems into vendor/ it would be nice to have the ability to
automatically unpack the full dependency tree of your specified gems.

This patch adds the rake task gems:unpack:dependencies to do this.

Usage:

gems:unpack:dependencies          # unpack all dependencies
gems:unpack:dependencies GEM=foo  # unpack all dependencies for gem foo

railties/lib/rails/gem_dependency.rb

@@ -8,11 +8,17 @@ module Rails
 
     def initialize(name, options = {})
       require 'rubygems' unless Object.const_defined?(:Gem)
-      @name     = name.to_s
-      if options[:version]
+
+      if options[:requirement]
+        @requirement = options[:requirement]
+      elsif options[:version]
         @requirement = Gem::Requirement.create(options[:version])
-        @version     = @requirement.instance_variable_get("@requirements").first.last
+      else
+        raise ArgumentError.new('Must pass either :version or :requirement')
       end
+
+      @version     = @requirement.instance_variable_get("@requirements").first.last if @requirement
+      @name     = name.to_s
       @lib      = options[:lib]
       @source   = options[:source]
       @loaded   = @frozen = @load_paths_added = false
@@ -35,6 +41,14 @@ module Rails
       puts $!.to_s
     end
     
+    def dependencies
+      all_dependencies = specification.dependencies.map do |dependency|
+        GemDependency.new(dependency.name, :requirement => dependency.version_requirements)
+      end
+      all_dependencies += all_dependencies.map(&:dependencies).flatten
+      all_dependencies.uniq
+    end
+    
     def gem_dir(base_directory)
       File.join(base_directory, specification.full_name)
     end
@@ -64,10 +78,6 @@ module Rails
       Gem::GemRunner.new.run(install_command)
     end
     
-    def specification
-      @spec ||= Gem.source_index.search(Gem::Dependency.new(@name, @requirement)).sort_by { |s| s.version }.last
-    end
-
     def unpack_to(directory)
       FileUtils.mkdir_p directory
       Dir.chdir directory do
@@ -83,6 +93,16 @@ module Rails
       end
     end
 
+    def ==(other)
+      self.name == other.name && self.requirement == other.requirement
+    end
+
+private ###################################################################
+
+    def specification
+      @spec ||= Gem.source_index.search(Gem::Dependency.new(@name, @requirement)).sort_by { |s| s.version }.last
+    end
+
     def install_command
       cmd = %w(install) << @name
       cmd << "--version" << "#{@requirement.to_s}" if @requirement

railties/lib/tasks/gems.rake

@@ -39,4 +39,20 @@ namespace :gems do
       gem.unpack_to(File.join(RAILS_ROOT, 'vendor', 'gems')) if gem.loaded?
     end
   end
+  
+  namespace :unpack do
+    desc "Unpacks the specified gems and its dependencies into vendor/gems"
+    task :dependencies => :unpack do
+      require 'rubygems'
+      require 'rubygems/gem_runner'
+      Rails.configuration.gems.each do |gem|
+        next unless ENV['GEM'].blank? || ENV['GEM'] == gem.name
+        gem.dependencies.each do |dependency|
+          dependency.add_load_paths # double check that we have not already unpacked
+          next if dependency.frozen?
+          dependency.unpack_to(File.join(RAILS_ROOT, 'vendor', 'gems'))
+        end
+      end
+    end
+  end
 end