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diff --git a/jni/ruby/lib/rubygems/dependency_list.rb b/jni/ruby/lib/rubygems/dependency_list.rb
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+++ b/jni/ruby/lib/rubygems/dependency_list.rb
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+#--
+# Copyright 2006 by Chad Fowler, Rich Kilmer, Jim Weirich and others.
+# All rights reserved.
+# See LICENSE.txt for permissions.
+#++
+
+require 'tsort'
+require 'rubygems/deprecate'
+
+##
+# Gem::DependencyList is used for installing and uninstalling gems in the
+# correct order to avoid conflicts.
+#--
+# TODO: It appears that all but topo-sort functionality is being duplicated
+# (or is planned to be duplicated) elsewhere in rubygems.  Is the majority of
+# this class necessary anymore?  Especially #ok?, #why_not_ok?
+
+class Gem::DependencyList
+  attr_reader :specs
+
+  include Enumerable
+  include TSort
+
+  ##
+  # Allows enabling/disabling use of development dependencies
+
+  attr_accessor :development
+
+  ##
+  # Creates a DependencyList from the current specs.
+
+  def self.from_specs
+    list = new
+    list.add(*Gem::Specification.to_a)
+    list
+  end
+
+  ##
+  # Creates a new DependencyList.  If +development+ is true, development
+  # dependencies will be included.
+
+  def initialize development = false
+    @specs = []
+
+    @development = development
+  end
+
+  ##
+  # Adds +gemspecs+ to the dependency list.
+
+  def add(*gemspecs)
+    @specs.concat gemspecs
+  end
+
+  def clear
+    @specs.clear
+  end
+
+  ##
+  # Return a list of the gem specifications in the dependency list, sorted in
+  # order so that no gemspec in the list depends on a gemspec earlier in the
+  # list.
+  #
+  # This is useful when removing gems from a set of installed gems.  By
+  # removing them in the returned order, you don't get into as many dependency
+  # issues.
+  #
+  # If there are circular dependencies (yuck!), then gems will be returned in
+  # order until only the circular dependents and anything they reference are
+  # left.  Then arbitrary gemspecs will be returned until the circular
+  # dependency is broken, after which gems will be returned in dependency
+  # order again.
+
+  def dependency_order
+    sorted = strongly_connected_components.flatten
+
+    result = []
+    seen = {}
+
+    sorted.each do |spec|
+      if index = seen[spec.name] then
+        if result[index].version < spec.version then
+          result[index] = spec
+        end
+      else
+        seen[spec.name] = result.length
+        result << spec
+      end
+    end
+
+    result.reverse
+  end
+
+  ##
+  # Iterator over dependency_order
+
+  def each(&block)
+    dependency_order.each(&block)
+  end
+
+  def find_name(full_name)
+    @specs.find { |spec| spec.full_name == full_name }
+  end
+
+  def inspect # :nodoc:
+    "#<%s:0x%x %p>" % [self.class, object_id, map { |s| s.full_name }]
+  end
+
+  ##
+  # Are all the dependencies in the list satisfied?
+
+  def ok?
+    why_not_ok?(:quick).empty?
+  end
+
+  def why_not_ok? quick = false
+    unsatisfied = Hash.new { |h,k| h[k] = [] }
+    each do |spec|
+      spec.runtime_dependencies.each do |dep|
+        inst = Gem::Specification.any? { |installed_spec|
+          dep.name == installed_spec.name and
+            dep.requirement.satisfied_by? installed_spec.version
+        }
+
+        unless inst or @specs.find { |s| s.satisfies_requirement? dep } then
+          unsatisfied[spec.name] << dep
+          return unsatisfied if quick
+        end
+      end
+    end
+
+    unsatisfied
+  end
+
+  ##
+  # Is is ok to remove a gemspec from the dependency list?
+  #
+  # If removing the gemspec creates breaks a currently ok dependency, then it
+  # is NOT ok to remove the gemspec.
+
+  def ok_to_remove?(full_name, check_dev=true)
+    gem_to_remove = find_name full_name
+
+    siblings = @specs.find_all { |s|
+      s.name == gem_to_remove.name &&
+        s.full_name != gem_to_remove.full_name
+    }
+
+    deps = []
+
+    @specs.each do |spec|
+      check = check_dev ? spec.dependencies : spec.runtime_dependencies
+
+      check.each do |dep|
+        deps << dep if gem_to_remove.satisfies_requirement?(dep)
+      end
+    end
+
+    deps.all? { |dep|
+      siblings.any? { |s|
+        s.satisfies_requirement? dep
+      }
+    }
+  end
+
+  ##
+  # Remove everything in the DependencyList that matches but doesn't
+  # satisfy items in +dependencies+ (a hash of gem names to arrays of
+  # dependencies).
+
+  def remove_specs_unsatisfied_by dependencies
+    specs.reject! { |spec|
+      dep = dependencies[spec.name]
+      dep and not dep.requirement.satisfied_by? spec.version
+    }
+  end
+
+  ##
+  # Removes the gemspec matching +full_name+ from the dependency list
+
+  def remove_by_name(full_name)
+    @specs.delete_if { |spec| spec.full_name == full_name }
+  end
+
+  ##
+  # Return a hash of predecessors.  <tt>result[spec]</tt> is an Array of
+  # gemspecs that have a dependency satisfied by the named gemspec.
+
+  def spec_predecessors
+    result = Hash.new { |h,k| h[k] = [] }
+
+    specs = @specs.sort.reverse
+
+    specs.each do |spec|
+      specs.each do |other|
+        next if spec == other
+
+        other.dependencies.each do |dep|
+          if spec.satisfies_requirement? dep then
+            result[spec] << other
+          end
+        end
+      end
+    end
+
+    result
+  end
+
+  def tsort_each_node(&block)
+    @specs.each(&block)
+  end
+
+  def tsort_each_child(node)
+    specs = @specs.sort.reverse
+
+    dependencies = node.runtime_dependencies
+    dependencies.push(*node.development_dependencies) if @development
+
+    dependencies.each do |dep|
+      specs.each do |spec|
+        if spec.satisfies_requirement? dep then
+          yield spec
+          break
+        end
+      end
+    end
+  end
+
+  private
+
+  ##
+  # Count the number of gemspecs in the list +specs+ that are not in
+  # +ignored+.
+
+  def active_count(specs, ignored)
+    specs.count { |spec| ignored[spec.full_name].nil? }
+  end
+
+end
+