Merge https://github.com/rubygems/rubygems/commit/3f7d0352e84b29d4a2d4cd93b31e5ebdb5f79cc6

10 files changed, 433 insertions, 408 deletions

diff --git a/lib/bundler/definition.rb b/lib/bundler/definition.rb
index 09be2db68c..c1d865d049 100644
--- a/lib/bundler/definition.rb
+++ b/lib/bundler/definition.rb
@@ -736,30 +736,13 @@ module Bundler
 
     def metadata_dependencies
       @metadata_dependencies ||= begin
-        ruby_versions = ruby_version_requirements(@ruby_version)
         [
-          Dependency.new("Ruby\0", ruby_versions),
+          Dependency.new("Ruby\0", RubyVersion.system.gem_version),
           Dependency.new("RubyGems\0", Gem::VERSION),
         ]
       end
     end
 
-    def ruby_version_requirements(ruby_version)
-      return [] unless ruby_version
-      if ruby_version.patchlevel
-        [ruby_version.to_gem_version_with_patchlevel]
-      else
-        ruby_version.versions.map do |version|
-          requirement = Gem::Requirement.new(version)
-          if requirement.exact?
-            "~> #{version}.0"
-          else
-            requirement
-          end
-        end
-      end
-    end
-
     def expand_dependencies(dependencies, remote = false)
       deps = []
       dependencies.each do |dep|
diff --git a/lib/bundler/resolver.rb b/lib/bundler/resolver.rb
index be0751d9d2..433a5e53e1 100644
--- a/lib/bundler/resolver.rb
+++ b/lib/bundler/resolver.rb
@@ -312,29 +312,66 @@ module Bundler
 
       e = Molinillo::VersionConflict.new(conflicts, e.specification_provider) unless conflicts.empty?
 
-      solver_name = "Bundler"
-      possibility_type = "gem"
       e.message_with_trees(
-        :solver_name => solver_name,
-        :possibility_type => possibility_type,
-        :reduce_trees => lambda do |trees|
+        :full_message_for_conflict => lambda do |name, conflict|
+          o = if name.end_with?("\0")
+            String.new("Bundler found conflicting requirements for the #{name} version:")
+          else
+            String.new("Bundler could not find compatible versions for gem \"#{name}\":")
+          end
+          o << %(\n)
+          if conflict.locked_requirement
+            o << %(  In snapshot (#{name_for_locking_dependency_source}):\n)
+            o << %(    #{SharedHelpers.pretty_dependency(conflict.locked_requirement)}\n)
+            o << %(\n)
+          end
+          o << %(  In #{name_for_explicit_dependency_source}:\n)
+          trees = conflict.requirement_trees
+
           # called first, because we want to reduce the amount of work required to find maximal empty sets
           trees = trees.uniq {|t| t.flatten.map {|dep| [dep.name, dep.requirement] } }
 
           # bail out if tree size is too big for Array#combination to make any sense
-          return trees if trees.size > 15
-          maximal = 1.upto(trees.size).map do |size|
-            trees.map(&:last).flatten(1).combination(size).to_a
-          end.flatten(1).select do |deps|
-            Bundler::VersionRanges.empty?(*Bundler::VersionRanges.for_many(deps.map(&:requirement)))
-          end.min_by(&:size)
-
-          trees.reject! {|t| !maximal.include?(t.last) } if maximal
-
-          trees.sort_by {|t| t.reverse.map(&:name) }
-        end,
-        :printable_requirement => lambda {|req| SharedHelpers.pretty_dependency(req) },
-        :additional_message_for_conflict => lambda do |o, name, conflict|
+          if trees.size <= 15
+            maximal = 1.upto(trees.size).map do |size|
+              trees.map(&:last).flatten(1).combination(size).to_a
+            end.flatten(1).select do |deps|
+              Bundler::VersionRanges.empty?(*Bundler::VersionRanges.for_many(deps.map(&:requirement)))
+            end.min_by(&:size)
+
+            trees.reject! {|t| !maximal.include?(t.last) } if maximal
+
+            trees.sort_by! {|t| t.reverse.map(&:name) }
+          end
+
+          metadata_requirements = {}
+
+          o << trees.map do |tree|
+            t = "".dup
+            depth = 2
+
+            base_tree = tree.first
+            base_tree_name = base_tree.name
+
+            if base_tree_name.end_with?("\0")
+              metadata_requirements[base_tree_name] = base_tree
+              t = nil
+            else
+              tree.each do |req|
+                t << "  " * depth << SharedHelpers.pretty_dependency(req)
+                unless tree.last == req
+                  if spec = conflict.activated_by_name[req.name]
+                    t << %( was resolved to #{spec.version}, which)
+                  end
+                  t << %( depends on)
+                end
+                t << %(\n)
+                depth += 1
+              end
+            end
+            t
+          end.compact.join("\n")
+
           if name == "bundler"
             o << %(\n  Current Bundler version:\n    bundler (#{Bundler::VERSION}))
 
@@ -355,11 +392,13 @@ module Bundler
                 o << "Your bundle requires a different version of Bundler than the one you're running, and that version could not be found.\n"
               end
             end
+          elsif name.end_with?("\0")
+            o << %(\n  Current #{name} version:\n    #{SharedHelpers.pretty_dependency(metadata_requirements[name])}\n\n)
           elsif conflict.locked_requirement
             o << "\n"
             o << %(Running `bundle update` will rebuild your snapshot from scratch, using only\n)
             o << %(the gems in your Gemfile, which may resolve the conflict.\n)
-          elsif !conflict.existing && !name.end_with?("\0")
+          elsif !conflict.existing
             o << "\n"
 
             relevant_source = conflict.requirement.source || source_for(name)
@@ -372,14 +411,8 @@ module Bundler
 
             o << gem_not_found_message(name, conflict.requirement, relevant_source, extra_message)
           end
-        end,
-        :version_for_spec => lambda {|spec| spec.version },
-        :incompatible_version_message_for_conflict => lambda do |name, _conflict|
-          if name.end_with?("\0")
-            %(#{solver_name} found conflicting requirements for the #{name} version:)
-          else
-            %(#{solver_name} could not find compatible versions for #{possibility_type} "#{name}":)
-          end
+
+          o
         end
       )
     end
diff --git a/lib/bundler/resolver/spec_group.rb b/lib/bundler/resolver/spec_group.rb
index 232520de77..18ab5a52a3 100644
--- a/lib/bundler/resolver/spec_group.rb
+++ b/lib/bundler/resolver/spec_group.rb
@@ -97,10 +97,10 @@ module Bundler
         spec = @specs[platform].first
         return [] if spec.is_a?(LazySpecification)
         dependencies = []
-        if !spec.required_ruby_version.nil? && !spec.required_ruby_version.none?
+        unless spec.required_ruby_version.none?
           dependencies << DepProxy.get_proxy(Gem::Dependency.new("Ruby\0", spec.required_ruby_version), platform)
         end
-        if !spec.required_rubygems_version.nil? && !spec.required_rubygems_version.none?
+        unless spec.required_rubygems_version.none?
           dependencies << DepProxy.get_proxy(Gem::Dependency.new("RubyGems\0", spec.required_rubygems_version), platform)
         end
         dependencies
diff --git a/lib/bundler/ruby_version.rb b/lib/bundler/ruby_version.rb
index d3b7963920..3f51cf4528 100644
--- a/lib/bundler/ruby_version.rb
+++ b/lib/bundler/ruby_version.rb
@@ -110,19 +110,6 @@ module Bundler
       @ruby_version ||= RubyVersion.new(ruby_version, patchlevel, ruby_engine, ruby_engine_version)
     end
 
-    def to_gem_version_with_patchlevel
-      @gem_version_with_patch ||= begin
-        Gem::Version.create("#{@gem_version}.#{@patchlevel}")
-      rescue ArgumentError
-        @gem_version
-      end
-    end
-
-    def exact?
-      return @exact if defined?(@exact)
-      @exact = versions.all? {|v| Gem::Requirement.create(v).exact? }
-    end
-
     private
 
     def matches?(requirements, version)
diff --git a/lib/bundler/rubygems_ext.rb b/lib/bundler/rubygems_ext.rb
index 78422ceb76..b0e35e005e 100644
--- a/lib/bundler/rubygems_ext.rb
+++ b/lib/bundler/rubygems_ext.rb
@@ -67,6 +67,23 @@ module Gem
       full_gem_path
     end
 
+    unless const_defined?(:LATEST_RUBY_WITHOUT_PATCH_VERSIONS)
+      LATEST_RUBY_WITHOUT_PATCH_VERSIONS = Gem::Version.new("2.1")
+
+      alias_method :rg_required_ruby_version=, :required_ruby_version=
+      def required_ruby_version=(req)
+        self.rg_required_ruby_version = req
+
+        @required_ruby_version.requirements.map! do |op, v|
+          if v >= LATEST_RUBY_WITHOUT_PATCH_VERSIONS && v.release.segments.size == 4
+            [op == "~>" ? "=" : op, Gem::Version.new(v.segments.tap {|s| s.delete_at(3) }.join("."))]
+          else
+            [op, v]
+          end
+        end
+      end
+    end
+
     def groups
       @groups ||= []
     end
diff --git a/lib/bundler/source/metadata.rb b/lib/bundler/source/metadata.rb
index 524afd750a..185fe70824 100644
--- a/lib/bundler/source/metadata.rb
+++ b/lib/bundler/source/metadata.rb
@@ -5,7 +5,7 @@ module Bundler
     class Metadata < Source
       def specs
         @specs ||= Index.build do |idx|
-          idx << Gem::Specification.new("Ruby\0", RubyVersion.system.to_gem_version_with_patchlevel)
+          idx << Gem::Specification.new("Ruby\0", RubyVersion.system.gem_version)
           idx << Gem::Specification.new("RubyGems\0", Gem::VERSION) do |s|
             s.required_rubygems_version = Gem::Requirement.default
           end
diff --git a/lib/bundler/vendor/molinillo/lib/molinillo/dependency_graph.rb b/lib/bundler/vendor/molinillo/lib/molinillo/dependency_graph.rb
index 10a25d2f08..4d577213b9 100644
--- a/lib/bundler/vendor/molinillo/lib/molinillo/dependency_graph.rb
+++ b/lib/bundler/vendor/molinillo/lib/molinillo/dependency_graph.rb
@@ -32,7 +32,7 @@ module Bundler::Molinillo
     #   all belong to the same graph.
     # @return [Array<Vertex>] The sorted vertices.
     def self.tsort(vertices)
-      TSort.tsort(
+      Bundler::TSort.tsort(
         lambda { |b| vertices.each(&b) },
         lambda { |v, &b| (v.successors & vertices).each(&b) }
       )
diff --git a/lib/bundler/vendor/molinillo/lib/molinillo/errors.rb b/lib/bundler/vendor/molinillo/lib/molinillo/errors.rb
index e210202b69..8c8cafb447 100644
--- a/lib/bundler/vendor/molinillo/lib/molinillo/errors.rb
+++ b/lib/bundler/vendor/molinillo/lib/molinillo/errors.rb
@@ -107,36 +107,42 @@ module Bundler::Molinillo
         end
       end
 
-      conflicts.sort.reduce(''.dup) do |o, (name, conflict)|
-        o << "\n" << incompatible_version_message_for_conflict.call(name, conflict) << "\n"
-        if conflict.locked_requirement
-          o << %(  In snapshot (#{name_for_locking_dependency_source}):\n)
-          o << %(    #{printable_requirement.call(conflict.locked_requirement)}\n)
-          o << %(\n)
-        end
-        o << %(  In #{name_for_explicit_dependency_source}:\n)
-        trees = reduce_trees.call(conflict.requirement_trees)
-
-        o << trees.map do |tree|
-          t = ''.dup
-          depth = 2
-          tree.each do |req|
-            t << '  ' * depth << printable_requirement.call(req)
-            unless tree.last == req
-              if spec = conflict.activated_by_name[name_for(req)]
-                t << %( was resolved to #{version_for_spec.call(spec)}, which)
+      full_message_for_conflict = opts.delete(:full_message_for_conflict) do
+        proc do |name, conflict|
+          o = "\n".dup << incompatible_version_message_for_conflict.call(name, conflict) << "\n"
+          if conflict.locked_requirement
+            o << %(  In snapshot (#{name_for_locking_dependency_source}):\n)
+            o << %(    #{printable_requirement.call(conflict.locked_requirement)}\n)
+            o << %(\n)
+          end
+          o << %(  In #{name_for_explicit_dependency_source}:\n)
+          trees = reduce_trees.call(conflict.requirement_trees)
+
+          o << trees.map do |tree|
+            t = ''.dup
+            depth = 2
+            tree.each do |req|
+              t << '  ' * depth << printable_requirement.call(req)
+              unless tree.last == req
+                if spec = conflict.activated_by_name[name_for(req)]
+                  t << %( was resolved to #{version_for_spec.call(spec)}, which)
+                end
+                t << %( depends on)
               end
-              t << %( depends on)
+              t << %(\n)
+              depth += 1
             end
-            t << %(\n)
-            depth += 1
-          end
-          t
-        end.join("\n")
+            t
+          end.join("\n")
 
-        additional_message_for_conflict.call(o, name, conflict)
+          additional_message_for_conflict.call(o, name, conflict)
 
-        o
+          o
+        end
+      end
+
+      conflicts.sort.reduce(''.dup) do |o, (name, conflict)|
+        o << full_message_for_conflict.call(name, conflict)
       end.strip
     end
   end
diff --git a/lib/bundler/vendor/molinillo/lib/molinillo/gem_metadata.rb b/lib/bundler/vendor/molinillo/lib/molinillo/gem_metadata.rb
index e13a781a50..a0cfc21672 100644
--- a/lib/bundler/vendor/molinillo/lib/molinillo/gem_metadata.rb
+++ b/lib/bundler/vendor/molinillo/lib/molinillo/gem_metadata.rb
@@ -2,5 +2,5 @@
 
 module Bundler::Molinillo
   # The version of Bundler::Molinillo.
-  VERSION = '0.7.0'.freeze
+  VERSION = '0.8.0'.freeze
 end
diff --git a/lib/bundler/vendor/tsort/lib/tsort.rb b/lib/bundler/vendor/tsort/lib/tsort.rb
index 8454583295..4a0e1a4e25 100644
--- a/lib/bundler/vendor/tsort/lib/tsort.rb
+++ b/lib/bundler/vendor/tsort/lib/tsort.rb
@@ -6,24 +6,24 @@
 #
 
 #
-# TSort implements topological sorting using Tarjan's algorithm for
+# Bundler::TSort implements topological sorting using Tarjan's algorithm for
 # strongly connected components.
 #
-# TSort is designed to be able to be used with any object which can be
+# Bundler::TSort is designed to be able to be used with any object which can be
 # interpreted as a directed graph.
 #
-# TSort requires two methods to interpret an object as a graph,
+# Bundler::TSort requires two methods to interpret an object as a graph,
 # tsort_each_node and tsort_each_child.
 #
 # * tsort_each_node is used to iterate for all nodes over a graph.
 # * tsort_each_child is used to iterate for child nodes of a given node.
 #
 # The equality of nodes are defined by eql? and hash since
-# TSort uses Hash internally.
+# Bundler::TSort uses Hash internally.
 #
 # == A Simple Example
 #
-# The following example demonstrates how to mix the TSort module into an
+# The following example demonstrates how to mix the Bundler::TSort module into an
 # existing class (in this case, Hash). Here, we're treating each key in
 # the hash as a node in the graph, and so we simply alias the required
 # #tsort_each_node method to Hash's #each_key method. For each key in the
@@ -32,10 +32,10 @@
 # method, which fetches the array of child nodes and then iterates over that
 # array using the user-supplied block.
 #
-#   require 'tsort'
+#   require 'bundler/vendor/tsort/lib/tsort'
 #
 #   class Hash
-#     include TSort
+#     include Bundler::TSort
 #     alias tsort_each_node each_key
 #     def tsort_each_child(node, &block)
 #       fetch(node).each(&block)
@@ -52,7 +52,7 @@
 #
 # A very simple `make' like tool can be implemented as follows:
 #
-#   require 'tsort'
+#   require 'bundler/vendor/tsort/lib/tsort'
 #
 #   class Make
 #     def initialize
@@ -70,7 +70,7 @@
 #       each_strongly_connected_component_from(target) {|ns|
 #         if ns.length != 1
 #           fs = ns.delete_if {|n| Array === n}
-#           raise TSort::Cyclic.new("cyclic dependencies: #{fs.join ', '}")
+#           raise Bundler::TSort::Cyclic.new("cyclic dependencies: #{fs.join ', '}")
 #         end
 #         n = ns.first
 #         if Array === n
@@ -93,7 +93,7 @@
 #     def tsort_each_child(node, &block)
 #       @dep[node].each(&block)
 #     end
-#     include TSort
+#     include Bundler::TSort
 #   end
 #
 #   def command(arg)
@@ -120,334 +120,333 @@
 # R. E. Tarjan, "Depth First Search and Linear Graph Algorithms",
 # <em>SIAM Journal on Computing</em>, Vol. 1, No. 2, pp. 146-160, June 1972.
 #
-module Bundler
-  module TSort
-    class Cyclic < StandardError
-    end
 
-    # Returns a topologically sorted array of nodes.
-    # The array is sorted from children to parents, i.e.
-    # the first element has no child and the last node has no parent.
-    #
-    # If there is a cycle, TSort::Cyclic is raised.
-    #
-    #   class G
-    #     include TSort
-    #     def initialize(g)
-    #       @g = g
-    #     end
-    #     def tsort_each_child(n, &b) @g[n].each(&b) end
-    #     def tsort_each_node(&b) @g.each_key(&b) end
-    #   end
-    #
-    #   graph = G.new({1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]})
-    #   p graph.tsort #=> [4, 2, 3, 1]
-    #
-    #   graph = G.new({1=>[2], 2=>[3, 4], 3=>[2], 4=>[]})
-    #   p graph.tsort # raises TSort::Cyclic
-    #
-    def tsort
-      each_node = method(:tsort_each_node)
-      each_child = method(:tsort_each_child)
-      TSort.tsort(each_node, each_child)
-    end
+module Bundler::TSort
+  class Cyclic < StandardError
+  end
 
-    # Returns a topologically sorted array of nodes.
-    # The array is sorted from children to parents, i.e.
-    # the first element has no child and the last node has no parent.
-    #
-    # The graph is represented by _each_node_ and _each_child_.
-    # _each_node_ should have +call+ method which yields for each node in the graph.
-    # _each_child_ should have +call+ method which takes a node argument and yields for each child node.
-    #
-    # If there is a cycle, TSort::Cyclic is raised.
-    #
-    #   g = {1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]}
-    #   each_node = lambda {|&b| g.each_key(&b) }
-    #   each_child = lambda {|n, &b| g[n].each(&b) }
-    #   p TSort.tsort(each_node, each_child) #=> [4, 2, 3, 1]
-    #
-    #   g = {1=>[2], 2=>[3, 4], 3=>[2], 4=>[]}
-    #   each_node = lambda {|&b| g.each_key(&b) }
-    #   each_child = lambda {|n, &b| g[n].each(&b) }
-    #   p TSort.tsort(each_node, each_child) # raises TSort::Cyclic
-    #
-    def TSort.tsort(each_node, each_child)
-      TSort.tsort_each(each_node, each_child).to_a
-    end
+  # Returns a topologically sorted array of nodes.
+  # The array is sorted from children to parents, i.e.
+  # the first element has no child and the last node has no parent.
+  #
+  # If there is a cycle, Bundler::TSort::Cyclic is raised.
+  #
+  #   class G
+  #     include Bundler::TSort
+  #     def initialize(g)
+  #       @g = g
+  #     end
+  #     def tsort_each_child(n, &b) @g[n].each(&b) end
+  #     def tsort_each_node(&b) @g.each_key(&b) end
+  #   end
+  #
+  #   graph = G.new({1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]})
+  #   p graph.tsort #=> [4, 2, 3, 1]
+  #
+  #   graph = G.new({1=>[2], 2=>[3, 4], 3=>[2], 4=>[]})
+  #   p graph.tsort # raises Bundler::TSort::Cyclic
+  #
+  def tsort
+    each_node = method(:tsort_each_node)
+    each_child = method(:tsort_each_child)
+    Bundler::TSort.tsort(each_node, each_child)
+  end
 
-    # The iterator version of the #tsort method.
-    # <tt><em>obj</em>.tsort_each</tt> is similar to <tt><em>obj</em>.tsort.each</tt>, but
-    # modification of _obj_ during the iteration may lead to unexpected results.
-    #
-    # #tsort_each returns +nil+.
-    # If there is a cycle, TSort::Cyclic is raised.
-    #
-    #   class G
-    #     include TSort
-    #     def initialize(g)
-    #       @g = g
-    #     end
-    #     def tsort_each_child(n, &b) @g[n].each(&b) end
-    #     def tsort_each_node(&b) @g.each_key(&b) end
-    #   end
-    #
-    #   graph = G.new({1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]})
-    #   graph.tsort_each {|n| p n }
-    #   #=> 4
-    #   #   2
-    #   #   3
-    #   #   1
-    #
-    def tsort_each(&block) # :yields: node
-      each_node = method(:tsort_each_node)
-      each_child = method(:tsort_each_child)
-      TSort.tsort_each(each_node, each_child, &block)
-    end
+  # Returns a topologically sorted array of nodes.
+  # The array is sorted from children to parents, i.e.
+  # the first element has no child and the last node has no parent.
+  #
+  # The graph is represented by _each_node_ and _each_child_.
+  # _each_node_ should have +call+ method which yields for each node in the graph.
+  # _each_child_ should have +call+ method which takes a node argument and yields for each child node.
+  #
+  # If there is a cycle, Bundler::TSort::Cyclic is raised.
+  #
+  #   g = {1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]}
+  #   each_node = lambda {|&b| g.each_key(&b) }
+  #   each_child = lambda {|n, &b| g[n].each(&b) }
+  #   p Bundler::TSort.tsort(each_node, each_child) #=> [4, 2, 3, 1]
+  #
+  #   g = {1=>[2], 2=>[3, 4], 3=>[2], 4=>[]}
+  #   each_node = lambda {|&b| g.each_key(&b) }
+  #   each_child = lambda {|n, &b| g[n].each(&b) }
+  #   p Bundler::TSort.tsort(each_node, each_child) # raises Bundler::TSort::Cyclic
+  #
+  def self.tsort(each_node, each_child)
+    tsort_each(each_node, each_child).to_a
+  end
 
-    # The iterator version of the TSort.tsort method.
-    #
-    # The graph is represented by _each_node_ and _each_child_.
-    # _each_node_ should have +call+ method which yields for each node in the graph.
-    # _each_child_ should have +call+ method which takes a node argument and yields for each child node.
-    #
-    #   g = {1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]}
-    #   each_node = lambda {|&b| g.each_key(&b) }
-    #   each_child = lambda {|n, &b| g[n].each(&b) }
-    #   TSort.tsort_each(each_node, each_child) {|n| p n }
-    #   #=> 4
-    #   #   2
-    #   #   3
-    #   #   1
-    #
-    def TSort.tsort_each(each_node, each_child) # :yields: node
-      return to_enum(__method__, each_node, each_child) unless block_given?
+  # The iterator version of the #tsort method.
+  # <tt><em>obj</em>.tsort_each</tt> is similar to <tt><em>obj</em>.tsort.each</tt>, but
+  # modification of _obj_ during the iteration may lead to unexpected results.
+  #
+  # #tsort_each returns +nil+.
+  # If there is a cycle, Bundler::TSort::Cyclic is raised.
+  #
+  #   class G
+  #     include Bundler::TSort
+  #     def initialize(g)
+  #       @g = g
+  #     end
+  #     def tsort_each_child(n, &b) @g[n].each(&b) end
+  #     def tsort_each_node(&b) @g.each_key(&b) end
+  #   end
+  #
+  #   graph = G.new({1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]})
+  #   graph.tsort_each {|n| p n }
+  #   #=> 4
+  #   #   2
+  #   #   3
+  #   #   1
+  #
+  def tsort_each(&block) # :yields: node
+    each_node = method(:tsort_each_node)
+    each_child = method(:tsort_each_child)
+    Bundler::TSort.tsort_each(each_node, each_child, &block)
+  end
 
-      TSort.each_strongly_connected_component(each_node, each_child) {|component|
-        if component.size == 1
-          yield component.first
-        else
-          raise Cyclic.new("topological sort failed: #{component.inspect}")
-        end
-      }
-    end
+  # The iterator version of the Bundler::TSort.tsort method.
+  #
+  # The graph is represented by _each_node_ and _each_child_.
+  # _each_node_ should have +call+ method which yields for each node in the graph.
+  # _each_child_ should have +call+ method which takes a node argument and yields for each child node.
+  #
+  #   g = {1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]}
+  #   each_node = lambda {|&b| g.each_key(&b) }
+  #   each_child = lambda {|n, &b| g[n].each(&b) }
+  #   Bundler::TSort.tsort_each(each_node, each_child) {|n| p n }
+  #   #=> 4
+  #   #   2
+  #   #   3
+  #   #   1
+  #
+  def self.tsort_each(each_node, each_child) # :yields: node
+    return to_enum(__method__, each_node, each_child) unless block_given?
 
-    # Returns strongly connected components as an array of arrays of nodes.
-    # The array is sorted from children to parents.
-    # Each elements of the array represents a strongly connected component.
-    #
-    #   class G
-    #     include TSort
-    #     def initialize(g)
-    #       @g = g
-    #     end
-    #     def tsort_each_child(n, &b) @g[n].each(&b) end
-    #     def tsort_each_node(&b) @g.each_key(&b) end
-    #   end
-    #
-    #   graph = G.new({1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]})
-    #   p graph.strongly_connected_components #=> [[4], [2], [3], [1]]
-    #
-    #   graph = G.new({1=>[2], 2=>[3, 4], 3=>[2], 4=>[]})
-    #   p graph.strongly_connected_components #=> [[4], [2, 3], [1]]
-    #
-    def strongly_connected_components
-      each_node = method(:tsort_each_node)
-      each_child = method(:tsort_each_child)
-      TSort.strongly_connected_components(each_node, each_child)
-    end
+    each_strongly_connected_component(each_node, each_child) {|component|
+      if component.size == 1
+        yield component.first
+      else
+        raise Cyclic.new("topological sort failed: #{component.inspect}")
+      end
+    }
+  end
 
-    # Returns strongly connected components as an array of arrays of nodes.
-    # The array is sorted from children to parents.
-    # Each elements of the array represents a strongly connected component.
-    #
-    # The graph is represented by _each_node_ and _each_child_.
-    # _each_node_ should have +call+ method which yields for each node in the graph.
-    # _each_child_ should have +call+ method which takes a node argument and yields for each child node.
-    #
-    #   g = {1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]}
-    #   each_node = lambda {|&b| g.each_key(&b) }
-    #   each_child = lambda {|n, &b| g[n].each(&b) }
-    #   p TSort.strongly_connected_components(each_node, each_child)
-    #   #=> [[4], [2], [3], [1]]
-    #
-    #   g = {1=>[2], 2=>[3, 4], 3=>[2], 4=>[]}
-    #   each_node = lambda {|&b| g.each_key(&b) }
-    #   each_child = lambda {|n, &b| g[n].each(&b) }
-    #   p TSort.strongly_connected_components(each_node, each_child)
-    #   #=> [[4], [2, 3], [1]]
-    #
-    def TSort.strongly_connected_components(each_node, each_child)
-      TSort.each_strongly_connected_component(each_node, each_child).to_a
-    end
+  # Returns strongly connected components as an array of arrays of nodes.
+  # The array is sorted from children to parents.
+  # Each elements of the array represents a strongly connected component.
+  #
+  #   class G
+  #     include Bundler::TSort
+  #     def initialize(g)
+  #       @g = g
+  #     end
+  #     def tsort_each_child(n, &b) @g[n].each(&b) end
+  #     def tsort_each_node(&b) @g.each_key(&b) end
+  #   end
+  #
+  #   graph = G.new({1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]})
+  #   p graph.strongly_connected_components #=> [[4], [2], [3], [1]]
+  #
+  #   graph = G.new({1=>[2], 2=>[3, 4], 3=>[2], 4=>[]})
+  #   p graph.strongly_connected_components #=> [[4], [2, 3], [1]]
+  #
+  def strongly_connected_components
+    each_node = method(:tsort_each_node)
+    each_child = method(:tsort_each_child)
+    Bundler::TSort.strongly_connected_components(each_node, each_child)
+  end
 
-    # The iterator version of the #strongly_connected_components method.
-    # <tt><em>obj</em>.each_strongly_connected_component</tt> is similar to
-    # <tt><em>obj</em>.strongly_connected_components.each</tt>, but
-    # modification of _obj_ during the iteration may lead to unexpected results.
-    #
-    # #each_strongly_connected_component returns +nil+.
-    #
-    #   class G
-    #     include TSort
-    #     def initialize(g)
-    #       @g = g
-    #     end
-    #     def tsort_each_child(n, &b) @g[n].each(&b) end
-    #     def tsort_each_node(&b) @g.each_key(&b) end
-    #   end
-    #
-    #   graph = G.new({1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]})
-    #   graph.each_strongly_connected_component {|scc| p scc }
-    #   #=> [4]
-    #   #   [2]
-    #   #   [3]
-    #   #   [1]
-    #
-    #   graph = G.new({1=>[2], 2=>[3, 4], 3=>[2], 4=>[]})
-    #   graph.each_strongly_connected_component {|scc| p scc }
-    #   #=> [4]
-    #   #   [2, 3]
-    #   #   [1]
-    #
-    def each_strongly_connected_component(&block) # :yields: nodes
-      each_node = method(:tsort_each_node)
-      each_child = method(:tsort_each_child)
-      TSort.each_strongly_connected_component(each_node, each_child, &block)
-    end
+  # Returns strongly connected components as an array of arrays of nodes.
+  # The array is sorted from children to parents.
+  # Each elements of the array represents a strongly connected component.
+  #
+  # The graph is represented by _each_node_ and _each_child_.
+  # _each_node_ should have +call+ method which yields for each node in the graph.
+  # _each_child_ should have +call+ method which takes a node argument and yields for each child node.
+  #
+  #   g = {1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]}
+  #   each_node = lambda {|&b| g.each_key(&b) }
+  #   each_child = lambda {|n, &b| g[n].each(&b) }
+  #   p Bundler::TSort.strongly_connected_components(each_node, each_child)
+  #   #=> [[4], [2], [3], [1]]
+  #
+  #   g = {1=>[2], 2=>[3, 4], 3=>[2], 4=>[]}
+  #   each_node = lambda {|&b| g.each_key(&b) }
+  #   each_child = lambda {|n, &b| g[n].each(&b) }
+  #   p Bundler::TSort.strongly_connected_components(each_node, each_child)
+  #   #=> [[4], [2, 3], [1]]
+  #
+  def self.strongly_connected_components(each_node, each_child)
+    each_strongly_connected_component(each_node, each_child).to_a
+  end
 
-    # The iterator version of the TSort.strongly_connected_components method.
-    #
-    # The graph is represented by _each_node_ and _each_child_.
-    # _each_node_ should have +call+ method which yields for each node in the graph.
-    # _each_child_ should have +call+ method which takes a node argument and yields for each child node.
-    #
-    #   g = {1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]}
-    #   each_node = lambda {|&b| g.each_key(&b) }
-    #   each_child = lambda {|n, &b| g[n].each(&b) }
-    #   TSort.each_strongly_connected_component(each_node, each_child) {|scc| p scc }
-    #   #=> [4]
-    #   #   [2]
-    #   #   [3]
-    #   #   [1]
-    #
-    #   g = {1=>[2], 2=>[3, 4], 3=>[2], 4=>[]}
-    #   each_node = lambda {|&b| g.each_key(&b) }
-    #   each_child = lambda {|n, &b| g[n].each(&b) }
-    #   TSort.each_strongly_connected_component(each_node, each_child) {|scc| p scc }
-    #   #=> [4]
-    #   #   [2, 3]
-    #   #   [1]
-    #
-    def TSort.each_strongly_connected_component(each_node, each_child) # :yields: nodes
-      return to_enum(__method__, each_node, each_child) unless block_given?
+  # The iterator version of the #strongly_connected_components method.
+  # <tt><em>obj</em>.each_strongly_connected_component</tt> is similar to
+  # <tt><em>obj</em>.strongly_connected_components.each</tt>, but
+  # modification of _obj_ during the iteration may lead to unexpected results.
+  #
+  # #each_strongly_connected_component returns +nil+.
+  #
+  #   class G
+  #     include Bundler::TSort
+  #     def initialize(g)
+  #       @g = g
+  #     end
+  #     def tsort_each_child(n, &b) @g[n].each(&b) end
+  #     def tsort_each_node(&b) @g.each_key(&b) end
+  #   end
+  #
+  #   graph = G.new({1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]})
+  #   graph.each_strongly_connected_component {|scc| p scc }
+  #   #=> [4]
+  #   #   [2]
+  #   #   [3]
+  #   #   [1]
+  #
+  #   graph = G.new({1=>[2], 2=>[3, 4], 3=>[2], 4=>[]})
+  #   graph.each_strongly_connected_component {|scc| p scc }
+  #   #=> [4]
+  #   #   [2, 3]
+  #   #   [1]
+  #
+  def each_strongly_connected_component(&block) # :yields: nodes
+    each_node = method(:tsort_each_node)
+    each_child = method(:tsort_each_child)
+    Bundler::TSort.each_strongly_connected_component(each_node, each_child, &block)
+  end
 
-      id_map = {}
-      stack = []
-      each_node.call {|node|
-        unless id_map.include? node
-          TSort.each_strongly_connected_component_from(node, each_child, id_map, stack) {|c|
-            yield c
-          }
-        end
-      }
-      nil
-    end
+  # The iterator version of the Bundler::TSort.strongly_connected_components method.
+  #
+  # The graph is represented by _each_node_ and _each_child_.
+  # _each_node_ should have +call+ method which yields for each node in the graph.
+  # _each_child_ should have +call+ method which takes a node argument and yields for each child node.
+  #
+  #   g = {1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]}
+  #   each_node = lambda {|&b| g.each_key(&b) }
+  #   each_child = lambda {|n, &b| g[n].each(&b) }
+  #   Bundler::TSort.each_strongly_connected_component(each_node, each_child) {|scc| p scc }
+  #   #=> [4]
+  #   #   [2]
+  #   #   [3]
+  #   #   [1]
+  #
+  #   g = {1=>[2], 2=>[3, 4], 3=>[2], 4=>[]}
+  #   each_node = lambda {|&b| g.each_key(&b) }
+  #   each_child = lambda {|n, &b| g[n].each(&b) }
+  #   Bundler::TSort.each_strongly_connected_component(each_node, each_child) {|scc| p scc }
+  #   #=> [4]
+  #   #   [2, 3]
+  #   #   [1]
+  #
+  def self.each_strongly_connected_component(each_node, each_child) # :yields: nodes
+    return to_enum(__method__, each_node, each_child) unless block_given?
 
-    # Iterates over strongly connected component in the subgraph reachable from
-    # _node_.
-    #
-    # Return value is unspecified.
-    #
-    # #each_strongly_connected_component_from doesn't call #tsort_each_node.
-    #
-    #   class G
-    #     include TSort
-    #     def initialize(g)
-    #       @g = g
-    #     end
-    #     def tsort_each_child(n, &b) @g[n].each(&b) end
-    #     def tsort_each_node(&b) @g.each_key(&b) end
-    #   end
-    #
-    #   graph = G.new({1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]})
-    #   graph.each_strongly_connected_component_from(2) {|scc| p scc }
-    #   #=> [4]
-    #   #   [2]
-    #
-    #   graph = G.new({1=>[2], 2=>[3, 4], 3=>[2], 4=>[]})
-    #   graph.each_strongly_connected_component_from(2) {|scc| p scc }
-    #   #=> [4]
-    #   #   [2, 3]
-    #
-    def each_strongly_connected_component_from(node, id_map={}, stack=[], &block) # :yields: nodes
-      TSort.each_strongly_connected_component_from(node, method(:tsort_each_child), id_map, stack, &block)
-    end
+    id_map = {}
+    stack = []
+    each_node.call {|node|
+      unless id_map.include? node
+        each_strongly_connected_component_from(node, each_child, id_map, stack) {|c|
+          yield c
+        }
+      end
+    }
+    nil
+  end
 
-    # Iterates over strongly connected components in a graph.
-    # The graph is represented by _node_ and _each_child_.
-    #
-    # _node_ is the first node.
-    # _each_child_ should have +call+ method which takes a node argument
-    # and yields for each child node.
-    #
-    # Return value is unspecified.
-    #
-    # #TSort.each_strongly_connected_component_from is a class method and
-    # it doesn't need a class to represent a graph which includes TSort.
-    #
-    #   graph = {1=>[2], 2=>[3, 4], 3=>[2], 4=>[]}
-    #   each_child = lambda {|n, &b| graph[n].each(&b) }
-    #   TSort.each_strongly_connected_component_from(1, each_child) {|scc|
-    #     p scc
-    #   }
-    #   #=> [4]
-    #   #   [2, 3]
-    #   #   [1]
-    #
-    def TSort.each_strongly_connected_component_from(node, each_child, id_map={}, stack=[]) # :yields: nodes
-      return to_enum(__method__, node, each_child, id_map, stack) unless block_given?
+  # Iterates over strongly connected component in the subgraph reachable from
+  # _node_.
+  #
+  # Return value is unspecified.
+  #
+  # #each_strongly_connected_component_from doesn't call #tsort_each_node.
+  #
+  #   class G
+  #     include Bundler::TSort
+  #     def initialize(g)
+  #       @g = g
+  #     end
+  #     def tsort_each_child(n, &b) @g[n].each(&b) end
+  #     def tsort_each_node(&b) @g.each_key(&b) end
+  #   end
+  #
+  #   graph = G.new({1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]})
+  #   graph.each_strongly_connected_component_from(2) {|scc| p scc }
+  #   #=> [4]
+  #   #   [2]
+  #
+  #   graph = G.new({1=>[2], 2=>[3, 4], 3=>[2], 4=>[]})
+  #   graph.each_strongly_connected_component_from(2) {|scc| p scc }
+  #   #=> [4]
+  #   #   [2, 3]
+  #
+  def each_strongly_connected_component_from(node, id_map={}, stack=[], &block) # :yields: nodes
+    Bundler::TSort.each_strongly_connected_component_from(node, method(:tsort_each_child), id_map, stack, &block)
+  end
 
-      minimum_id = node_id = id_map[node] = id_map.size
-      stack_length = stack.length
-      stack << node
+  # Iterates over strongly connected components in a graph.
+  # The graph is represented by _node_ and _each_child_.
+  #
+  # _node_ is the first node.
+  # _each_child_ should have +call+ method which takes a node argument
+  # and yields for each child node.
+  #
+  # Return value is unspecified.
+  #
+  # #Bundler::TSort.each_strongly_connected_component_from is a class method and
+  # it doesn't need a class to represent a graph which includes Bundler::TSort.
+  #
+  #   graph = {1=>[2], 2=>[3, 4], 3=>[2], 4=>[]}
+  #   each_child = lambda {|n, &b| graph[n].each(&b) }
+  #   Bundler::TSort.each_strongly_connected_component_from(1, each_child) {|scc|
+  #     p scc
+  #   }
+  #   #=> [4]
+  #   #   [2, 3]
+  #   #   [1]
+  #
+  def self.each_strongly_connected_component_from(node, each_child, id_map={}, stack=[]) # :yields: nodes
+    return to_enum(__method__, node, each_child, id_map, stack) unless block_given?
 
-      each_child.call(node) {|child|
-        if id_map.include? child
-          child_id = id_map[child]
-          minimum_id = child_id if child_id && child_id < minimum_id
-        else
-          sub_minimum_id =
-            TSort.each_strongly_connected_component_from(child, each_child, id_map, stack) {|c|
-              yield c
-            }
-          minimum_id = sub_minimum_id if sub_minimum_id < minimum_id
-        end
-      }
+    minimum_id = node_id = id_map[node] = id_map.size
+    stack_length = stack.length
+    stack << node
 
-      if node_id == minimum_id
-        component = stack.slice!(stack_length .. -1)
-        component.each {|n| id_map[n] = nil}
-        yield component
+    each_child.call(node) {|child|
+      if id_map.include? child
+        child_id = id_map[child]
+        minimum_id = child_id if child_id && child_id < minimum_id
+      else
+        sub_minimum_id =
+          each_strongly_connected_component_from(child, each_child, id_map, stack) {|c|
+            yield c
+          }
+        minimum_id = sub_minimum_id if sub_minimum_id < minimum_id
       end
+    }
 
-      minimum_id
+    if node_id == minimum_id
+      component = stack.slice!(stack_length .. -1)
+      component.each {|n| id_map[n] = nil}
+      yield component
     end
 
-    # Should be implemented by a extended class.
-    #
-    # #tsort_each_node is used to iterate for all nodes over a graph.
-    #
-    def tsort_each_node # :yields: node
-      raise NotImplementedError.new
-    end
+    minimum_id
+  end
 
-    # Should be implemented by a extended class.
-    #
-    # #tsort_each_child is used to iterate for child nodes of _node_.
-    #
-    def tsort_each_child(node) # :yields: child
-      raise NotImplementedError.new
-    end
+  # Should be implemented by a extended class.
+  #
+  # #tsort_each_node is used to iterate for all nodes over a graph.
+  #
+  def tsort_each_node # :yields: node
+    raise NotImplementedError.new
+  end
+
+  # Should be implemented by a extended class.
+  #
+  # #tsort_each_child is used to iterate for child nodes of _node_.
+  #
+  def tsort_each_child(node) # :yields: child
+    raise NotImplementedError.new
   end
 end