[rubygems/rubygems] Bump Molinillo and tsort

And configure tsort to be vendored as a dependency of Molinillo.

https://github.com/rubygems/rubygems/commit/8ec749f891

4 files changed, 342 insertions, 338 deletions

diff --git a/lib/rubygems/resolver/molinillo/lib/molinillo/dependency_graph.rb b/lib/rubygems/resolver/molinillo/lib/molinillo/dependency_graph.rb
index 95f8416b96..731a9e3e90 100644
--- a/lib/rubygems/resolver/molinillo/lib/molinillo/dependency_graph.rb
+++ b/lib/rubygems/resolver/molinillo/lib/molinillo/dependency_graph.rb
@@ -32,7 +32,7 @@ module Gem::Resolver::Molinillo
     #   all belong to the same graph.
     # @return [Array<Vertex>] The sorted vertices.
     def self.tsort(vertices)
-      TSort.tsort(
+      Gem::TSort.tsort(
         lambda { |b| vertices.each(&b) },
         lambda { |v, &b| (v.successors & vertices).each(&b) }
       )
diff --git a/lib/rubygems/resolver/molinillo/lib/molinillo/errors.rb b/lib/rubygems/resolver/molinillo/lib/molinillo/errors.rb
index ada03a901c..4289902828 100644
--- a/lib/rubygems/resolver/molinillo/lib/molinillo/errors.rb
+++ b/lib/rubygems/resolver/molinillo/lib/molinillo/errors.rb
@@ -107,36 +107,42 @@ module Gem::Resolver::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/rubygems/resolver/molinillo/lib/molinillo/gem_metadata.rb b/lib/rubygems/resolver/molinillo/lib/molinillo/gem_metadata.rb
index 6b5ada7ade..86c249c404 100644
--- a/lib/rubygems/resolver/molinillo/lib/molinillo/gem_metadata.rb
+++ b/lib/rubygems/resolver/molinillo/lib/molinillo/gem_metadata.rb
@@ -2,5 +2,5 @@
 
 module Gem::Resolver::Molinillo
   # The version of Gem::Resolver::Molinillo.
-  VERSION = '0.7.0'.freeze
+  VERSION = '0.8.0'.freeze
 end
diff --git a/lib/rubygems/tsort/lib/tsort.rb b/lib/rubygems/tsort/lib/tsort.rb
index f68c5947d3..f825f14257 100644
--- a/lib/rubygems/tsort/lib/tsort.rb
+++ b/lib/rubygems/tsort/lib/tsort.rb
@@ -121,334 +121,332 @@
 # <em>SIAM Journal on Computing</em>, Vol. 1, No. 2, pp. 146-160, June 1972.
 #
 
-module Gem
-  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, Gem::TSort::Cyclic is raised.
-    #
-    #   class G
-    #     include Gem::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 Gem::TSort::Cyclic
-    #
-    def tsort
-      each_node = method(:tsort_each_node)
-      each_child = method(:tsort_each_child)
-      Gem::TSort.tsort(each_node, each_child)
-    end
+module Gem::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, Gem::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 Gem::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 Gem::TSort.tsort(each_node, each_child) # raises Gem::TSort::Cyclic
-    #
-    def TSort.tsort(each_node, each_child)
-      Gem::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, Gem::TSort::Cyclic is raised.
+  #
+  #   class G
+  #     include Gem::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 Gem::TSort::Cyclic
+  #
+  def tsort
+    each_node = method(:tsort_each_node)
+    each_child = method(:tsort_each_child)
+    Gem::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, Gem::TSort::Cyclic is raised.
-    #
-    #   class G
-    #     include Gem::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)
-      Gem::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, Gem::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 Gem::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 Gem::TSort.tsort(each_node, each_child) # raises Gem::TSort::Cyclic
+  #
+  def self.tsort(each_node, each_child)
+    tsort_each(each_node, each_child).to_a
+  end
 
-    # The iterator version of the Gem::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) }
-    #   Gem::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, Gem::TSort::Cyclic is raised.
+  #
+  #   class G
+  #     include Gem::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)
+    Gem::TSort.tsort_each(each_node, each_child, &block)
+  end
 
-      Gem::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 Gem::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) }
+  #   Gem::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 Gem::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)
-      Gem::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 Gem::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 Gem::TSort.strongly_connected_components(each_node, each_child)
-    #   #=> [[4], [2, 3], [1]]
-    #
-    def TSort.strongly_connected_components(each_node, each_child)
-      Gem::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 Gem::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)
+    Gem::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 Gem::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)
-      Gem::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 Gem::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 Gem::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 Gem::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) }
-    #   Gem::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) }
-    #   Gem::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 Gem::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)
+    Gem::TSort.each_strongly_connected_component(each_node, each_child, &block)
+  end
 
-      id_map = {}
-      stack = []
-      each_node.call {|node|
-        unless id_map.include? node
-          Gem::TSort.each_strongly_connected_component_from(node, each_child, id_map, stack) {|c|
-            yield c
-          }
-        end
-      }
-      nil
-    end
+  # The iterator version of the Gem::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) }
+  #   Gem::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) }
+  #   Gem::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 Gem::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
-      Gem::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.
-    #
-    # #Gem::TSort.each_strongly_connected_component_from is a class method and
-    # it doesn't need a class to represent a graph which includes Gem::TSort.
-    #
-    #   graph = {1=>[2], 2=>[3, 4], 3=>[2], 4=>[]}
-    #   each_child = lambda {|n, &b| graph[n].each(&b) }
-    #   Gem::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 Gem::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
+    Gem::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.
+  #
+  # #Gem::TSort.each_strongly_connected_component_from is a class method and
+  # it doesn't need a class to represent a graph which includes Gem::TSort.
+  #
+  #   graph = {1=>[2], 2=>[3, 4], 3=>[2], 4=>[]}
+  #   each_child = lambda {|n, &b| graph[n].each(&b) }
+  #   Gem::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 =
-            Gem::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