add DRb::WeakIdConv (Bug #15711)

lib/drb/weakidconv.rb

@@ -0,0 +1,59 @@
+# frozen_string_literal: false
+require_relative 'drb'
+require 'monitor'
+
+module DRb
+
+  # To use WeakIdConv:
+  #
+  #  DRb.start_service(nil, nil, {:idconv => DRb::WeakIdConv.new})
+
+  class WeakIdConv < DRbIdConv
+    class WeakSet
+      include MonitorMixin
+      def initialize
+        super()
+        @immutable = {}
+        @map = ObjectSpace::WeakMap.new
+      end
+
+      def add(obj)
+        synchronize do
+          begin
+            @map[obj] = self 
+          rescue ArgumentError
+            @immutable[obj.__id__] = obj
+          end
+          return obj.__id__
+        end
+      end
+
+      def fetch(ref)
+        synchronize do
+          @immutable.fetch(ref) { 
+            @map.each { |key, _|
+              return key if key.__id__ == ref
+            }
+            raise RangeError.new("invalid reference")
+          }
+        end
+      end
+    end
+
+    def initialize()
+      super()
+      @weak_set = WeakSet.new
+    end
+
+    def to_obj(ref) # :nodoc:
+      return super if ref.nil?
+      @weak_set.fetch(ref)
+    end
+
+    def to_id(obj) # :nodoc:
+      return @weak_set.add(obj)
+    end
+  end
+end
+
+# DRb.install_id_conv(WeakIdConv.new)

test/drb/test_drbobject.rb

@@ -1,6 +1,7 @@
 require 'test/unit'
 require 'drb'
 require 'drb/timeridconv'
+require 'drb/weakidconv'
 
 module DRbObjectTest
   class Foo
@@ -45,3 +46,19 @@ class TestDRbObjectTimerIdConv < Test::Unit::TestCase
     DRb.start_service(nil, nil, {:idconv => DRb::TimerIdConv.new})
   end
 end
+
+class TestDRbObjectWeakIdConv < Test::Unit::TestCase
+  include DRbObjectTest
+
+  def setup
+    DRb.start_service(nil, nil, {:idconv => DRb::WeakIdConv.new})
+  end
+
+  def test_RangeError
+    proxy = DRbObject.new("string".dup)
+    GC.start
+    assert_raise(RangeError) {
+      DRb.to_obj(proxy.__drbref)
+    }
+  end
+end