3 files changed, 42 insertions, 12 deletions
diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index d853788e00..0e24cc138a 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -4,7 +4,7 @@
 
 * Ruby 1.9: support UTF-8 case folding.  #4595 [Norman Clarke]
 
-* Renames Array#rand -> Array#random_element. [Santiago Pastorino, Rizwan Reza]
+* Removes Array#rand and backports Array#sample from Ruby 1.9, thanks to Marc-Andre Lafortune. [fxn]
 
 * Ruby 1.9: Renames last_(month|year) to prev_(month|year) in Date and Time. [fxn]
 
diff --git a/activesupport/lib/active_support/core_ext/array/random_access.rb b/activesupport/lib/active_support/core_ext/array/random_access.rb
index 67c322daea..7a4836cecd 100644
--- a/activesupport/lib/active_support/core_ext/array/random_access.rb
+++ b/activesupport/lib/active_support/core_ext/array/random_access.rb
@@ -1,6 +1,20 @@
 class Array
-  # Returns a random element from the array.
-  def random_element
-    self[Kernel.rand(length)]
-  end
+  # Backport of Array#sample based on Marc-Andre Lafortune's http://github.com/marcandre/backports/
+  def sample(n=nil)
+    return self[Kernel.rand(size)] if n.nil?
+    n = n.to_int
+  rescue Exception => e
+    raise TypeError, "Coercion error: #{n.inspect}.to_int => Integer failed:\n(#{e.message})"
+  else
+    raise TypeError, "Coercion error: obj.to_int did NOT return an Integer (was #{n.class})" unless n.kind_of? Integer
+    raise ArgumentError, "negative array size" if n < 0
+    n = size if n > size
+    result = Array.new(self)
+    n.times do |i|
+      r = i + Kernel.rand(size - i)
+      result[i], result[r] = result[r], result[i]
+    end
+    result[n..size] = []
+    result
+  end unless method_defined? :sample
 end
 \ No newline at end of file
diff --git a/activesupport/test/core_ext/array_ext_test.rb b/activesupport/test/core_ext/array_ext_test.rb
index 1f7cdb8ec1..54376deee5 100644
--- a/activesupport/test/core_ext/array_ext_test.rb
+++ b/activesupport/test/core_ext/array_ext_test.rb
@@ -359,14 +359,30 @@ class ArrayUniqByTests < Test::Unit::TestCase
 end
 
 class ArrayExtRandomTests < ActiveSupport::TestCase
-  def test_random_element_from_array
-    assert_nil [].random_element
-
-    Kernel.expects(:rand).with(1).returns(0)
-    assert_equal 'x', ['x'].random_element
+  def test_sample_from_array
+    assert_nil [].sample
+    assert_equal [], [].sample(5)
+    assert_equal 42, [42].sample
+    assert_equal [42], [42].sample(5)
+
+    a = [:foo, :bar, 42]
+    s = a.sample(2)
+    assert_equal 2, s.size
+    assert_equal 1, (a-s).size
+    assert_equal [], a-(0..20).sum{a.sample(2)}
+  
+    o = Object.new
+    def o.to_int; 1; end
+    assert_equal [0], [0].sample(o)
+  
+    o = Object.new
+    assert_raises(TypeError) { [0].sample(o) }
+    
+    o = Object.new
+    def o.to_int; ''; end
+    assert_raises(TypeError) { [0].sample(o) }
 
-    Kernel.expects(:rand).with(3).returns(1)
-    assert_equal 2, [1, 2, 3].random_element
+    assert_raises(ArgumentError) { [0].sample(-7) }
   end
 end