Ensure only delegations to methods can have an automatic prefix. [#1235 state:resolved]

Signed-off-by: Pratik Naik <pratiknaik@gmail.com>

2 files changed, 15 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/core_ext/module/delegation.rb b/activesupport/lib/active_support/core_ext/module/delegation.rb
index 1ad18402e5..2905eebc85 100644
--- a/activesupport/lib/active_support/core_ext/module/delegation.rb
+++ b/activesupport/lib/active_support/core_ext/module/delegation.rb
@@ -78,6 +78,10 @@ class Module
       raise ArgumentError, "Delegation needs a target. Supply an options hash with a :to key as the last argument (e.g. delegate :hello, :to => :greeter)."
     end
 
+    if options[:prefix] == true && options[:to].to_s =~ /^[^a-z_]/
+      raise ArgumentError, "Can only automatically set the delegation prefix when delegating to a method."
+    end
+
     prefix = options[:prefix] && "#{options[:prefix] == true ? to : options[:prefix]}_"
 
     methods.each do |method|
diff --git a/activesupport/test/core_ext/module_test.rb b/activesupport/test/core_ext/module_test.rb
index 7fe5d0faee..886f692499 100644
--- a/activesupport/test/core_ext/module_test.rb
+++ b/activesupport/test/core_ext/module_test.rb
@@ -106,6 +106,17 @@ class ModuleTest < Test::Unit::TestCase
     assert_equal invoice.customer_city, "Chicago"
   end
 
+  def test_delegation_prefix_with_instance_variable
+    assert_raise ArgumentError do
+      Class.new do
+        def initialize(client)
+          @client = client
+        end
+        delegate :name, :address, :to => :@client, :prefix => true
+      end
+    end
+  end
+
   def test_parent
     assert_equal Yz::Zy, Yz::Zy::Cd.parent
     assert_equal Yz, Yz::Zy.parent