no callbacks should be created for empty array [#5289 state:resolved]

Signed-off-by: NJosé Valim <jose.valim@gmail.com>

activemodel/lib/active_model/callbacks.rb

@@ -90,10 +90,13 @@ def self.extended(base)
     #     
     def define_model_callbacks(*callbacks)
       options = callbacks.extract_options!
-      options = { :terminator => "result == false", :scope => [:kind, :name] }.merge(options)
+      options = { 
+         :terminator => "result == false", 
+         :scope => [:kind, :name], 
+         :only => [:before, :around, :after] 
+      }.merge(options)
 
-      types = Array.wrap(options.delete(:only))
-      types = [:before, :around, :after] if types.empty?
+      types   = Array.wrap(options.delete(:only))
 
       callbacks.each do |callback|
         define_callbacks(callback, options)

activemodel/test/cases/callbacks_test.rb

@@ -16,6 +16,8 @@ class ModelCallbacks
 
     define_model_callbacks :create
     define_model_callbacks :initialize, :only => :after
+    define_model_callbacks :multiple,   :only => [:before, :around]
+    define_model_callbacks :empty,      :only => []
 
     before_create :before_create
     around_create CallbackValidator.new
@@ -67,4 +69,16 @@ def create
     assert !ModelCallbacks.respond_to?(:around_initialize)
     assert_respond_to ModelCallbacks, :after_initialize
   end
+
+  test "only selects which types of callbacks should be created from an array list" do
+    assert_respond_to ModelCallbacks, :before_multiple
+    assert_respond_to ModelCallbacks, :around_multiple
+    assert !ModelCallbacks.respond_to?(:after_multiple)
+  end
+
+  test "no callbacks should be created" do
+    assert !ModelCallbacks.respond_to?(:before_empty)
+    assert !ModelCallbacks.respond_to?(:around_empty)
+    assert !ModelCallbacks.respond_to?(:after_empty)
+  end
 end