support form attribute for submit buttons

lib/capybara/rack_test/node.rb

@@ -112,7 +112,11 @@ private
   end
 
   def form
-    native.ancestors('form').first
+    if native[:form]
+      native.xpath("//form[@id='#{native[:form]}']").first
+    else
+      native.ancestors('form').first
+    end
   end
 
   def set_radio(value)

lib/capybara/spec/session/click_button_spec.rb

@@ -137,7 +137,7 @@ Capybara::SpecHelper.spec '#click_button' do
       end
     end
   end
-
+  
   context "with id given on a submit button" do
     it "should submit the associated form" do
       @session.click_button('awe123')
@@ -161,7 +161,40 @@ Capybara::SpecHelper.spec '#click_button' do
       extract_results(@session)['first_name'].should == 'John'
     end
   end
+  
+  context "with submit button outside the form defined by <button> tag" do
+    before do
+      @session.click_button('outside_button')
+      @results = extract_results(@session)
+    end
+    
+    it "should submit the associated form" do
+      @results['first_name'].should == 'John'
+    end
+    
+    it "should submit the button that was clicked, but not other buttons" do
+      @results['outside_button'].should == 'outside_button'
+      @results['crappy'].should be_nil
+    end
+  end
 
+  context "with submit button outside the form defined by <input type='submit'> tag" do
+    before do
+      @session.click_button('outside_submit')
+      @results = extract_results(@session)
+    end
+    
+    it "should submit the associated form" do
+      @results['first_name'].should == 'John'
+    end
+    
+    it "should submit the button that was clicked, but not other buttons" do
+      @results['outside_submit'].should == 'outside_submit'
+      @results['crappy'].should be_nil
+    end
+  end
+
+  
   context "with alt given on an image button" do
     it "should submit the associated form" do
       @session.click_button('oh hai thar')

lib/capybara/spec/views/form.erb

@@ -1,6 +1,6 @@
 <h1>Form</h1>
 
-<form action="/form" method="post">
+<form id="the_form" action="/form" method="post">
 
   <p>
     <label for="form_title">Title</label>
@@ -256,6 +256,8 @@
     <input type="button" disabled value="Disabled button"/>
   </p>
 </form>
+<input type="submit" name="form[outside_submit]" value="outside_submit" form="the_form"/>
+<button type="submit" name="form[outside_button]" value="outside_button" form="the_form">Outside!</button>
 
 <form id="get-form" action="/form/get?foo=bar" method="get">
   <p>