Ensure Form.focusFirstElement doesn't raise an exception on forms with no fields. [prototypejs#341 state:resolved] (achernin, Andrew Dupont)

Author: savetheclocktower

CHANGELOG

@@ -1,3 +1,5 @@
+* Ensure `Form.focusFirstElement` doesn't raise an exception on forms with no fields. [#341 state:resolved] (achernin, Andrew Dupont)
+
 * Define a `relatedTarget` property on extended mouseenter/mouseleave events in IE's legacy event system. [#708 state:resolved] (Walter Smith, Tobie Langel, Andrew Dupont)
 
 * Fix odd behavior with `new Element('select')` in IE6-7. [#480 state:resolved] (Bruce Harris, kangax, Andrew Dupont)

src/dom/form.js

@@ -321,7 +321,8 @@ Form.Methods = {
   **/
   focusFirstElement: function(form) {
     form = $(form);
-    form.findFirstElement().activate();
+    var element = form.findFirstElement();
+    if (element) element.activate();
     return form;
   },
 

test/unit/fixtures/form.html

@@ -84,6 +84,8 @@
   <input type="file" name="file_name" value="foo" />
 </form>
 
+<form id="form_empty"></form>
+
 <!-- tabindexed forms -->
 <div id="tabindex">
   <form id="ffe">

test/unit/form_test.js

@@ -180,26 +180,25 @@ new Test.Unit.Runner({
       catch(e){ return null }
     }
 
-    // Form.focusFirstElement shouldn't focus disabled elements
     var element = Form.findFirstElement('bigform');
-    this.assertEqual('submit', element.id);
+    this.assertEqual('submit', element.id, "Form.focusFirstElement shouldn't focus disabled elements");
 
-    // Test IE doesn't select text on buttons
     Form.focusFirstElement('bigform');
-    if(document.selection) this.assertEqual('', getSelection(element));
+    if (document.selection) this.assertEqual('', getSelection(element), "IE shouldn't select text on buttons");
 
-    // Form.Element.activate shouldn't select text on buttons
     element = $('focus_text');
-    this.assertEqual('', getSelection(element));
+    this.assertEqual('', getSelection(element), "Form.Element.activate shouldn't select text on buttons");
 
-    // Form.Element.activate should select text on text input elements
     element.activate();
-    this.assertEqual('Hello', getSelection(element));
+    this.assertEqual('Hello', getSelection(element), "Form.Element.activate should select text on text input elements");
 
-    // Form.Element.activate shouldn't raise an exception when the form or field is hidden
     this.assertNothingRaised(function() {
       $('form_focus_hidden').focusFirstElement();
-    });
+    }, "Form.Element.activate shouldn't raise an exception when the form or field is hidden");
+    
+    this.assertNothingRaised(function() {
+      $('form_empty').focusFirstElement();
+    }, "Form.focusFirstElement shouldn't raise an exception when the form has no fields");
   },
 
   testFormGetElements: function() {