Default to re-throwing errors that occur inside of Ajax callbacks, rather than silently ignoring them. To restore the old behavior, pass in an empty function to onException. (Closes prototypejs#302)

Author: savetheclocktower

src/prototype/ajax.js

@@ -117,7 +117,10 @@
  *    `onFailure`. Happens _before_ `onComplete`.
  *  * `onException`: Triggered whenever an XHR error arises. Has a custom
  *    signature: the first argument is the requester (i.e. an [[Ajax.Request]]
- *    instance), and the second is the exception object.
+ *    instance), and the second is the exception object. The default
+ *    `onException` handler simply re-throws the caught exception. (If you
+ *    want exceptions to be silently ignored, pass in an empty function to
+ *    `onException`.)
  *  * `onComplete`: Triggered at the _very end_ of a request's life-cycle, after
  *    the request completes, status-specific callbacks are called, and possible
  *    automatic behaviors are processed. Guaranteed to run regardless of what

src/prototype/ajax/base.js

@@ -8,7 +8,10 @@ Ajax.Base = Class.create({
       encoding:     'UTF-8',
       parameters:   '',
       evalJSON:     true,
-      evalJS:       true
+      evalJS:       true,
+      onException: function (request, error) {
+        throw error;
+      }
     };
     Object.extend(this.options, options || { });
 

test/unit/tests/ajax.test.js

@@ -57,8 +57,7 @@ function assertContent(id, content, message) {
 var extendDefault = function(options) {
   return Object.extend({
     asynchronous: false,
-    method: 'get',
-    onException: function(r, e) { throw e; }
+    method: 'get'
   }, options);
 };
 
@@ -110,15 +109,18 @@ suite("Ajax", function () {
       method: 'GET',
       onComplete: function () {
         assert.equal(1, Ajax.activeRequestCount);
+        setTimeout(function () {
+          assert.equal(0, Ajax.activeRequestCount);
+          done();
+        }, 250);
         throw new Error('test');
+      },
+
+      onException: function () {
+        // Empty function to prevent the error from being rethrown
       }
     });
 
-    setTimeout(function () {
-      assert.equal(0, Ajax.activeRequestCount);
-      done();
-    }, 1000);
-
   });
 
   suite('Updater', function () {
@@ -540,5 +542,18 @@ suite("Ajax", function () {
     }));
   });
 
+  test('no exception handler', function (done) {
+    new Ajax.Request('/inspect', extendDefault({
+      onSuccess: function () {
+        try {
+          throw new Error("foo");
+          assert(true);
+        } finally {
+          done();
+        }
+      }
+    }));
+  });
+
 });