Hi,
I've never posted here before so please forgive me if I'm not
observing proper decorum, yadda yadda yadda :-)
I've ran into a very, very strange bug with Prototype I wanted to
share and see if anyone else has seen this. In a few of my projects
involving Ext JS, I'm using the TreePanel control, which uses AJAX to
load child nodes asynchronously. Because I bundle in the prototype
library with my Ext, these AJAX calls are being processed by Prototype
(v 1.6.0.2). In every instance where I use one of these tree panels,
I've noticed the weirdest problem where every so often, totally at
random, even though the child nodes are sent back correctly by the
server, the tree panel logs an error and the children fail to load.
I've been tracking this for weeks now and finally stumbled upon the
root cause of the problem, and it turns out to be an apparent bug in
Prototype, not in Ext:
In the Ajax.Request class, the respondToReadyState method, you have:
respondToReadyState: function(readyState) {
var state = Ajax.Request.Events[readyState], response = new
Ajax.Response(this);
etc etc etc...
Maybe 90% of the time, readyState here and transport.readyState are
the same (as they always should be?). However, it turns out, maybe
10% of the time the readyState passed into the event handler is
completely different from the ready state in the XHR object
(transport.readyState). I set up a piece of code to log this in
Firebug (but this happens in every browser, mind you):
respondToReadyState: function(readyState) {
if (readyState != this.transport.readyState)
console.log("readyState is " + readyState + " but transport
says "
+ this.transport.readyState + "!!!!!");
And, in the course of perhaps 15 minutes of various ajax requests (not
just in my tree panel, but anywhere), I see this in my console:
readyState is 170 but transport says 1!!!!!
readyState is 7 but transport says 1!!!!!
readyState is 7 but transport says 1!!!!!
readyState is 3 but transport says 1!!!!!
readyState is 4 but transport says 1!!!!!
That last one is the real problem - because readyState is 4 but the
real readyState in the XHR object is still actually 1, the success
callback is triggered (because Ajax.Response checks
transport.readyState, not the readyState passed to
respondToReadyState), but there is no responseText (yet), so the whole
call fails.
Extremely frustrating bug to tease out, let me tell you, because
Firebug *always* seems to get the right responseText, even though
Prototype doesn't. It was easy enough now to fix my problem, all I
did was this:
respondToReadyState: function(readyState) {
readyState = this.transport.readyState;
[ continue on as normal ]
And now I have *no* problems. But I really don't like the idea of
modifying my prototype :-(. So what gives? Can I really be the only
person this is happening to? And what the heck would a readyState of
170 mean anyway? It's super-duper-done?
Thanks for listening, and despite this little glitch, thanks so much
for Prototype! I just can't live without my Enumerables!
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