I can\'t find any docs about creating dojox/form/Uploader programmatically. I tried it by myself, but it looks like that plugin registering mechanism is somehow broken.
In short; use new dojox.form.Uploader instead of the pulled in variable, otherwise the plugin extending does not apply.
Reason being, you would see programmer doing following in the addUploaderPlugin:
dojox.form.UploaderOrg = dojox.form.Uploader;
var extensions = [dojox.form.UploaderOrg];
dojox.form.addUploaderPlugin = function(plug){
extensions.push(plug);
declare("dojox.form.Uploader", extensions, {});
}
The class that AMD loader returns is and will allways be dojox.form.UploaderOrg and does not know about the extended plugins.
Change to following:
var up = new dojox.form.Uploader({
label: 'Pick files',
multiple: true,
url: '/echo/json/'
}).placeAt(form);
And make sure you have not set djConfig.publishRequireResult = false