Support new onUpload() AJAX handler for uploads instead of postback takeovers.

Fixes #5104. Refs: 4f7e2995c7

modules/cms/widgets/AssetList.php

@@ -57,8 +57,6 @@ class AssetList extends WidgetBase
         parent::__construct($controller, []);
 
         $this->bindToController();
-
-        $this->checkUploadPostback();
     }
 
     /**
@@ -622,10 +620,12 @@ class AssetList extends WidgetBase
     }
 
     /**
-     * Checks the current request to see if it is a postback containing a file upload
-     * for this particular widget.
+     * Process file uploads submitted via AJAX
+     *
+     * @return void
+     * @throws ApplicationException If the file "file_data" wasn't detected in the request or if the file failed to pass validation / security checks
      */
-    protected function checkUploadPostback()
+    public function onUpload()
     {
         $fileName = null;
 

modules/cms/widgets/assetlist/assets/js/assetlist.js

@@ -83,6 +83,9 @@
     }
 
     AssetList.prototype.onUploadFail = function(file, message) {
+        if (file.xhr.status === 413) {
+            message = 'Server rejected the file because it was too large, try increasing post_max_size';
+        }
         if (!message) {
             message = 'Error uploading file'
         }
@@ -170,6 +173,7 @@
             $.each(self.$form.serializeArray(), function (index, field) {
                 formData.append(field.name, field.value)
             })
+            xhr.setRequestHeader('X-OCTOBER-REQUEST-HANDLER', self.alias + '::onUpload')
             self.onUploadStart()
         })
     }