727412 - Unnecessary CORS preflight when using upload progress

Status: RESOLVED INVALID

(Core :: DOM: Core & HTML, defect)

Description

[Lukspa]

User Agent: Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:10.0.1) Gecko/20100101 Firefox/10.0.1
Build ID: 20120210021051

Steps to reproduce:

1. Create async POST xhr request with content-type: multipart/form-data
2. set onprogress handler or onloadstart handler on xhr.upload
3. send request

Example code: 
xhr.open("POST", this.uploadScript, true);
xhr.setRequestHeader('Content-type', 'multipart/form-data; boundary=' + boundary);

xhr.onload = this._fileUploadComplete;
xhr.onerror = this._fileUploadError;
xhr.onabort = this._fileUploadAbort;

xhr.upload.onprogress = this._fileUploadProgress; // problem cause
xhr.upload.onloadstart = this._fileUploadLoadStart; // problem cause

xhr.sendAsBinary(this.currItem.postData);


Actual results:

FF sends a OPTIONS preflight with:
Access-Control-Allow-Methods: POST


Expected results:

FF should't send a preflight. Request should be treated as simple CORS request.

Comment 1

[Boris Zbarsky [:bzbarsky]]

From http://www.w3.org/TR/XMLHttpRequest2/#cross-origin-request-steps :

  force preflight flag
      True if the upload events flag is set, or false otherwise. 

And from http://www.w3.org/TR/XMLHttpRequest2/#upload-events-flag :

  Set when event listeners are registered on the XMLHttpRequestUpload object to determine
  whether a preflight request is needed. Initially unset.

So we're just following the spec here.