IssueTracker

What steps will reproduce the problem?
1. Use UrlFetchApp.fetch() for a POST request.
2. Server responds with Location + 2 cookies:
     Location:https://www.same-server.com/redirected_page.html
     Set-Cookie:PHPSESSID=c5236...
     Set-Cookie:ticket=e1c77...
3. Google automatically requests the page from the redirected location,
   but only sends one of the received cookie to the server.
4. The web server is confused and strange things happen ...
5. Example script:
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function tst_followPageLogin() {
  // to test this, you have to register at followthatpage.com and
  // put your login/pasword in line 10+11.
  var url = "https://www.followthatpage.com/";    
  var options = {}; // for UrlFetchApp.fetch
  options.headers = {};
  options.headers.Referer = "https://www.followthatpage.com/login";
  options.method = "post";
  options.payload = "_qf__login=&action=login&remember_password=1"+
    "&email=" + fixedEncodeURIComponent("my-email@...com") +
    "&password=" + fixedEncodeURIComponent("my-password");
 
  Logger.log("UrlFetchApp.fetch('" + url + "', " + options.toSource());
 
  var response = UrlFetchApp.fetch(url, options);
  // => Exception "Too many redirects: https://www.followthatpage.com/list_pages"
  //    (with incorrect login, simply returns "... Password is not correct...")
 
  Logger.log("Web Page:\n" + response.getContentText());
  return;
}

function fixedEncodeURIComponent (str) {  
  // used to escape POST data
  return encodeURIComponent(str).replace(/!/g, '%21').replace(/'/g, '%27').  
    replace(/\(/g, '%28').replace(/\)/g, '%29').replace(/\*/g, '%2A');  
}
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What is the expected output? What do you see instead?

I expect that google sends both cookies to the redirected page, and then fetch()
returns the content of the redirected page (after successful the login).

Instead It seems that in the above example there is an infinite loop of redirects,
as the server doesn't receive the expected cookie (fyi - this is only my assumption).
Tests with another web login page produced the result "Your browser doesn't support cookies".


On which browser & OS?

Firefox 11 on Win XP.


Please provide any additional information below.

There's another problem with Cookies and redirects, filed as Issue 36755050: HTTPResponse.getAllHeaders() can't get Set-Cookie header in a response
which forwards to a new Location.
http://code.google.com/p/google-apps-script-issues/issues/detail?id=1253

In order to solve both problems, I suggest this very simple approach:
For the method UrlFetchApp.fetch(url, optAdvancedArgs), support an optional
boolean argument "ignoreLocation / dontFollowLocation / dontRedirect".
If provided, the fetch() function shall *not* perform a 2nd request to the redirected
Location:, and instead return the header of the 1st response. This way, the user
has access to all cookies and can request the forwarded page on his own.