Failure in Fetching Google Script's URL - google-apps-script

Question

URL: https://script.google.com/a/macros/MyDomain.com/s/MyProjectId/exec
To trigger the doGet() inside my Google Script, with URL:
Success: Manually Input above Url in the browser.
Failure: Fetch by Google Script UrlFetchApp.fetch(URL)
Is Fetch by program not allowed for Google Script's URL? Or have I made any stupid mistake?
I have tried to fetch by post method also to test doPost(), but got same result.
N.B.I have added my domain & script.google.com into APIs & auth/Push, and handled OAuth. No more authorization popup. So suppose not these issues.
~~~~~~~~~~~~~~~~~~~~~~~~~
Some people say this problem come from Google Apps's security in front of doGet() & doPost(). But after testing, it is failure no matter I run it on personal Gmail account or Google Apps account, and no matter run it as Developer, Domain users or Anonymous Anyone. Below is the demo code, without including the lengthy standard authorization code.
var REDIRECT_URL = 'https://script.google.com/macros/s/.../exec';
var SysEmail = "EmailAddress";
function doGet(e) {
MailApp.sendEmail(SysEmail, 'Test', 'doGet has received Push Notification');
}
//Running below function should trigger above doGet() theoretically, but not actually.
function TestGetByManual(){
var payload =
{
"kind" : "Test",
};
var options =
{
"method" : "get",
"followRedirects" : true,
"payload" : payload
};
var vResult = UrlFetchApp.fetch(REDIRECT_URL, options);
//vResult is Google's Login page.
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
After latest testings, I find that Google behave like this:
Since Google's security is so strong, setting parameter "followRedirects" to true is helpless. When Fetch meet Google before doGet() or doPost(), it will be stopped due to Authority reviewing. If it is fetched by manual (e.g. users' installation through browser), an authorization window will be pop-up (esp. if doGet() include authorization code inside). But if it is fetched by another App like my case, everything seems stop and doGet() and its authorization code will never be called!
The only workaround is: If I can set the App to execute as me and accessible by Anonymous, then there will be no Authority checking and everything go directly. Unluckily, even ignoring security issue, only personal Gmail account can make this setting. I, using Google Apps account, cannot make this "Anonymous" setting.
If authorization code will be called, I think there is still hope. But if my testing result is correct and no authorization code will be called before stop, I believe it is a dead corner.
The case here is still better. If the caller is not a controllable custom function, but an uncontrollable system function like Drive.changes.watch(), everything will be further helpless. (See my another post, which is my ultimate goal: Use Google Script's Web App as Webhook to receive Push Notification directly)
If any senior here can contact Google's Arun Nagarajan, really please help get a confirmation from him.

Answer 1

Works fine for me with the following code:
var REDIRECT_URL = 'https://script.google.com/macros/s/AKf.../exec';
var SysEmail = "anemail";
function doGet(e) {
MailApp.sendEmail(SysEmail, 'Test', 'doGet has received Push Notification');
}
function TestGetByManual(){
var vResult = UrlFetchApp.fetch(REDIRECT_URL);
Logger.log(vResult);
}
Make sure you save a new version and re-publish the webapp with that version and using the correct published url.