As I spent about four hours of playing Rumpelstiltskin because none of the typically very old code snippets for the old Spreadsheet versions and the old OAUTH you can find when googling "google docs script send excel attachment" or similar (i.e. you want to take an existing Spreadsheet, convert it to Excel format and send it as email attachment) actually worked, I finally found the solution.
To create the actual attachment content, neither the supposed res.getContent() nor res.getBlob() nor res.getBytes alone worked. These hints are misleading!
The only thing that works for me is response.getBlob().getContent()!
Whole code :
function sendCurrentDocAsEmail() {
var driveService = getDriveService();
var ssID = SpreadsheetApp.getActiveSpreadsheet().getId();
var sheetName = SpreadsheetApp.getActiveSpreadsheet().getName();
var email = "recipient@demo.com"
var subject = "Here be Subjects";
var body = "Don't even think about learning how to code. It's wasted time.";
var file = Drive.Files.get(ssID );
var url = file.exportLinks[MimeType.MICROSOFT_EXCEL];
var response = UrlFetchApp.fetch(url, {
headers: {
Authorization: 'Bearer ' + driveService.getAccessToken()
}
});
var attachments = [{
fileName:sheetName+".xlsx",
content: response.getBlob().getBytes(), // this single line has cost me hours!
mimeType:"application//xls",
headers: {
Authorization: 'Bearer ' + driveService.getAccessToken()
}
}];
MailApp.sendEmail(email,subject ,body, {attachments:attachments});
}
Where getDriveService() is a function from Google's "OAuth2 for Apps Script" readme on https://github.com/googlesamples/apps-script-oauth2
