Trouble attaching file to SendGrid email in Google Apps Script

Question

I've been consuming StackOverflow info for years now and have never posted, but I've finally found something that stumps me, and doesn't seem to have a direct response anywhere. I work in Google Apps Script, and have successfully integrated scripts with the SendGrid V3 Web API to send emails, including emails with attachments. But for some reason I can't get it to work with a PDF pulled from Google Drive. Here is how I'm creating the attachment:

var filePath = "https://drive.google.com/file/d/19rzCtnOMWw0ZZM4FViMWVZWkRRnsWx3L/view?usp=sharing";
var response = UrlFetchApp.fetch(filePath);
var attachment = Utilities.base64Encode(response.getContent());

... and here is the object I'm passing to the v3/mail/send endpoint:

"attachments": [{"content": attachment, "type": "application/pdf", "filename": "testPDF.pdf"}]

When I do this, I receive an email with a PDF attachment, and the attachment is the same size as the PDF file in Google Drive. But when I try to open it, I get an error telling me I can't preview the file, and telling me to try downloading it instead. When I download and open, I get an "Error: Failed to load PDF document" message. Clearly I'm somehow creating an attachment that is not a proper PDF document. Is there anything in the above that someone can spot that I'm doing wrong?

I'm self-taught and a bit of a hack, so I apologize in advance if I'm missing something obvious, or if I've excluded critical information.

Answer 1

• Use getBlob() instead of base64Encode(response.getContent())
• Use getAs(contentType)
• Pass a variable of requested type instead of an object as an attachment.

Working sample:

function myFunction() {
  var filePath = "https://drive.google.com/file/d/19rzCtnOMWw0ZZM4FViMWVZWkRRnsWx3L/view?usp=sharing";
  var response = UrlFetchApp.fetch(filePath);
  var attachment = response.getBlob().getAs(MimeType.PDF);
  attachment.setName("testPDF.pdf");
  GmailApp.sendEmail("recipient", "subject", "body", {"attachments": [attachment]})
}

Sidenote:

If the file is located on your Drive, you can make your request much easier, without UrlfetchApp:

function myFunction2() {
  GmailApp.sendEmail("recipient", "subject", "body", {
    "attachments": [ DriveApp.getFileById("19rzCtnOMWw0ZZM4FViMWVZWkRRnsWx3L").getAs(MimeType.PDF)]}
  )
}

Answer 2

Well, after much more digging, I found the answer I was looking for. What was initially so confusing to me was that I had successfully retrieved PDFs on the web and attached them to SendGrid messages using the same UrlFetchApp and base64encode pattern posted in my question. But through some other threads, I found out that UrlFetchApp doesn't work the same way with Google Drive files. After experimenting with the Drive API, I decided to look more closely at WHY the UrlFetchApp pattern was successful with "normal" URLs, and came to the conclusion that it was because the UrlFetchApp response has a method called "getContent()" that returns binary data. So I went back and looked at how to get binary data from a PDF stored on Google Drive, and came up with the below pattern:

  var docBytes = DriveApp.getFileById("19rzCtnOMWw0ZZM4FViMWVZWkRRnsWx3L").getBlob().getBytes();
  var doc = Utilities.base64Encode(docBytes);
  var attachments = [{"content": doc, "type": "application/pdf", "filename": docTitle}];  

I kept the call to the SendGrid endpoint v3/mail/send endpoint the same as before:

"attachments": [{"content": attachment, "type": "application/pdf", "filename": "testPDF.pdf"}]

... and now it works! Thank you again to ziganotschka for looking at this and giving me some clues to get me on the right track.