Google Apps Script: UrlFetchApp Post File - google-apps-script

Question

I'm trying to POST a file to a REST API via Google Apps Script. The idea is that I have a process that is creating copies of a Google Doc, and I want to be able to post those newly created Docs to a third party system.
I found in UrlFetchApp that I can send files. However, I'm having issues sending the correct header values.
My request looks like so:
var file = DriveApp.getFileById(fileId);
var body = {
"file": file.getAs(MimeType.PDF)
};
var headers = {
'Content-Disposition': 'attachment; filename="'+ file.getName() +'"',
'Content-Length': file.getSize()
};
My options when I call UrlFetchApp.fetch(url, options) looks like :
({
method:"POST",
headers:{
'Content-Disposition':"attachment; filename=\"My Merge Development_row_1.pdf\"",
'Content-Length':90665,
Authorization:"Bearer TOKEN"
},
contentType:"application/x-www-form-urlencoded",
muteHttpExceptions:true,
payload:{file:Blob}
})
The API that I'm sending the files to requires the 'Content-Length' header. But, when I try to set a value for 'Content-Length' header I get an Apps Script error, "Attribute provided with invalid value: Header:Content-Length". If I don't set the Content-Length header then the API responds that the Content-Length and file size don't match.
Any ideas on how I set the Content-Length header so I can POST the file?

Answer 1

There is an existing ticket highlighting that the documentation is not clear on this very issue
The solution is:
Move content length value from "content-Length" name/value pair in
headers to the advanced argument "contentLength"
So in your example your options should look like
({
method:"POST",
headers:{
'Content-Disposition':"attachment; filename=\"My Merge Development_row_1.pdf\"",
Authorization:"Bearer TOKEN"
},
contentLength: 90665,
contentType:"application/x-www-form-urlencoded",
muteHttpExceptions:true,
payload:{file:Blob}
})
EDIT: Added a full example function to get contentLength and blob shown below:
function testFilePost() {
var file = DriveApp.getFileById(doc_id).getAs(MimeType.PDF);
var headers = {
'Content-Disposition': 'attachment; filename="'+ file.getName() +'"',
};
var options =
{
"method" : "post",
"payload": file.getBytes(),
"headers": headers,
"contentLength": file.getBytes().length,
};
var result = JSON.parse(UrlFetchApp.fetch('http://httpbin.org/post', options).getContentText());
Logger.log(result);
}