onedrive: fix upload of zero length files #1716

Unfortunately multi part upload can't upload zero length files so
bring back the single part upload for zero length files only.

This was broken when we made all uploads multipart uploads.

backend/onedrive/onedrive.go

@@ -1112,7 +1112,7 @@ func (o *Object) createUploadSession(modTime time.Time) (response *api.CreateUpl
 }
 
 // uploadFragment uploads a part
-func (o *Object) uploadFragment(url string, start int64, totalSize int64, chunk io.ReadSeeker, chunkSize int64, info *api.Item) (err error) {
+func (o *Object) uploadFragment(url string, start int64, totalSize int64, chunk io.ReadSeeker, chunkSize int64) (info *api.Item, err error) {
 	opts := rest.Opts{
 		Method:        "PUT",
 		RootURL:       url,
@@ -1131,12 +1131,13 @@ func (o *Object) uploadFragment(url string, start int64, totalSize int64, chunk
 				// we are done :)
 				// read the item
 				defer fs.CheckClose(resp.Body, &err)
+				info = &api.Item{}
 				return false, json.NewDecoder(resp.Body).Decode(info)
 			}
 		}
 		return retry, err
 	})
-	return err
+	return info, err
 }
 
 // cancelUploadSession cancels an upload session
@@ -1155,16 +1156,16 @@ func (o *Object) cancelUploadSession(url string) (err error) {
 }
 
 // uploadMultipart uploads a file using multipart upload
-func (o *Object) uploadMultipart(in io.Reader, size int64, modTime time.Time, info *api.Item) (err error) {
+func (o *Object) uploadMultipart(in io.Reader, size int64, modTime time.Time) (info *api.Item, err error) {
 	if chunkSize%(320*1024) != 0 {
-		return errors.Errorf("chunk size %d is not a multiple of 320k", chunkSize)
+		return nil, errors.Errorf("chunk size %d is not a multiple of 320k", chunkSize)
 	}
 
 	// Create upload session
 	fs.Debugf(o, "Starting multipart upload")
 	session, err := o.createUploadSession(modTime)
 	if err != nil {
-		return err
+		return nil, err
 	}
 	uploadURL := session.UploadURL
 
@@ -1189,15 +1190,44 @@ func (o *Object) uploadMultipart(in io.Reader, size int64, modTime time.Time, in
 		}
 		seg := readers.NewRepeatableReader(io.LimitReader(in, n))
 		fs.Debugf(o, "Uploading segment %d/%d size %d", position, size, n)
-		err = o.uploadFragment(uploadURL, position, size, seg, n, info)
+		info, err = o.uploadFragment(uploadURL, position, size, seg, n)
 		if err != nil {
-			return err
+			return nil, err
 		}
 		remaining -= n
 		position += n
 	}
 
-	return nil
+	return info, nil
+}
+
+// uploadSinglepart uploads a file as a single part
+func (o *Object) uploadSinglepart(in io.Reader, size int64, modTime time.Time) (info *api.Item, err error) {
+	var resp *http.Response
+	opts := rest.Opts{
+		Method:        "PUT",
+		Path:          "/root:/" + rest.URLPathEscape(o.srvPath()) + ":/content",
+		ContentLength: &size,
+		Body:          in,
+	}
+	// for go1.8 (see release notes) we must nil the Body if we want a
+	// "Content-Length: 0" header which onedrive requires for all files.
+	if size == 0 {
+		opts.Body = nil
+	}
+	err = o.fs.pacer.CallNoRetry(func() (bool, error) {
+		resp, err = o.fs.srv.CallJSON(&opts, nil, &info)
+		return shouldRetry(resp, err)
+	})
+	if err != nil {
+		return nil, err
+	}
+	err = o.setMetaData(info)
+	if err != nil {
+		return nil, err
+	}
+	// Set the mod time now and read metadata
+	return o.setModTime(modTime)
 }
 
 // Update the object with the contents of the io.Reader, modTime and size
@@ -1210,8 +1240,13 @@ func (o *Object) Update(in io.Reader, src fs.ObjectInfo, options ...fs.OpenOptio
 	size := src.Size()
 	modTime := src.ModTime()
 
-	info := &api.Item{}
+	var info *api.Item
-	err = o.uploadMultipart(in, size, modTime, info)
+	if size <= 0 {
+		// This is for 0 length files, or files with an unknown size
+		info, err = o.uploadSinglepart(in, size, modTime)
+	} else {
+		info, err = o.uploadMultipart(in, size, modTime)
+	}
 	if err != nil {
 		return err
 	}