oCIS FS: zero size file uploads create a blob entry in upload target

[wkloucek]

Describe the bug

Upload a zero size file to oCIS running on oCIS FS.

Steps to reproduce

Steps to reproduce the behavior:

1. Upload a zero size file using oC Web
2. Refresh the page

Expected behavior

You see exactly the file you uploaded

Actual behavior

You see the file you uploaded and a file with a UUIDv4.

Setup

oCIS master on e4cc2a5, but same behaviour was on oCIS 1.12.0

[C0rby]

Bug description

Here we check if the upload size is 0 bytes.
https://github.com/cs3org/reva/blob/582ce36aadccbc962ad01aebe2f0dcba7e790143/pkg/storage/utils/decomposedfs/upload.go#L300-L307

	if !info.SizeIsDeferred && info.Size == 0 {
		...
		err := u.FinishUpload(ctx) <-- Early finish
		...

If that is the case we finish the upload in line 303.

Now we get back to the ocdav handler:
https://github.com/cs3org/reva/blob/582ce36aadccbc962ad01aebe2f0dcba7e790143/internal/http/services/owncloud/ocdav/put.go#L222-L260

	uRes, err := client.InitiateFileUpload(ctx, uReq)
       ...
	httpReq, err := rhttp.NewRequest(ctx, http.MethodPut, ep, r.Body)
	...
	httpReq.Header.Set(datagateway.TokenTransportHeader, token)
	httpRes, err := s.client.Do(httpReq)

Even though the upload was finished already, the ocdav handler doesn't know this and continues with the simple dataprovider, which will eventually end up here:
https://github.com/cs3org/reva/blob/582ce36aadccbc962ad01aebe2f0dcba7e790143/pkg/storage/utils/decomposedfs/upload.go#L58-L72

	upload, err := fs.GetUpload(ctx, ref.GetPath()) <-- fail because no file in uploads directory
	if err != nil {
		// Upload corresponding to this ID was not found.
		...
		metadata := map[string]string{"sizedeferred": "true"}
		uploadIDs, err := fs.InitiateUpload(ctx, ref, 0, metadata) <-- Second initiate upload = UUID file
		...
		if upload, err = fs.GetUpload(ctx, uploadIDs["simple"]); err != nil {
		...

There it will try to get the upload and fail because we never wrote a .info file for the upload. Because of that it will create a new upload in line 65 and then continue to upload the file which we will see as the uuid file.

Possible Solution

We either need to remove the early finish in the NewUpload method or tell the webdav handler that the upload was already finished and not call the simple dataprovider.

[wkloucek]

oCDAV also has a special case for zero byte uploads
https://github.com/cs3org/reva/blob/master/internal/http/services/owncloud/ocdav/tus.go#L262

[nikslor]

Not sure if it's relevant; I think I also see this when using rclone to sync files to oCIS.