azureblob: ignore directory markers in inital Fs creation too - fixes #2806

This is a follow-up to feea0532 including the initial Fs creation
where the backend detects whether the path is pointing to a file or a
directory.

backend/azureblob/azureblob.go

@@ -417,8 +417,8 @@ func NewFs(name, root string, m configmap.Mapper) (fs.Fs, error) {
 		}
 		_, err := f.NewObject(remote)
 		if err != nil {
-			if err == fs.ErrorObjectNotFound {
-				// File doesn't exist so return old f
+			if err == fs.ErrorObjectNotFound || err == fs.ErrorNotAFile {
+				// File doesn't exist or is a directory so return old f
 				f.root = oldRoot
 				return f, nil
 			}
@@ -474,6 +474,21 @@ func (o *Object) updateMetadataWithModTime(modTime time.Time) {
 	o.meta[modTimeKey] = modTime.Format(timeFormatOut)
 }
 
+// Returns whether file is a directory marker or not
+func isDirectoryMarker(size int64, metadata azblob.Metadata, remote string) bool {
+	// Directory markers are 0 length
+	if size == 0 {
+		// Note that metadata with hdi_isfolder = true seems to be a
+		// defacto standard for marking blobs as directories.
+		endsWithSlash := strings.HasSuffix(remote, "/")
+		if endsWithSlash || remote == "" || metadata["hdi_isfolder"] == "true" {
+			return true
+		}
+
+	}
+	return false
+}
+
 // listFn is called from list to handle an object
 type listFn func(remote string, object *azblob.BlobItem, isDirectory bool) error
 
@@ -539,26 +554,20 @@ func (f *Fs) list(dir string, recurse bool, maxResults uint, fn listFn) error {
 				continue
 			}
 			remote := file.Name[len(f.root):]
-			// is this a directory marker?
-			if *file.Properties.ContentLength == 0 {
-				// Note that metadata with hdi_isfolder = true seems to be a
-				// defacto standard for marking blobs as directories.
-				endsWithSlash := strings.HasSuffix(remote, "/")
-				if endsWithSlash || remote == "" || file.Metadata["hdi_isfolder"] == "true" {
-					if endsWithSlash {
-						remote = remote[:len(remote)-1]
-					}
-					err = fn(remote, file, true)
-					if err != nil {
-						return err
-					}
-					// Keep track of directory markers. If recursing then
-					// there will be no Prefixes so no need to keep track
-					if !recurse {
-						directoryMarkers[remote] = struct{}{}
-					}
-					continue // skip directory marker
+			if isDirectoryMarker(*file.Properties.ContentLength, file.Metadata, remote) {
+				if strings.HasSuffix(remote, "/") {
+					remote = remote[:len(remote)-1]
 				}
+				err = fn(remote, file, true)
+				if err != nil {
+					return err
+				}
+				// Keep track of directory markers. If recursing then
+				// there will be no Prefixes so no need to keep track
+				if !recurse {
+					directoryMarkers[remote] = struct{}{}
+				}
+				continue // skip directory marker
 			}
 			// Send object
 			err = fn(remote, file, false)
@@ -981,27 +990,37 @@ func (o *Object) setMetadata(metadata azblob.Metadata) {
 //  o.md5
 //  o.meta
 func (o *Object) decodeMetaDataFromPropertiesResponse(info *azblob.BlobGetPropertiesResponse) (err error) {
+	metadata := info.NewMetadata()
+	size := info.ContentLength()
+	if isDirectoryMarker(size, metadata, o.remote) {
+		return fs.ErrorNotAFile
+	}
 	// NOTE - Client library always returns MD5 as base64 decoded string, Object needs to maintain
 	// this as base64 encoded string.
 	o.md5 = base64.StdEncoding.EncodeToString(info.ContentMD5())
 	o.mimeType = info.ContentType()
-	o.size = info.ContentLength()
+	o.size = size
 	o.modTime = time.Time(info.LastModified())
 	o.accessTier = azblob.AccessTierType(info.AccessTier())
-	o.setMetadata(info.NewMetadata())
+	o.setMetadata(metadata)
 
 	return nil
 }
 
 func (o *Object) decodeMetaDataFromBlob(info *azblob.BlobItem) (err error) {
+	metadata := info.Metadata
+	size := *info.Properties.ContentLength
+	if isDirectoryMarker(size, metadata, o.remote) {
+		return fs.ErrorNotAFile
+	}
 	// NOTE - Client library always returns MD5 as base64 decoded string, Object needs to maintain
 	// this as base64 encoded string.
 	o.md5 = base64.StdEncoding.EncodeToString(info.Properties.ContentMD5)
 	o.mimeType = *info.Properties.ContentType
-	o.size = *info.Properties.ContentLength
+	o.size = size
 	o.modTime = info.Properties.LastModified
 	o.accessTier = info.Properties.AccessTier
-	o.setMetadata(info.Metadata)
+	o.setMetadata(metadata)
 	return nil
 }