fix(protocol): be more stringent about blocks in non-file entries (#10737)

Directories, but also symlinks, should not have blocks or a size.

Signed-off-by: Jakob Borg <jakob@kastelo.net>

lib/protocol/protocol.go

@@ -75,7 +75,8 @@ var (
 	errInvalidFilename  = errors.New("filename is invalid")
 	errUncleanFilename  = errors.New("filename not in canonical format")
 	errDeletedHasBlocks = errors.New("deleted file with non-empty block list")
-	errDirectoryHasBlocks = errors.New("directory with non-empty block list")
+	errNonFileHasBlocks = errors.New("non-file type with non-empty block list")
+	errNonFileHasSize   = errors.New("non-file type with nonzero size")
 	errFileHasNoBlocks  = errors.New("file with empty block list")
 )
 
@@ -635,9 +636,13 @@ func checkFileInfoConsistency(f FileInfo) error {
 		// Deleted files should have no blocks
 		return errDeletedHasBlocks
 
-	case f.Type == FileInfoTypeDirectory && len(f.Blocks) != 0:
+	case f.Type != FileInfoTypeFile && len(f.Blocks) != 0:
-		// Directories should have no blocks
+		// Only files should have blocks
-		return errDirectoryHasBlocks
+		return errNonFileHasBlocks
+
+	case f.Type != FileInfoTypeFile && f.Size != 0:
+		// Only files should have a size
+		return errNonFileHasSize
 
 	case !f.Deleted && !f.IsInvalid() && f.Type == FileInfoTypeFile && len(f.Blocks) == 0:
 		// Non-deleted, non-invalid files should have at least one block