Use composition to expose UserPrincipalBackend in filesystemBackend.
That way, no need to re-define the CurrentUserPrincipal method.
---
 storage/filesystem.go | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/storage/filesystem.go b/storage/filesystem.go
index cd19f4d0a6c5..04e383df7562 100644
--- a/storage/filesystem.go
+++ b/storage/filesystem.go
@@ -26,10 +26,10 @@ import (
 )
 
 type filesystemBackend struct {
-	path                 string
-	caldavPrefix         string
-	carddavPrefix        string
-	userPrincipalBackend webdav.UserPrincipalBackend
+	webdav.UserPrincipalBackend
+	path          string
+	caldavPrefix  string
+	carddavPrefix string
 }
 
 var (
@@ -45,20 +45,16 @@ func NewFilesystem(fsPath, caldavPrefix, carddavPrefix string, userPrincipalBack
 		return nil, nil, fmt.Errorf("base path for filesystem backend must be a directory")
 	}
 	backend := &filesystemBackend{
+		UserPrincipalBackend: userPrincipalBackend,
 		path:                 fsPath,
 		caldavPrefix:         caldavPrefix,
 		carddavPrefix:        carddavPrefix,
-		userPrincipalBackend: userPrincipalBackend,
 	}
 	return backend, backend, nil
 }
 
-func (b *filesystemBackend) CurrentUserPrincipal(ctx context.Context) (string, error) {
-	return b.userPrincipalBackend.CurrentUserPrincipal(ctx)
-}
-
 func (b *filesystemBackend) AddressbookHomeSetPath(ctx context.Context) (string, error) {
-	upPath, err := b.userPrincipalBackend.CurrentUserPrincipal(ctx)
+	upPath, err := b.CurrentUserPrincipal(ctx)
 	if err != nil {
 		return "", err
 	}
@@ -67,7 +63,7 @@ func (b *filesystemBackend) AddressbookHomeSetPath(ctx context.Context) (string,
 }
 
 func (b *filesystemBackend) CalendarHomeSetPath(ctx context.Context) (string, error) {
-	upPath, err := b.userPrincipalBackend.CurrentUserPrincipal(ctx)
+	upPath, err := b.CurrentUserPrincipal(ctx)
 	if err != nil {
 		return "", err
 	}
-- 
2.36.1

From: Simon Ser <contact@emersion.fr>

Thanks!