backends: pass error logger to backends

internal/backend/cache/backend.go

@@ -2,9 +2,7 @@ package cache
 
 import (
 	"context"
-	"fmt"
 	"io"
-	"os"
 	"sync"
 
 	"github.com/restic/restic/internal/backend"
@@ -22,16 +20,18 @@ type Backend struct {
 	// is finished.
 	inProgressMutex sync.Mutex
 	inProgress      map[backend.Handle]chan struct{}
+	errorLog        func(string, ...interface{})
 }
 
 // ensure Backend implements backend.Backend
 var _ backend.Backend = &Backend{}
 
-func newBackend(be backend.Backend, c *Cache) *Backend {
+func newBackend(be backend.Backend, c *Cache, errorLog func(string, ...interface{})) *Backend {
 	return &Backend{
 		Backend:    be,
 		Cache:      c,
 		inProgress: make(map[backend.Handle]chan struct{}),
+		errorLog:   errorLog,
 	}
 }
 
@@ -253,7 +253,7 @@ func (b *Backend) List(ctx context.Context, t backend.FileType, fn func(f backen
 	// clear the cache for files that are not in the repo anymore, ignore errors
 	err = b.Cache.Clear(t, ids)
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "error clearing %s files in cache: %v\n", t.String(), err)
+		b.errorLog("error clearing %s files in cache: %v\n", t.String(), err)
 	}
 
 	return nil

internal/backend/cache/backend_test.go

@@ -67,7 +67,7 @@ func list(t testing.TB, be backend.Backend, fn func(backend.FileInfo) error) {
 func TestBackend(t *testing.T) {
 	be := mem.New()
 	c := TestNewCache(t)
-	wbe := c.Wrap(be)
+	wbe := c.Wrap(be, t.Logf)
 
 	h, data := randomData(5234142)
 
@@ -135,7 +135,7 @@ func (l *loadCountingBackend) Load(ctx context.Context, h backend.Handle, length
 func TestOutOfBoundsAccess(t *testing.T) {
 	be := &loadCountingBackend{Backend: mem.New()}
 	c := TestNewCache(t)
-	wbe := c.Wrap(be)
+	wbe := c.Wrap(be, t.Logf)
 
 	h, data := randomData(50)
 	save(t, be, h, data)
@@ -164,7 +164,7 @@ func TestOutOfBoundsAccess(t *testing.T) {
 func TestForget(t *testing.T) {
 	be := &loadCountingBackend{Backend: mem.New()}
 	c := TestNewCache(t)
-	wbe := c.Wrap(be)
+	wbe := c.Wrap(be, t.Logf)
 
 	h, data := randomData(50)
 	save(t, be, h, data)
@@ -236,7 +236,7 @@ func TestErrorBackend(t *testing.T) {
 		time.Sleep(time.Millisecond)
 	}
 
-	wrappedBE := c.Wrap(errBackend)
+	wrappedBE := c.Wrap(errBackend, t.Logf)
 	var wg sync.WaitGroup
 	for i := 0; i < 5; i++ {
 		wg.Add(1)
@@ -249,7 +249,7 @@ func TestErrorBackend(t *testing.T) {
 func TestAutomaticCacheClear(t *testing.T) {
 	be := mem.New()
 	c := TestNewCache(t)
-	wbe := c.Wrap(be)
+	wbe := c.Wrap(be, t.Logf)
 
 	// add two handles h1 and h2
 	h1, data := randomData(2000)
@@ -308,7 +308,7 @@ func TestAutomaticCacheClearInvalidFilename(t *testing.T) {
 	}
 	save(t, be, h, data)
 
-	wbe := c.Wrap(be)
+	wbe := c.Wrap(be, t.Logf)
 
 	// list all files in the backend
 	list(t, wbe, func(_ backend.FileInfo) error { return nil })

internal/backend/cache/cache.go

@@ -237,8 +237,8 @@ func IsOld(t time.Time, maxAge time.Duration) bool {
 }
 
 // Wrap returns a backend with a cache.
-func (c *Cache) Wrap(be backend.Backend) backend.Backend {
-	return newBackend(be, c)
+func (c *Cache) Wrap(be backend.Backend, errorLog func(string, ...interface{})) backend.Backend {
+	return newBackend(be, c, errorLog)
 }
 
 // BaseDir returns the base directory.