repository: make reloading broken files explicit

internal/cache/backend.go

@@ -161,14 +161,10 @@ func (b *Backend) Load(ctx context.Context, h backend.Handle, length int, offset
 	// try loading from cache without checking that the handle is actually cached
 	inCache, err := b.loadFromCache(h, length, offset, consumer)
 	if inCache {
-		if err == nil {
-			return nil
-		}
-
-		// drop from cache and retry once
-		_ = b.Cache.remove(h)
+		debug.Log("error loading %v from cache: %v", h, err)
+		// the caller must explicitly use cache.Forget() to remove the cache entry
+		return err
 	}
-	debug.Log("error loading %v from cache: %v", h, err)
 
 	// if we don't automatically cache this file type, fall back to the backend
 	if !autoCacheTypes(h) {
@@ -184,6 +180,7 @@ func (b *Backend) Load(ctx context.Context, h backend.Handle, length int, offset
 
 	inCache, err = b.loadFromCache(h, length, offset, consumer)
 	if inCache {
+		debug.Log("error loading %v from cache: %v", h, err)
 		return err
 	}
 

internal/cache/file.go

@@ -55,14 +55,12 @@ func (c *Cache) load(h backend.Handle, length int, offset int64) (io.ReadCloser,
 	size := fi.Size()
 	if size <= int64(crypto.CiphertextLength(0)) {
 		_ = f.Close()
-		_ = c.remove(h)
-		return nil, errors.Errorf("cached file %v is truncated, removing", h)
+		return nil, errors.Errorf("cached file %v is truncated", h)
 	}
 
 	if size < offset+int64(length) {
 		_ = f.Close()
-		_ = c.remove(h)
-		return nil, errors.Errorf("cached file %v is too short, removing", h)
+		return nil, errors.Errorf("cached file %v is too short", h)
 	}
 
 	if offset > 0 {
@@ -139,6 +137,10 @@ func (c *Cache) save(h backend.Handle, rd io.Reader) error {
 	return errors.WithStack(err)
 }
 
+func (c *Cache) Forget(h backend.Handle) error {
+	return c.remove(h)
+}
+
 // remove deletes a file. When the file is not cached, no error is returned.
 func (c *Cache) remove(h backend.Handle) error {
 	if !c.canBeCached(h.Type) {