fix(server): failed transcoded files should not be cached (#4124)

* Close stream on caching errors

* fix(test): replace errPartialReader with errFakeReader to fix lint error

Signed-off-by: Deluan <deluan@navidrome.org>

* fix(test): update error assertion to check for substring in closed file error

Signed-off-by: Deluan <deluan@navidrome.org>

---------

Signed-off-by: Deluan <deluan@navidrome.org>

utils/cache/file_caches.go

@@ -174,6 +174,7 @@ func (fc *fileCache) Get(ctx context.Context, arg Item) (*CachedStream, error) {
 		go func() {
 			if err := copyAndClose(w, reader); err != nil {
 				log.Debug(ctx, "Error storing file in cache", "cache", fc.name, "key", key, err)
+				_ = r.Close()
 				_ = fc.invalidate(ctx, key)
 			} else {
 				log.Trace(ctx, "File successfully stored in cache", "cache", fc.name, "key", key)

utils/cache/file_caches_test.go

@@ -116,18 +116,16 @@ var _ = Describe("File Caches", func() {
 				})
 			})
 			When("reader returns error", func() {
-				It("does not cache", func() {
+				It("does not cache and closes the stream", func() {
 					fc := callNewFileCache("test", "1KB", "test", 0, func(ctx context.Context, arg Item) (io.Reader, error) {
-						return errFakeReader{errors.New("read failure")}, nil
+						return &errFakeReader{data: []byte("data"), err: errors.New("read failure")}, nil
 					})
 
 					s, err := fc.Get(context.Background(), &testArg{"test"})
 					Expect(err).ToNot(HaveOccurred())
-					_, _ = io.Copy(io.Discard, s)
+					_, err = io.ReadAll(s)
-					// TODO How to make the fscache reader return the underlying reader error?
+					Expect(err.Error()).To(ContainSubstring("file already closed"))
-					//Expect(err).To(MatchError("read failure"))
 
-					// Data should not be cached (or eventually be removed from cache)
 					Eventually(func() bool {
 						s, _ = fc.Get(context.Background(), &testArg{"test"})
 						if s != nil {
@@ -145,6 +143,17 @@ type testArg struct{ s string }
 
 func (t *testArg) Key() string { return t.s }
 
-type errFakeReader struct{ err error }
+type errFakeReader struct {
+	data []byte
+	err  error
+	off  int
+}
 
-func (e errFakeReader) Read([]byte) (int, error) { return 0, e.err }
+func (e *errFakeReader) Read(b []byte) (int, error) {
+	if e.off < len(e.data) {
+		n := copy(b, e.data[e.off:])
+		e.off += n
+		return n, nil
+	}
+	return 0, e.err
+}