fix: preserve user context in async NowPlaying dispatch

Fixed issue #4787 where plugin scrobblers received an empty username during NowPlaying events. The async worker was passing context.Background() which lost all user information.

Changed nowPlayingEntry to store the full context (with cancellation removed via context.WithoutCancel) and pass it to dispatchNowPlaying. This ensures plugin scrobblers can extract username from the context for authorization checks.

Updated tests to verify username is properly propagated through the async workflow, matching the actual plugin adapter behavior of checking both request.UsernameFrom and request.UserFrom.

core/scrobbler/play_tracker.go

@@ -32,6 +32,7 @@ type Submission struct {
 }
 
 type nowPlayingEntry struct {
+	ctx      context.Context
 	userId   string
 	track    *model.MediaFile
 	position int
@@ -220,15 +221,17 @@ func (p *playTracker) NowPlaying(ctx context.Context, playerId string, playerNam
 	}
 	player, _ := request.PlayerFrom(ctx)
 	if player.ScrobbleEnabled {
-		p.enqueueNowPlaying(playerId, user.ID, mf, position)
+		p.enqueueNowPlaying(ctx, playerId, user.ID, mf, position)
 	}
 	return nil
 }
 
-func (p *playTracker) enqueueNowPlaying(playerId string, userId string, track *model.MediaFile, position int) {
+func (p *playTracker) enqueueNowPlaying(ctx context.Context, playerId string, userId string, track *model.MediaFile, position int) {
 	p.npMu.Lock()
 	defer p.npMu.Unlock()
+	ctx = context.WithoutCancel(ctx) // Prevent cancellation from affecting background processing
 	p.npQueue[playerId] = nowPlayingEntry{
+		ctx:      ctx,
 		userId:   userId,
 		track:    track,
 		position: position,
@@ -267,7 +270,7 @@ func (p *playTracker) nowPlayingWorker() {
 
 		// Process entries without holding lock
 		for _, entry := range entries {
-			p.dispatchNowPlaying(context.Background(), entry.userId, entry.track, entry.position)
+			p.dispatchNowPlaying(entry.ctx, entry.userId, entry.track, entry.position)
 		}
 	}
 }

core/scrobbler/play_tracker_test.go

@@ -170,6 +170,17 @@ var _ = Describe("PlayTracker", func() {
 			Expect(err).ToNot(HaveOccurred())
 			Expect(eventBroker.getEvents()).To(BeEmpty())
 		})
+
+		It("passes user to scrobbler via context (fix for issue #4787)", func() {
+			ctx = request.WithUser(ctx, model.User{ID: "u-1", UserName: "testuser"})
+			ctx = request.WithPlayer(ctx, model.Player{ScrobbleEnabled: true})
+
+			err := tracker.NowPlaying(ctx, "player-1", "player-one", "123", 0)
+			Expect(err).ToNot(HaveOccurred())
+			Eventually(func() bool { return fake.GetNowPlayingCalled() }).Should(BeTrue())
+			// Verify the username was passed through async dispatch via context
+			Eventually(func() string { return fake.GetUsername() }).Should(Equal("testuser"))
+		})
 	})
 
 	Describe("GetNowPlaying", func() {
@@ -428,6 +439,7 @@ type fakeScrobbler struct {
 	nowPlayingCalled atomic.Bool
 	ScrobbleCalled   atomic.Bool
 	userID           atomic.Pointer[string]
+	username         atomic.Pointer[string]
 	track            atomic.Pointer[model.MediaFile]
 	position         atomic.Int32
 	LastScrobble     atomic.Pointer[Scrobble]
@@ -453,6 +465,13 @@ func (f *fakeScrobbler) GetPosition() int {
 	return int(f.position.Load())
 }
 
+func (f *fakeScrobbler) GetUsername() string {
+	if p := f.username.Load(); p != nil {
+		return *p
+	}
+	return ""
+}
+
 func (f *fakeScrobbler) IsAuthorized(ctx context.Context, userId string) bool {
 	return f.Error == nil && f.Authorized
 }
@@ -463,6 +482,16 @@ func (f *fakeScrobbler) NowPlaying(ctx context.Context, userId string, track *mo
 		return f.Error
 	}
 	f.userID.Store(&userId)
+	// Capture username from context (this is what plugin scrobblers do)
+	username, _ := request.UsernameFrom(ctx)
+	if username == "" {
+		if u, ok := request.UserFrom(ctx); ok {
+			username = u.UserName
+		}
+	}
+	if username != "" {
+		f.username.Store(&username)
+	}
 	f.track.Store(track)
 	f.position.Store(int32(position))
 	return nil