channels: drop stale membership caches on join/leave

After channels.leaveChannel, a client that polls channels.getFullChannel kept
receiving a projection that still showed it as an active member (left=false)
until the per-(viewer,channel) RPC projection cache and the store-level member
cache lapsed on their own or the async read-model NOTIFY landed. The client
therefore kept an open compose box while every send was already rejected with
CHANNEL_PRIVATE - most visible on public forum supergroups, where getFullChannel
keeps succeeding via the preview path instead of tearing the chat down.

Every other membership-mutating path already busts these caches synchronously;
join/leave/invite/request-approval did not. Add:

- store: invalidateChannelMembershipCaches (row + member + dialog caches),
  called post-commit from JoinChannel, LeaveChannel, ImportInvite,
  InviteToChannel.
- rpc: invalidateChannelMembershipProjection (channelFullProjectionCache pair),
  called from the join/leave/invite/hide-requests handlers for every user whose
  membership changed.

internal/rpc/channels_leave_rpc_test.go

@@ -109,6 +109,60 @@ func TestMessagesGetFutureChatCreatorAfterLeaveAndCreatorLeaveTransfers(t *testi
 	}
 }
 
+func TestLeaveChannelInvalidatesStaleFullChannelProjection(t *testing.T) {
+	ctx := context.Background()
+	userStore := memory.NewUserStore()
+	owner, _ := userStore.Create(ctx, domain.User{AccessHash: 9401, Phone: "15550009401", FirstName: "Owner"})
+	member, _ := userStore.Create(ctx, domain.User{AccessHash: 9402, Phone: "15550009402", FirstName: "Member"})
+	channelStore := memory.NewChannelStore()
+	channelService := appchannels.NewService(channelStore)
+	r := New(Config{}, Deps{
+		Users:    appusers.NewService(userStore),
+		Channels: channelService,
+	}, zaptest.NewLogger(t), fixedClock{now: time.Unix(1700009400, 0)})
+	created, err := channelService.CreateChannel(ctx, owner.ID, domain.CreateChannelRequest{
+		CreatorUserID: owner.ID,
+		Title:         "leave projection",
+		Megagroup:     true,
+		Date:          1700009400,
+	})
+	if err != nil {
+		t.Fatalf("create channel: %v", err)
+	}
+	if _, err := channelService.UpdateUsername(ctx, owner.ID, domain.UpdateChannelUsernameRequest{
+		ChannelID: created.Channel.ID,
+		Username:  "leave_projection_pub",
+	}); err != nil {
+		t.Fatalf("publish channel: %v", err)
+	}
+	inputChannel := &tg.InputChannel{ChannelID: created.Channel.ID, AccessHash: created.Channel.AccessHash}
+
+	if _, err := r.onChannelsJoinChannel(WithUserID(ctx, member.ID), inputChannel); err != nil {
+		t.Fatalf("member joins: %v", err)
+	}
+	// Warm the channels.getFullChannel projection cache while still a member.
+	full, err := r.onChannelsGetFullChannel(WithUserID(ctx, member.ID), inputChannel)
+	if err != nil {
+		t.Fatalf("full channel while joined: %v", err)
+	}
+	if chat, ok := full.Chats[0].(*tg.Channel); !ok || chat.Left {
+		t.Fatalf("joined full chat = %#v, want member (not left)", full.Chats[0])
+	}
+
+	if _, err := r.onChannelsLeaveChannel(WithUserID(ctx, member.ID), inputChannel); err != nil {
+		t.Fatalf("member leaves: %v", err)
+	}
+
+	after, err := r.onChannelsGetFullChannel(WithUserID(ctx, member.ID), inputChannel)
+	if err != nil {
+		t.Fatalf("full channel after leave: %v", err)
+	}
+	chat, ok := after.Chats[0].(*tg.Channel)
+	if !ok || !chat.Left {
+		t.Fatalf("post-leave full chat = %#v, want left=true (stale projection served)", after.Chats[0])
+	}
+}
+
 func TestMessagesEditChatCreatorTransfersWithoutChannelPts(t *testing.T) {
 	ctx := context.Background()
 	userStore := memory.NewUserStore()

internal/rpc/channels_members.go

@@ -341,6 +341,7 @@ func (r *Router) onChannelsInviteToChannel(ctx context.Context, req *tg.Channels
 		return nil, channelInviteErr(err)
 	}
 	r.invalidateChannelFullBotInfoCacheForChannel(res.Channel.ID)
+	r.invalidateChannelMembershipProjection(res.Channel.ID, channelMemberUserIDs(res.Members))
 	r.addOnlineChannelMemberships(res.Channel.ID, channelMemberUserIDs(res.Members)...)
 	cache := newViewerPeerCache(r)
 	updates := r.channelOperationUpdatesWithPeerCache(ctx, userID, res, cache)
@@ -379,6 +380,7 @@ func (r *Router) onChannelsJoinChannel(ctx context.Context, input tg.InputChanne
 		return nil, channelInviteErr(err)
 	}
 	r.invalidateChannelFullBotInfoCacheForChannel(res.Channel.ID)
+	r.invalidateChannelMembershipProjection(res.Channel.ID, channelMemberUserIDs(res.Members))
 	r.addOnlineChannelMemberships(res.Channel.ID, channelMemberUserIDs(res.Members)...)
 	updates := r.channelOperationUpdates(ctx, userID, res)
 	r.pushChannelUpdates(ctx, userID, res.Channel.ID, res.Recipients, func(viewerUserID int64) *tg.Updates {
@@ -406,6 +408,11 @@ func (r *Router) onChannelsLeaveChannel(ctx context.Context, input tg.InputChann
 		return nil, channelAdminErr(err)
 	}
 	r.invalidateChannelFullBotInfoCacheForChannel(res.Channel.ID)
+	membershipChanged := channelMemberUserIDs(res.Members)
+	if len(membershipChanged) == 0 {
+		membershipChanged = []int64{userID}
+	}
+	r.invalidateChannelMembershipProjection(res.Channel.ID, membershipChanged)
 	r.removeOnlineChannelMemberships(res.Channel.ID, userID)
 	r.recordChannelStateForUser(ctx, userID, res.Channel.ID, true)
 	updates := r.channelOperationUpdates(ctx, userID, res)
@@ -658,6 +665,7 @@ func (r *Router) onMessagesHideChatJoinRequest(ctx context.Context, req *tg.Mess
 		return nil, channelInviteErr(err)
 	}
 	r.invalidateChannelFullBotInfoCacheForChannel(res.Channel.ID)
+	r.invalidateChannelMembershipProjection(res.Channel.ID, channelMemberUserIDs(res.Members))
 	r.addOnlineChannelMemberships(res.Channel.ID, channelMemberUserIDs(res.Members)...)
 	updates := r.channelOperationUpdates(ctx, userID, res)
 	r.appendPendingJoinRequestsUpdate(ctx, userID, updates, res.Channel)
@@ -696,6 +704,7 @@ func (r *Router) onMessagesHideAllChatJoinRequests(ctx context.Context, req *tg.
 		return nil, channelInviteErr(err)
 	}
 	r.invalidateChannelFullBotInfoCacheForChannel(res.Channel.ID)
+	r.invalidateChannelMembershipProjection(res.Channel.ID, channelMemberUserIDs(res.Members))
 	r.addOnlineChannelMemberships(res.Channel.ID, channelMemberUserIDs(res.Members)...)
 	updates := r.channelOperationUpdates(ctx, userID, res)
 	r.appendPendingJoinRequestsUpdate(ctx, userID, updates, res.Channel)

internal/rpc/rpc_projection_cache.go

@@ -290,6 +290,24 @@ func (r *Router) invalidateRPCProjectionForPeer(ownerUserID int64, peer domain.P
 	}
 }
 
+// invalidateChannelMembershipProjection drops the cached channels.getFullChannel
+// projection for each user whose membership in channelID just changed (join,
+// leave, invite, request approval). Without it a client that polls
+// channels.getFullChannel right after channels.leaveChannel keeps getting a
+// projection that still shows it as an active member (left=false) until the
+// entry's TTL lapses, so it keeps an open compose box even though sends are
+// already rejected with CHANNEL_PRIVATE.
+func (r *Router) invalidateChannelMembershipProjection(channelID int64, userIDs []int64) {
+	if r.channelFullProjectionCache == nil || channelID == 0 {
+		return
+	}
+	for _, userID := range userIDs {
+		if userID != 0 {
+			r.channelFullProjectionCache.DeletePair(userID, channelID)
+		}
+	}
+}
+
 func (r *Router) invalidateRPCProjectionForChannel(channelID int64) {
 	if r.channelFullProjectionCache != nil {
 		r.channelFullProjectionCache.DeleteChannel(channelID)

internal/store/postgres/channel_invite_import.go

@@ -103,6 +103,7 @@ func (s *ChannelStore) ImportInvite(ctx context.Context, req domain.ImportChanne
 		return domain.CreateChannelResult{}, fmt.Errorf("commit import channel invite: %w", err)
 	}
 	committed = true
+	s.invalidateChannelMembershipCaches(result.Channel.ID, req.UserID)
 	recipients, _ := s.ListActiveChannelMemberIDs(ctx, req.UserID, result.Channel.ID, 0)
 	result.Recipients = recipients
 	return result, nil

internal/store/postgres/channel_invite_members.go

@@ -125,6 +125,7 @@ func (s *ChannelStore) InviteToChannel(ctx context.Context, channelID, inviterUs
 		return domain.CreateChannelResult{}, fmt.Errorf("commit invite channel: %w", err)
 	}
 	committed = true
+	s.invalidateChannelMembershipCaches(channelID, invitedIDs...)
 	recipients, _ := s.ListActiveChannelMemberIDs(ctx, inviterUserID, channelID, 0)
 	return domain.CreateChannelResult{Channel: channel, Members: members, Message: msg, Event: event, Recipients: recipients}, nil
 }

internal/store/postgres/channel_member_join.go

@@ -130,6 +130,7 @@ WHERE channel_id = $1 AND user_id = $2`, channelID, userID, member.ReadInboxMaxI
 		return domain.CreateChannelResult{}, fmt.Errorf("commit join channel: %w", err)
 	}
 	committed = true
+	s.invalidateChannelMembershipCaches(channelID, userID)
 	recipients, _ := s.ListActiveChannelMemberIDs(ctx, userID, channelID, 0)
 	return domain.CreateChannelResult{Channel: channel, Members: []domain.ChannelMember{member}, Message: msg, Event: event, Recipients: recipients}, nil
 }
@@ -259,6 +260,11 @@ WHERE id = $1`, channelID, channel.CreatorUserID, adminsDelta); err != nil {
 		return domain.CreateChannelResult{}, fmt.Errorf("commit leave channel: %w", err)
 	}
 	committed = true
+	leftUserIDs := make([]int64, 0, len(members))
+	for _, m := range members {
+		leftUserIDs = append(leftUserIDs, m.UserID)
+	}
+	s.invalidateChannelMembershipCaches(channelID, leftUserIDs...)
 	recipients = append(recipients, userID)
 	return domain.CreateChannelResult{Channel: channel, Members: members, Message: msg, Event: event, Recipients: recipients}, nil
 }

internal/store/postgres/channel_store.go

@@ -95,6 +95,33 @@ func (s *ChannelStore) boostCacheActive(db sqlcgen.DBTX) bool {
 	return s.boostCache != nil && db == s.db
 }
 
+// invalidateChannelMembershipCaches drops the in-process reads that a membership
+// change (join, leave, invite, kick) makes stale for the given users. The
+// ReadModelChangeListener also clears these off the async NOTIFY, but callers
+// must not depend on that round-trip: a client that polls channels.getFullChannel
+// right after channels.leaveChannel would otherwise keep seeing itself as an
+// active member (and keep an open compose box) until the notify lands. Call it
+// post-commit.
+func (s *ChannelStore) invalidateChannelMembershipCaches(channelID int64, userIDs ...int64) {
+	if channelID == 0 {
+		return
+	}
+	if s.rowCache != nil {
+		s.rowCache.delete(channelID)
+	}
+	for _, userID := range userIDs {
+		if userID == 0 {
+			continue
+		}
+		if s.memberCache != nil {
+			s.memberCache.delete(channelID, userID)
+		}
+		if s.dialogCache != nil {
+			s.dialogCache.delete(userID, channelID)
+		}
+	}
+}
+
 // NewChannelStore 基于 pgx 连接池（或事务）创建 ChannelStore。
 func NewChannelStore(db sqlcgen.DBTX, opts ...ChannelStoreOption) *ChannelStore {
 	s := &ChannelStore{db: db}