Don't create fictitious presence entries for users that don't have any

syncapi/storage/postgres/presence_table.go

@@ -127,6 +127,9 @@ func (p *presenceStatements) GetPresenceForUser(
 	}
 	stmt := sqlutil.TxStmt(txn, p.selectPresenceForUsersStmt)
 	err := stmt.QueryRowContext(ctx, userID).Scan(&result.Presence, &result.ClientFields.StatusMsg, &result.LastActiveTS)
+	if err == sql.ErrNoRows {
+		return nil, nil
+	}
 	result.ClientFields.Presence = result.Presence.String()
 	return result, err
 }

syncapi/storage/sqlite3/presence_table.go

@@ -142,6 +142,9 @@ func (p *presenceStatements) GetPresenceForUser(
 	}
 	stmt := sqlutil.TxStmt(txn, p.selectPresenceForUsersStmt)
 	err := stmt.QueryRowContext(ctx, userID).Scan(&result.Presence, &result.ClientFields.StatusMsg, &result.LastActiveTS)
+	if err == sql.ErrNoRows {
+		return nil, nil
+	}
 	result.ClientFields.Presence = result.Presence.String()
 	return result, err
 }

syncapi/streams/stream_presence.go

@@ -16,7 +16,6 @@ package streams
 
 import (
 	"context"
-	"database/sql"
 	"encoding/json"
 	"sync"
 
@@ -80,11 +79,10 @@ func (p *PresenceStreamProvider) IncrementalSync(
 				if _, ok := presences[roomUsers[i]]; ok {
 					continue
 				}
+				// Bear in mind that this might return nil, but at least populating
+				// a nil means that there's a map entry so we won't repeat this call.
 				presences[roomUsers[i]], err = p.DB.GetPresence(ctx, roomUsers[i])
 				if err != nil {
-					if err == sql.ErrNoRows {
-						continue
-					}
 					req.Log.WithError(err).Error("unable to query presence for user")
 					return from
 				}
@@ -93,8 +91,10 @@ func (p *PresenceStreamProvider) IncrementalSync(
 	}
 
 	lastPos := to
-	for i := range presences {
+	for _, presence := range presences {
-		presence := presences[i]
+		if presence == nil {
+			continue
+		}
 		// Ignore users we don't share a room with
 		if req.Device.UserID != presence.UserID && !p.notifier.IsSharedUser(req.Device.UserID, presence.UserID) {
 			continue

syncapi/sync/requestpool.go

@@ -127,14 +127,23 @@ func (rp *RequestPool) updatePresence(db storage.Presence, presence string, user
 	if !ok { // this should almost never happen
 		return
 	}
+
 	newPresence := types.PresenceInternal{
-		ClientFields: types.PresenceClientResponse{
-			Presence: presenceID.String(),
-		},
 		Presence:     presenceID,
 		UserID:       userID,
 		LastActiveTS: gomatrixserverlib.AsTimestamp(time.Now()),
 	}
+
+	// ensure we also send the current status_msg to federated servers and not nil
+	dbPresence, err := db.GetPresence(context.Background(), userID)
+	if err != nil && err != sql.ErrNoRows {
+		return
+	}
+	if dbPresence != nil {
+		newPresence.ClientFields = dbPresence.ClientFields
+	}
+	newPresence.ClientFields.Presence = presenceID.String()
+
 	defer rp.presence.Store(userID, newPresence)
 	// avoid spamming presence updates when syncing
 	existingPresence, ok := rp.presence.LoadOrStore(userID, newPresence)
@@ -145,13 +154,7 @@ func (rp *RequestPool) updatePresence(db storage.Presence, presence string, user
 		}
 	}
 
-	// ensure we also send the current status_msg to federated servers and not nil
+	if err := rp.producer.SendPresence(userID, presenceID, newPresence.ClientFields.StatusMsg); err != nil {
-	dbPresence, err := db.GetPresence(context.Background(), userID)
-	if err != nil && err != sql.ErrNoRows {
-		return
-	}
-
-	if err := rp.producer.SendPresence(userID, presenceID, dbPresence.ClientFields.StatusMsg); err != nil {
 		logrus.WithError(err).Error("Unable to publish presence message from sync")
 		return
 	}