don't restore MemberInfo from RightPanel history when viewing a room

As bringing up a specific MemberInfo when you view a room is freaky,
even if it happened to be the last thing you were doing in that room.
Fixes element-hq/element-web#21487

src/components/structures/RightPanel.tsx

@@ -84,13 +84,30 @@ export default class RightPanel extends React.Component<IProps, IState> {
     public componentDidMount(): void {
         this.context.on(RoomStateEvent.Members, this.onRoomStateMember);
         RightPanelStore.instance.on(UPDATE_EVENT, this.onRightPanelStoreUpdate);
+
+        if (this.props.room?.roomId) {
+            // skip cards which are not to be restored from history
+            // (i.e. memberinfo cards which have already been viewed)
+            while (RightPanelStore.instance.currentCardForRoom(this.props.room.roomId)?.state.skipFromHistory) {
+                RightPanelStore.instance.popCard();
+            }
+        }
     }
 
     public componentWillUnmount(): void {
         this.context?.removeListener(RoomStateEvent.Members, this.onRoomStateMember);
         RightPanelStore.instance.off(UPDATE_EVENT, this.onRightPanelStoreUpdate);
     }
 
+    private static skipHistory(card: IRightPanelCard): boolean {
+        // determines phases whose history should not be persisted per-room
+        // so we don't find ourselves being teleported into random old MemberInfo
+        // views when viewing a given room.
+        // See https://github.com/vector-im/element-web/issues/21487
+        return (card.phase === RightPanelPhases.RoomMemberInfo ||
+                card.phase === RightPanelPhases.Room3pidMemberInfo);
+    }
+
     public static getDerivedStateFromProps(props: IProps): Partial<IState> {
         let currentCard: IRightPanelCard;
         if (props.room) {
@@ -100,6 +117,11 @@ export default class RightPanel extends React.Component<IProps, IState> {
             currentCard = RightPanelStore.instance.currentGroup;
         }
 
+        if (RightPanel.skipHistory(currentCard)) {
+            // having displayed this card, don't restore this card from history in future
+            RightPanelStore.instance.skipHistoryForCard(currentCard);
+        }
+
         if (currentCard?.phase && !RightPanelStore.instance.isPhaseValid(currentCard.phase, !!props.room)) {
             // XXX: We can probably get rid of this workaround once GroupView is dead, it's unmounting happens weirdly
             // late causing the app to soft-crash due to lack of a room object being passed to a RightPanel

src/stores/right-panel/RightPanelStore.ts

@@ -159,7 +159,7 @@ export default class RightPanelStore extends ReadyWatchingStore {
         if (!this.isPhaseValid(targetPhase)) return;
 
         if ((targetPhase === this.currentCardForRoom(rId)?.phase && !!cardState)) {
-            // Update state: set right panel with a new state but keep the phase (dont know it this is ever needed...)
+            // Update state: set right panel with a new state but keep the phase (don't know it this is ever needed...)
             const hist = this.byRoom[rId]?.history ?? [];
             hist[hist.length - 1].state = cardState;
             this.emitAndUpdateSettings();
@@ -214,6 +214,10 @@ export default class RightPanelStore extends ReadyWatchingStore {
         this.emitAndUpdateSettings();
     }
 
+    public skipHistoryForCard(card: IRightPanelCard) {
+        card.state.skipFromHistory = true;
+    }
+
     public popCard(roomId: string = null) {
         const rId = roomId ?? this.viewedRoomId;
         if (!this.byRoom[rId]) return;

src/stores/right-panel/RightPanelStoreIPanelState.ts

@@ -38,6 +38,8 @@ export interface IRightPanelCardState {
     threadHeadEvent?: MatrixEvent;
     initialEvent?: MatrixEvent;
     isInitialEventHighlighted?: boolean;
+    // should this card be skipped when switching to a room?
+    skipFromHistory?: boolean;
 }
 
 export interface IRightPanelCardStateStored {
@@ -54,6 +56,8 @@ export interface IRightPanelCardStateStored {
     threadHeadEventId?: string;
     initialEventId?: string;
     isInitialEventHighlighted?: boolean;
+    // should this card be skipped when switching to a room?
+    skipFromHistory?: boolean;
 }
 
 export interface IRightPanelCard {
@@ -104,6 +108,7 @@ export function convertCardToStore(panelState: IRightPanelCard): IRightPanelCard
             panelState.state.initialEvent.getId() : undefined,
         memberId: !!state?.member?.userId ?
             panelState.state.member.userId : undefined,
+        skipFromHistory: state.skipFromHistory,
     };
 
     return { state: stateStored, phase: panelState.phase };
@@ -125,6 +130,7 @@ function convertStoreToCard(panelStateStore: IRightPanelCardStored, room: Room):
             room.findEventById(stateStored.initialEventId) : undefined,
         member: !!stateStored?.memberId ?
             room.getMember(stateStored.memberId) : undefined,
+        skipFromHistory: stateStored.skipFromHistory,
     };
 
     return { state: state, phase: panelStateStore.phase };