Fix `getRelationsForEvent` under TypeScript `strict` mode (#9558)

* Fix getRelationsForEvent tsc strictness

* Use shared type for GetRelationsForEvent

* Fix lint

* Add alternative type

* getRelationsForEvent is not required

* Relations are optional

* Reactions are optional

* We expect relations in these tests

* Add more protection if the eventID is not defined

* Allow null too

* Better test typing

* User ID is not necessary unless something is selected

* It's okay to [].includes(null)

* Null is as good as undefined here

* Null or undefined is good here

* We have some expectations for the tests

* The room and user can be undefined too

* Protec

* Reactions are optional

* Try match signatures

* Null or undefined

* More null or undefined

* Protec

* Fix typo (wrong variable)

* Remove optional params

See https://github.com/matrix-org/matrix-react-sdk/pull/9558#discussion_r1017515913

* Fix up last maaaaybe relevant lint

Co-authored-by: Michael Telatynski <7t3chguy@gmail.com>

src/components/structures/MessagePanel.tsx

@@ -20,7 +20,6 @@ import classNames from 'classnames';
 import { Room } from 'matrix-js-sdk/src/models/room';
 import { EventType } from 'matrix-js-sdk/src/@types/event';
 import { MatrixEvent } from 'matrix-js-sdk/src/models/event';
-import { Relations } from "matrix-js-sdk/src/models/relations";
 import { logger } from 'matrix-js-sdk/src/logger';
 import { RoomStateEvent } from "matrix-js-sdk/src/models/room-state";
 import { M_BEACON_INFO } from 'matrix-js-sdk/src/@types/beacon';
@@ -35,7 +34,7 @@ import SettingsStore from '../../settings/SettingsStore';
 import RoomContext, { TimelineRenderingType } from "../../contexts/RoomContext";
 import { Layout } from "../../settings/enums/Layout";
 import { _t } from "../../languageHandler";
-import EventTile, { UnwrappedEventTile, IReadReceiptProps } from "../views/rooms/EventTile";
+import EventTile, { UnwrappedEventTile, GetRelationsForEvent, IReadReceiptProps } from "../views/rooms/EventTile";
 import { hasText } from "../../TextForEvent";
 import IRCTimelineProfileResizer from "../views/elements/IRCTimelineProfileResizer";
 import DMRoomMap from "../../utils/DMRoomMap";
@@ -186,7 +185,7 @@ interface IProps {
     // helper function to access relations for an event
     onUnfillRequest?(backwards: boolean, scrollToken: string): void;
 
-    getRelationsForEvent?(eventId: string, relationType: string, eventType: string): Relations;
+    getRelationsForEvent?: GetRelationsForEvent;
 
     hideThreadedMessages?: boolean;
     disableGrouping?: boolean;

src/components/structures/TimelinePanel.tsx

@@ -1714,7 +1714,7 @@ class TimelinePanel extends React.Component<IProps, IState> {
 
     private getRelationsForEvent = (
         eventId: string,
-        relationType: RelationType,
+        relationType: RelationType | string,
         eventType: EventType | string,
     ) => this.props.timelineSet.relations?.getChildEventsForEvent(eventId, relationType, eventType);
 

src/components/views/context_menus/MessageContextMenu.tsx

@@ -130,7 +130,7 @@ interface IProps extends IPosition {
     // True if the menu is being used as a right click menu
     rightClick?: boolean;
     // The Relations model from the JS SDK for reactions to `mxEvent`
-    reactions?: Relations;
+    reactions?: Relations | null | undefined;
     // A permalink to this event or an href of an anchor element the user has clicked
     link?: string;
 

src/components/views/dialogs/EndPollDialog.tsx

@@ -17,7 +17,6 @@ limitations under the License.
 import React from "react";
 import { MatrixEvent } from "matrix-js-sdk/src/models/event";
 import { MatrixClient } from "matrix-js-sdk/src/client";
-import { Relations } from "matrix-js-sdk/src/models/relations";
 import { PollEndEvent } from "matrix-events-sdk";
 
 import { _t } from "../../../languageHandler";
@@ -26,16 +25,13 @@ import QuestionDialog from "./QuestionDialog";
 import { findTopAnswer } from "../messages/MPollBody";
 import Modal from "../../../Modal";
 import ErrorDialog from "./ErrorDialog";
+import { GetRelationsForEvent } from "../rooms/EventTile";
 
 interface IProps extends IDialogProps {
     matrixClient: MatrixClient;
     event: MatrixEvent;
     onFinished: (success: boolean) => void;
-    getRelationsForEvent?: (
-        eventId: string,
-        relationType: string,
-        eventType: string
-    ) => Relations;
+    getRelationsForEvent?: GetRelationsForEvent;
 }
 
 export default class EndPollDialog extends React.Component<IProps> {

src/components/views/elements/ReplyChain.tsx

@@ -19,7 +19,6 @@ import React from 'react';
 import classNames from 'classnames';
 import { MatrixEvent } from 'matrix-js-sdk/src/models/event';
 import { Room } from 'matrix-js-sdk/src/models/room';
-import { Relations } from 'matrix-js-sdk/src/models/relations';
 import { MatrixClient } from 'matrix-js-sdk/src/client';
 
 import { _t } from '../../../languageHandler';
@@ -36,6 +35,7 @@ import AccessibleButton, { ButtonEvent } from './AccessibleButton';
 import { getParentEventId, shouldDisplayReply } from '../../../utils/Reply';
 import RoomContext from "../../../contexts/RoomContext";
 import { MatrixClientPeg } from '../../../MatrixClientPeg';
+import { GetRelationsForEvent } from "../rooms/EventTile";
 
 /**
  * This number is based on the previous behavior - if we have message of height
@@ -56,9 +56,7 @@ interface IProps {
     forExport?: boolean;
     isQuoteExpanded?: boolean;
     setQuoteExpanded: (isExpanded: boolean) => void;
-    getRelationsForEvent?: (
-        (eventId: string, relationType: string, eventType: string) => Relations
-    );
+    getRelationsForEvent?: GetRelationsForEvent;
 }
 
 interface IState {

src/components/views/emojipicker/ReactionPicker.tsx

@@ -29,7 +29,7 @@ import { FocusComposerPayload } from '../../../dispatcher/payloads/FocusComposer
 
 interface IProps {
     mxEvent: MatrixEvent;
-    reactions?: Relations;
+    reactions?: Relations | null | undefined;
     onFinished(): void;
 }
 

src/components/views/messages/IBodyProps.ts

@@ -16,11 +16,11 @@ limitations under the License.
 
 import React, { LegacyRef } from "react";
 import { MatrixEvent } from "matrix-js-sdk/src/models/event";
-import { Relations } from "matrix-js-sdk/src/models/relations";
 
 import { MediaEventHelper } from "../../../utils/MediaEventHelper";
 import EditorStateTransfer from "../../../utils/EditorStateTransfer";
 import { RoomPermalinkCreator } from "../../../utils/permalinks/Permalinks";
+import { GetRelationsForEvent } from "../rooms/EventTile";
 
 export interface IBodyProps {
     mxEvent: MatrixEvent;
@@ -52,7 +52,7 @@ export interface IBodyProps {
     isSeeingThroughMessageHiddenForModeration?: boolean;
 
     // helper function to access relations for this event
-    getRelationsForEvent?: (eventId: string, relationType: string, eventType: string) => Relations;
+    getRelationsForEvent?: GetRelationsForEvent;
 
     ref?: React.RefObject<any> | LegacyRef<any>;
 }

src/components/views/messages/MBeaconBody.tsx

@@ -101,8 +101,8 @@ const useUniqueId = (eventId: string): string => {
 // remove related beacon locations on beacon redaction
 const useHandleBeaconRedaction = (
     event: MatrixEvent,
-    getRelationsForEvent: GetRelationsForEvent,
-    cli: MatrixClient,
+    matrixClient: MatrixClient,
+    getRelationsForEvent?: GetRelationsForEvent,
 ): void => {
     const onBeforeBeaconInfoRedaction = useCallback((_event: MatrixEvent, redactionEvent: MatrixEvent) => {
         const relations = getRelationsForEvent ?
@@ -110,14 +110,14 @@ const useHandleBeaconRedaction = (
             undefined;
 
         relations?.getRelations()?.forEach(locationEvent => {
-            cli.redactEvent(
+            matrixClient.redactEvent(
                 locationEvent.getRoomId(),
                 locationEvent.getId(),
                 undefined,
                 redactionEvent.getContent(),
             );
         });
-    }, [event, getRelationsForEvent, cli]);
+    }, [event, matrixClient, getRelationsForEvent]);
 
     useEffect(() => {
         event.addListener(MatrixEventEvent.BeforeRedaction, onBeforeBeaconInfoRedaction);
@@ -151,7 +151,7 @@ const MBeaconBody: React.FC<IBodyProps> = React.forwardRef(({ mxEvent, getRelati
     const markerRoomMember = isSelfLocation(mxEvent.getContent()) ? mxEvent.sender : undefined;
     const isOwnBeacon = beacon?.beaconInfoOwner === matrixClient.getUserId();
 
-    useHandleBeaconRedaction(mxEvent, getRelationsForEvent, matrixClient);
+    useHandleBeaconRedaction(mxEvent, matrixClient, getRelationsForEvent);
 
     const onClick = () => {
         if (displayStatus !== BeaconDisplayStatus.Active) {

src/components/views/messages/MPollBody.tsx

@@ -16,6 +16,7 @@ limitations under the License.
 
 import React from 'react';
 import classNames from 'classnames';
+import { logger } from "matrix-js-sdk/src/logger";
 import { MatrixEvent, MatrixEventEvent } from "matrix-js-sdk/src/models/event";
 import { Relations, RelationsEvent } from 'matrix-js-sdk/src/models/relations';
 import { MatrixClient } from 'matrix-js-sdk/src/matrix';
@@ -43,49 +44,59 @@ import PollCreateDialog from "../elements/PollCreateDialog";
 import { MatrixClientPeg } from "../../../MatrixClientPeg";
 
 interface IState {
-    selected?: string; // Which option was clicked by the local user
+    selected?: string | null | undefined; // Which option was clicked by the local user
     voteRelations: RelatedRelations; // Voting (response) events
     endRelations: RelatedRelations; // Poll end events
 }
 
 export function createVoteRelations(
-    getRelationsForEvent: (
-        eventId: string,
-        relationType: string,
-        eventType: string
-    ) => Relations,
+    getRelationsForEvent: GetRelationsForEvent,
     eventId: string,
 ) {
-    return new RelatedRelations([
-        getRelationsForEvent(
-            eventId,
-            "m.reference",
-            M_POLL_RESPONSE.name,
-        ),
-        getRelationsForEvent(
-            eventId,
-            "m.reference",
-            M_POLL_RESPONSE.altName,
-        ),
-    ]);
+    const relationsList: Relations[] = [];
+
+    const pollResponseRelations = getRelationsForEvent(
+        eventId,
+        "m.reference",
+        M_POLL_RESPONSE.name,
+    );
+    if (pollResponseRelations) {
+        relationsList.push(pollResponseRelations);
+    }
+
+    const pollResposnseAltRelations = getRelationsForEvent(
+        eventId,
+        "m.reference",
+        M_POLL_RESPONSE.altName,
+    );
+    if (pollResposnseAltRelations) {
+        relationsList.push(pollResposnseAltRelations);
+    }
+
+    return new RelatedRelations(relationsList);
 }
 
 export function findTopAnswer(
     pollEvent: MatrixEvent,
     matrixClient: MatrixClient,
-    getRelationsForEvent?: (
-        eventId: string,
-        relationType: string,
-        eventType: string
-    ) => Relations,
+    getRelationsForEvent?: GetRelationsForEvent,
 ): string {
     if (!getRelationsForEvent) {
         return "";
     }
 
+    const pollEventId = pollEvent.getId();
+    if (!pollEventId) {
+        logger.warn(
+            "findTopAnswer: Poll event needs an event ID to fetch relations in order to determine " +
+            "the top answer - assuming no best answer",
+        );
+        return "";
+    }
+
     const poll = pollEvent.unstableExtensibleEvent as PollStartEvent;
     if (!poll?.isEquivalentTo(M_POLL_START)) {
-        console.warn("Failed to parse poll to determine top answer - assuming no best answer");
+        logger.warn("Failed to parse poll to determine top answer - assuming no best answer");
         return "";
     }
 
@@ -93,25 +104,32 @@ export function findTopAnswer(
         return poll.answers.find(a => a.id === answerId)?.text ?? "";
     };
 
-    const voteRelations = createVoteRelations(getRelationsForEvent, pollEvent.getId());
+    const voteRelations = createVoteRelations(getRelationsForEvent, pollEventId);
 
-    const endRelations = new RelatedRelations([
-        getRelationsForEvent(
-            pollEvent.getId(),
-            "m.reference",
-            M_POLL_END.name,
-        ),
-        getRelationsForEvent(
-            pollEvent.getId(),
-            "m.reference",
-            M_POLL_END.altName,
-        ),
-    ]);
+    const relationsList: Relations[] = [];
+
+    const pollEndRelations = getRelationsForEvent(
+        pollEventId,
+        "m.reference",
+        M_POLL_END.name,
+    );
+    if (pollEndRelations) {
+        relationsList.push(pollEndRelations);
+    }
+
+    const pollEndAltRelations = getRelationsForEvent(
+        pollEventId,
+        "m.reference",
+        M_POLL_END.altName,
+    );
+    if (pollEndAltRelations) {
+        relationsList.push(pollEndAltRelations);
+    }
+
+    const endRelations = new RelatedRelations(relationsList);
 
     const userVotes: Map<string, UserVote> = collectUserVotes(
         allVotes(pollEvent, matrixClient, voteRelations, endRelations),
-        matrixClient.getUserId(),
-        null,
     );
 
     const votes: Map<string, number> = countVotes(userVotes, poll);
@@ -132,36 +150,60 @@ export function findTopAnswer(
 export function isPollEnded(
     pollEvent: MatrixEvent,
     matrixClient: MatrixClient,
-    getRelationsForEvent?: (
-        eventId: string,
-        relationType: string,
-        eventType: string
-    ) => Relations,
+    getRelationsForEvent?: GetRelationsForEvent,
 ): boolean {
     if (!getRelationsForEvent) {
         return false;
     }
 
-    const roomCurrentState = matrixClient.getRoom(pollEvent.getRoomId()).currentState;
+    const pollEventId = pollEvent.getId();
+    if (!pollEventId) {
+        logger.warn(
+            "isPollEnded: Poll event must have event ID in order to determine whether it has ended " +
+            "- assuming poll has not ended",
+        );
+        return false;
+    }
+
+    const roomId = pollEvent.getRoomId();
+    if (!roomId) {
+        logger.warn(
+            "isPollEnded: Poll event must have room ID in order to determine whether it has ended " +
+            "- assuming poll has not ended",
+        );
+        return false;
+    }
+
+    const roomCurrentState = matrixClient.getRoom(roomId)?.currentState;
     function userCanRedact(endEvent: MatrixEvent) {
-        return roomCurrentState.maySendRedactionForEvent(
+        const endEventSender = endEvent.getSender();
+        return endEventSender && roomCurrentState && roomCurrentState.maySendRedactionForEvent(
             pollEvent,
-            endEvent.getSender(),
+            endEventSender,
         );
     }
 
-    const endRelations = new RelatedRelations([
-        getRelationsForEvent(
-            pollEvent.getId(),
-            "m.reference",
-            M_POLL_END.name,
-        ),
-        getRelationsForEvent(
-            pollEvent.getId(),
-            "m.reference",
-            M_POLL_END.altName,
-        ),
-    ]);
+    const relationsList: Relations[] = [];
+
+    const pollEndRelations = getRelationsForEvent(
+        pollEventId,
+        "m.reference",
+        M_POLL_END.name,
+    );
+    if (pollEndRelations) {
+        relationsList.push(pollEndRelations);
+    }
+
+    const pollEndAltRelations = getRelationsForEvent(
+        pollEventId,
+        "m.reference",
+        M_POLL_END.altName,
+    );
+    if (pollEndAltRelations) {
+        relationsList.push(pollEndAltRelations);
+    }
+
+    const endRelations = new RelatedRelations(relationsList);
 
     if (!endRelations) {
         return false;
@@ -175,7 +217,10 @@ export function isPollEnded(
 export function pollAlreadyHasVotes(mxEvent: MatrixEvent, getRelationsForEvent?: GetRelationsForEvent): boolean {
     if (!getRelationsForEvent) return false;
 
-    const voteRelations = createVoteRelations(getRelationsForEvent, mxEvent.getId());
+    const eventId = mxEvent.getId();
+    if (!eventId) return false;
+
+    const voteRelations = createVoteRelations(getRelationsForEvent, eventId);
     return voteRelations.getRelations().length > 0;
 }
 
@@ -335,18 +380,35 @@ export default class MPollBody extends React.Component<IBodyProps, IState> {
 
     private fetchRelations(eventType: NamespacedValue<string, string>): RelatedRelations | null {
         if (this.props.getRelationsForEvent) {
-            return new RelatedRelations([
-                this.props.getRelationsForEvent(
-                    this.props.mxEvent.getId(),
-                    "m.reference",
-                    eventType.name,
-                ),
-                this.props.getRelationsForEvent(
-                    this.props.mxEvent.getId(),
+            const relationsList: Relations[] = [];
+
+            const eventId = this.props.mxEvent.getId();
+            if (!eventId) {
+                return null;
+            }
+
+            const relations = this.props.getRelationsForEvent(
+                eventId,
+                "m.reference",
+                eventType.name,
+            );
+            if (relations) {
+                relationsList.push(relations);
+            }
+
+            // If there is an alternatve experimental event type, also look for that
+            if (eventType.altName) {
+                const altRelations = this.props.getRelationsForEvent(
+                    eventId,
                     "m.reference",
                     eventType.altName,
-                ),
-            ]);
+                );
+                if (altRelations) {
+                    relationsList.push(altRelations);
+                }
+            }
+
+            return new RelatedRelations(relationsList);
         } else {
             return null;
         }
@@ -380,7 +442,7 @@ export default class MPollBody extends React.Component<IBodyProps, IState> {
         const newEvents: MatrixEvent[] = this.state.voteRelations.getRelations()
             .filter(isPollResponse)
             .filter((mxEvent: MatrixEvent) =>
-                !this.seenEventIds.includes(mxEvent.getId()));
+                !this.seenEventIds.includes(mxEvent.getId()!));
         let newSelected = this.state.selected;
 
         if (newEvents.length > 0) {
@@ -422,7 +484,7 @@ export default class MPollBody extends React.Component<IBodyProps, IState> {
         const totalVotes = this.totalVotes(votes);
         const winCount = Math.max(...votes.values());
         const userId = this.context.getUserId();
-        const myVote = userVotes.get(userId)?.answers[0];
+        const myVote = userVotes?.get(userId!)?.answers[0];
         const disclosed = M_POLL_KIND_DISCLOSED.matches(poll.kind.name);
 
         // Disclosed: votes are hidden until I vote or the poll ends
@@ -655,12 +717,16 @@ function isPollResponse(responseEvent: MatrixEvent): boolean {
 
 /**
  * Figure out the correct vote for each user.
+ * @param userResponses current vote responses in the poll
+ * @param {string?} userId The userId for which the `selected` option will apply to.
+ *                  Should be set to the current user ID.
+ * @param {string?} selected Local echo selected option for the userId
  * @returns a Map of user ID to their vote info
  */
 function collectUserVotes(
     userResponses: Array<UserVote>,
-    userId: string,
-    selected?: string,
+    userId?: string | null | undefined,
+    selected?: string | null | undefined,
 ): Map<string, UserVote> {
     const userVotes: Map<string, UserVote> = new Map();
 
@@ -671,7 +737,7 @@ function collectUserVotes(
         }
     }
 
-    if (selected) {
+    if (selected && userId) {
         userVotes.set(userId, new UserVote(0, userId, [selected]));
     }
 

src/components/views/messages/MessageActionBar.tsx

@@ -59,6 +59,7 @@ import { Action } from '../../../dispatcher/actions';
 import SdkConfig from "../../../SdkConfig";
 import { ShowThreadPayload } from "../../../dispatcher/payloads/ShowThreadPayload";
 import useFavouriteMessages from '../../../hooks/useFavouriteMessages';
+import { GetRelationsForEvent } from '../rooms/EventTile';
 
 interface IOptionsButtonProps {
     mxEvent: MatrixEvent;
@@ -67,11 +68,7 @@ interface IOptionsButtonProps {
     getReplyChain: () => ReplyChain;
     permalinkCreator: RoomPermalinkCreator;
     onFocusChange: (menuDisplayed: boolean) => void;
-    getRelationsForEvent?: (
-        eventId: string,
-        relationType: string,
-        eventType: string
-    ) => Relations;
+    getRelationsForEvent?: GetRelationsForEvent;
 }
 
 const OptionsButton: React.FC<IOptionsButtonProps> = ({
@@ -135,7 +132,7 @@ const OptionsButton: React.FC<IOptionsButtonProps> = ({
 
 interface IReactButtonProps {
     mxEvent: MatrixEvent;
-    reactions: Relations;
+    reactions?: Relations | null | undefined;
     onFocusChange: (menuDisplayed: boolean) => void;
 }
 
@@ -299,7 +296,7 @@ const FavouriteButton = ({ mxEvent }: IFavouriteButtonProp) => {
 
 interface IMessageActionBarProps {
     mxEvent: MatrixEvent;
-    reactions?: Relations;
+    reactions?: Relations | null | undefined;
     // TODO: Types
     getTile: () => any | null;
     getReplyChain: () => ReplyChain | undefined;
@@ -307,11 +304,7 @@ interface IMessageActionBarProps {
     onFocusChange?: (menuDisplayed: boolean) => void;
     toggleThreadExpanded: () => void;
     isQuoteExpanded?: boolean;
-    getRelationsForEvent?: (
-        eventId: string,
-        relationType: RelationType | string,
-        eventType: string
-    ) => Relations;
+    getRelationsForEvent?: GetRelationsForEvent;
 }
 
 export default class MessageActionBar extends React.PureComponent<IMessageActionBarProps> {

src/components/views/messages/MessageEvent.tsx

@@ -16,7 +16,6 @@ limitations under the License.
 
 import React, { createRef } from 'react';
 import { EventType, MsgType } from "matrix-js-sdk/src/@types/event";
-import { Relations } from 'matrix-js-sdk/src/models/relations';
 import { M_BEACON_INFO } from 'matrix-js-sdk/src/@types/beacon';
 import { M_LOCATION } from 'matrix-js-sdk/src/@types/location';
 import { M_POLL_START } from "matrix-events-sdk";
@@ -41,7 +40,7 @@ import MPollBody from "./MPollBody";
 import MLocationBody from "./MLocationBody";
 import MjolnirBody from "./MjolnirBody";
 import MBeaconBody from "./MBeaconBody";
-import { IEventTileOps } from "../rooms/EventTile";
+import { GetRelationsForEvent, IEventTileOps } from "../rooms/EventTile";
 import { VoiceBroadcastBody, VoiceBroadcastInfoEventType, VoiceBroadcastInfoState } from '../../../voice-broadcast';
 
 // onMessageAllowed is handled internally
@@ -51,7 +50,7 @@ interface IProps extends Omit<IBodyProps, "onMessageAllowed" | "mediaEventHelper
     overrideEventTypes?: Record<string, typeof React.Component>;
 
     // helper function to access relations for this event
-    getRelationsForEvent?: (eventId: string, relationType: string, eventType: string) => Relations;
+    getRelationsForEvent?: GetRelationsForEvent;
 
     isSeeingThroughMessageHiddenForModeration?: boolean;
 }

src/components/views/messages/ReactionsRow.tsx

@@ -65,7 +65,7 @@ interface IProps {
     // The event we're displaying reactions for
     mxEvent: MatrixEvent;
     // The Relations model from the JS SDK for reactions to `mxEvent`
-    reactions?: Relations;
+    reactions?: Relations | null | undefined;
 }
 
 interface IState {
@@ -114,7 +114,7 @@ export default class ReactionsRow extends React.PureComponent<IProps, IState> {
     }
 
     componentDidUpdate(prevProps: IProps) {
-        if (prevProps.reactions !== this.props.reactions) {
+        if (this.props.reactions && prevProps.reactions !== this.props.reactions) {
             this.props.reactions.on(RelationsEvent.Add, this.onReactionsChange);
             this.props.reactions.on(RelationsEvent.Remove, this.onReactionsChange);
             this.props.reactions.on(RelationsEvent.Redaction, this.onReactionsChange);

src/components/views/rooms/EventTile.tsx

@@ -17,7 +17,7 @@ limitations under the License.
 
 import React, { createRef, forwardRef, MouseEvent, RefObject } from 'react';
 import classNames from "classnames";
-import { EventType, MsgType } from "matrix-js-sdk/src/@types/event";
+import { EventType, MsgType, RelationType } from "matrix-js-sdk/src/@types/event";
 import { EventStatus, MatrixEvent, MatrixEventEvent } from "matrix-js-sdk/src/models/event";
 import { Relations } from "matrix-js-sdk/src/models/relations";
 import { RoomMember } from "matrix-js-sdk/src/models/room-member";
@@ -87,7 +87,11 @@ import { isLocalRoom } from '../../../utils/localRoom/isLocalRoom';
 import { ElementCall } from "../../../models/Call";
 import { UnreadNotificationBadge } from './NotificationBadge/UnreadNotificationBadge';
 
-export type GetRelationsForEvent = (eventId: string, relationType: string, eventType: string) => Relations;
+export type GetRelationsForEvent = (
+    eventId: string,
+    relationType: RelationType | string,
+    eventType: EventType | string,
+) => Relations | null | undefined;
 
 // Our component structure for EventTiles on the timeline is:
 //
@@ -233,7 +237,7 @@ interface IState {
     // Whether onRequestKeysClick has been called since mounting.
     previouslyRequestedKeys: boolean;
     // The Relations model from the JS SDK for reactions to `mxEvent`
-    reactions: Relations;
+    reactions?: Relations | null | undefined;
 
     hover: boolean;
 

src/components/views/rooms/ReplyTile.tsx

@@ -19,7 +19,6 @@ import classNames from 'classnames';
 import { MatrixEvent, MatrixEventEvent } from "matrix-js-sdk/src/models/event";
 import { EventType, MsgType } from 'matrix-js-sdk/src/@types/event';
 import { logger } from "matrix-js-sdk/src/logger";
-import { Relations } from 'matrix-js-sdk/src/models/relations';
 
 import { _t } from '../../../languageHandler';
 import dis from '../../../dispatcher/dispatcher';
@@ -33,6 +32,7 @@ import MFileBody from "../messages/MFileBody";
 import MVoiceMessageBody from "../messages/MVoiceMessageBody";
 import { ViewRoomPayload } from "../../../dispatcher/payloads/ViewRoomPayload";
 import { renderReplyTile } from "../../../events/EventTileFactory";
+import { GetRelationsForEvent } from "../rooms/EventTile";
 
 interface IProps {
     mxEvent: MatrixEvent;
@@ -41,9 +41,7 @@ interface IProps {
     highlightLink?: string;
     onHeightChanged?(): void;
     toggleExpandedQuote?: () => void;
-    getRelationsForEvent?: (
-        (eventId: string, relationType: string, eventType: string) => Relations
-    );
+    getRelationsForEvent?: GetRelationsForEvent;
 }
 
 export default class ReplyTile extends React.PureComponent<IProps> {

test/components/views/messages/MPollBody-test.tsx

@@ -321,12 +321,13 @@ describe("MPollBody", () => {
         const votes = [responseEvent("@me:example.com", "pizza", 100)];
         const body = newMPollBody(votes);
         const props: IBodyProps = body.instance().props as IBodyProps;
-        const voteRelations: Relations = props.getRelationsForEvent(
+        const voteRelations = props!.getRelationsForEvent!(
             "$mypoll", "m.reference", M_POLL_RESPONSE.name);
+        expect(voteRelations).toBeDefined();
         clickRadio(body, "pizza");
 
         // When a new vote from me comes in
-        voteRelations.addEvent(responseEvent("@me:example.com", "wings", 101));
+        voteRelations!.addEvent(responseEvent("@me:example.com", "wings", 101));
 
         // Then the new vote is counted, not the old one
         expect(votesCount(body, "pizza")).toBe("0 votes");
@@ -342,12 +343,13 @@ describe("MPollBody", () => {
         const votes = [responseEvent("@me:example.com", "pizza")];
         const body = newMPollBody(votes);
         const props: IBodyProps = body.instance().props as IBodyProps;
-        const voteRelations: Relations = props.getRelationsForEvent(
+        const voteRelations = props!.getRelationsForEvent!(
             "$mypoll", "m.reference", M_POLL_RESPONSE.name);
+        expect(voteRelations).toBeDefined();
         clickRadio(body, "pizza");
 
         // When a new vote from someone else comes in
-        voteRelations.addEvent(responseEvent("@xx:example.com", "wings", 101));
+        voteRelations!.addEvent(responseEvent("@xx:example.com", "wings", 101));
 
         // Then my vote is still for pizza
         // NOTE: the new event does not affect the counts for other people -