Remember the last used server for room directory searches

src/components/structures/RoomDirectory.tsx

@@ -48,6 +48,9 @@ import { ActionPayload } from "../../dispatcher/payloads";
 const MAX_NAME_LENGTH = 80;
 const MAX_TOPIC_LENGTH = 800;
 
+const LAST_SERVER_KEY = "mx_last_room_directory_server";
+const LAST_INSTANCE_KEY = "mx_last_room_directory_instance";
+
 function track(action: string) {
     Analytics.trackEvent('RoomDirectory', action);
 }
@@ -61,7 +64,7 @@ interface IState {
     loading: boolean;
     protocolsLoading: boolean;
     error?: string;
-    instanceId: string | symbol;
+    instanceId: string;
     roomServer: string;
     filterString: string;
     selectedCommunityId?: string;
@@ -116,6 +119,35 @@ export default class RoomDirectory extends React.Component<IProps, IState> {
         } else if (!selectedCommunityId) {
             MatrixClientPeg.get().getThirdpartyProtocols().then((response) => {
                 this.protocols = response;
+                const myHomeserver = MatrixClientPeg.getHomeserverName();
+                const lsRoomServer = localStorage.getItem(LAST_SERVER_KEY);
+                const lsInstanceId = localStorage.getItem(LAST_INSTANCE_KEY);
+                const roomServer = (
+                    SdkConfig.get().roomDirectory?.servers?.includes(lsRoomServer) ||
+                    SettingsStore.getValue("room_directory_servers")?.includes(lsRoomServer)
+                ) ? lsRoomServer : myHomeserver;
+
+                let instanceId: string = null;
+                if (
+                    (lsInstanceId === ALL_ROOMS) ||
+                    (
+                        roomServer === myHomeserver &&
+                        Object.values(this.protocols).some(p => p.instances.some(i => i.instance_id === lsInstanceId))
+                    )
+                ) {
+                    instanceId = lsInstanceId;
+                }
+
+                // Refresh the room list only if validation failed and we had to change these
+                if (this.state.instanceId !== instanceId || this.state.roomServer !== roomServer) {
+                    this.setState({
+                        protocolsLoading: false,
+                        instanceId,
+                        roomServer,
+                    });
+                    this.refreshRoomList();
+                    return;
+                }
                 this.setState({ protocolsLoading: false });
             }, (err) => {
                 console.warn(`error loading third party protocols: ${err}`);
@@ -150,8 +182,8 @@ export default class RoomDirectory extends React.Component<IProps, IState> {
             publicRooms: [],
             loading: true,
             error: null,
-            instanceId: undefined,
-            roomServer: MatrixClientPeg.getHomeserverName(),
+            instanceId: localStorage.getItem(LAST_INSTANCE_KEY),
+            roomServer: localStorage.getItem(LAST_SERVER_KEY),
             filterString: this.props.initialText || "",
             selectedCommunityId,
             communityName: null,
@@ -342,7 +374,7 @@ export default class RoomDirectory extends React.Component<IProps, IState> {
         }
     };
 
-    private onOptionChange = (server: string, instanceId?: string | symbol) => {
+    private onOptionChange = (server: string, instanceId?: string) => {
         // clear next batch so we don't try to load more rooms
         this.nextBatch = null;
         this.setState({
@@ -360,6 +392,14 @@ export default class RoomDirectory extends React.Component<IProps, IState> {
         // find the five gitter ones, at which point we do not want
         // to render all those rooms when switching back to 'all networks'.
         // Easiest to just blow away the state & re-fetch.
+
+        // We have to be careful here so that we don't set instanceId = "undefined"
+        localStorage.setItem(LAST_SERVER_KEY, server);
+        if (instanceId) {
+            localStorage.setItem(LAST_INSTANCE_KEY, instanceId);
+        } else {
+            localStorage.removeItem(LAST_INSTANCE_KEY);
+        }
     };
 
     private onFillRequest = (backwards: boolean) => {

src/components/views/directory/NetworkDropdown.tsx

@@ -41,7 +41,8 @@ import QuestionDialog from "../dialogs/QuestionDialog";
 import UIStore from "../../../stores/UIStore";
 import { compare } from "../../../utils/strings";
 
-export const ALL_ROOMS = Symbol("ALL_ROOMS");
+// XXX: We would ideally use a symbol here but we can't since we save this value to localStorage
+export const ALL_ROOMS = "ALL_ROOMS";
 
 const SETTING_NAME = "room_directory_servers";
 
@@ -94,8 +95,7 @@ export interface IInstance {
     fields: object;
     network_id: string;
     // XXX: this is undocumented but we rely on it.
-    // we inject a fake entry with a symbolic instance_id.
-    instance_id: string | symbol;
+    instance_id: string;
 }
 
 export interface IProtocol {
@@ -112,8 +112,8 @@ export type Protocols = Record<string, IProtocol>;
 interface IProps {
     protocols: Protocols;
     selectedServerName: string;
-    selectedInstanceId: string | symbol;
-    onOptionChange(server: string, instanceId?: string | symbol): void;
+    selectedInstanceId: string;
+    onOptionChange(server: string, instanceId?: string): void;
 }
 
 // This dropdown sources homeservers from three places:
@@ -171,7 +171,7 @@ const NetworkDropdown = ({ onOptionChange, protocols = {}, selectedServerName, s
 
             const protocolsList = server === hsName ? Object.values(protocols) : [];
             if (protocolsList.length > 0) {
-                // add a fake protocol with the ALL_ROOMS symbol
+                // add a fake protocol with ALL_ROOMS
                 protocolsList.push({
                     instances: [{
                         fields: [],