make subscription handle return undefined, so we can reassign optional members in one statement

src/observable/BaseObservable.ts

@@ -14,6 +14,10 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+// we return undefined so you can reassign any member
+// that uses `member?: T` syntax in one statement.
+export type SubscriptionHandle = () => undefined;
+
 export abstract class BaseObservable<T> {
     protected _handlers: Set<T> = new Set<T>();
 
@@ -25,7 +29,7 @@ export abstract class BaseObservable<T> {
 
     }
 
-    subscribe(handler: T): () => void {
+    subscribe(handler: T): SubscriptionHandle {
         this._handlers.add(handler);
         if (this._handlers.size === 1) {
             this.onSubscribeFirst();
@@ -35,15 +39,14 @@ export abstract class BaseObservable<T> {
         };
     }
 
-    unsubscribe(handler: T | null): null {
+    unsubscribe(handler?: T): undefined {
         if (handler) {
             this._handlers.delete(handler);
             if (this._handlers.size === 0) {
                 this.onUnsubscribeLast();
             }
-            handler = null;
         }
-        return null;
+        return undefined;
     }
 
     unsubscribeAll(): void {

src/platform/web/ui/general/ListView.ts

@@ -16,6 +16,7 @@ limitations under the License.
 
 import {el} from "./html";
 import {mountView, insertAt} from "./utils";
+import {SubscriptionHandle} from "../../../../observable/BaseObservable";
 import {BaseObservableList as ObservableList} from "../../../../observable/list/BaseObservableList";
 import {IView, IMountArgs} from "./types";
 
@@ -27,8 +28,6 @@ interface IOptions<T, V> {
     parentProvidesUpdates?: boolean
 }
 
-type SubscriptionHandle = () => void;
-
 export class ListView<T, V extends IView> implements IView {
 
     private _onItemClick?: (childView: V, evt: UIEvent) => void;
@@ -115,8 +114,7 @@ export class ListView<T, V extends IView> implements IView {
     }
 
     private _unloadList() {
-        this._subscription!()
-        this._subscription = undefined;
+        this._subscription = this._subscription!();
         for (let child of this._childInstances!) {
             child.unmount();
         }

src/sdk.ts

@@ -0,0 +1,58 @@
+/*
+Copyright 2020 Bruno Windels <bruno@windels.cloud>
+Copyright 2020 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// import {RecordRequester, ReplayRequester} from "./matrix/net/request/replay.js";
+import {SessionContainer} from "./matrix/SessionContainer.js";
+import {RootViewModel} from "./domain/RootViewModel.js";
+import {createNavigation, createRouter} from "./domain/navigation/index.js";
+// Don't use a default export here, as we use multiple entries during legacy build,
+// which does not support default exports,
+// see https://github.com/rollup/plugins/tree/master/packages/multi-entry
+export async function main(platform) {
+    try {
+        // to replay:
+        // const fetchLog = await (await fetch("/fetchlogs/constrainterror.json")).json();
+        // const replay = new ReplayRequester(fetchLog, {delay: false});
+        // const request = replay.request;
+
+        // to record:
+        // const recorder = new RecordRequester(createFetchRequest(clock.createTimeout));
+        // const request = recorder.request;
+        // window.getBrawlFetchLog = () => recorder.log();
+        const navigation = createNavigation();
+        platform.setNavigation(navigation);
+        const urlRouter = createRouter({navigation, history: platform.history});
+        urlRouter.attach();
+        const olmPromise = platform.loadOlm();
+        const workerPromise = platform.loadOlmWorker();
+
+        const vm = new RootViewModel({
+            createSessionContainer: () => {
+                return new SessionContainer({platform, olmPromise, workerPromise});
+            },
+            platform,
+            // the only public interface of the router is to create urls,
+            // so we call it that in the view models
+            urlCreator: urlRouter,
+            navigation,
+        });
+        await vm.load();
+        platform.createAndMountRootView(vm);
+    } catch(err) {
+        console.error(`${err.message}:\n${err.stack}`);
+    }
+}