Merge pull request #793 from ibeckermayer/ibeckermayer/ts-conversion-observable-map

Typescript conversion for `src/observable/map`

.ts-eslintrc.js

@@ -20,6 +20,10 @@ module.exports = {
     rules: {
         "@typescript-eslint/no-floating-promises": 2,
         "@typescript-eslint/no-misused-promises": 2,
-        "semi": ["error", "always"]
+        "no-unused-vars": "off",
+        "@typescript-eslint/no-unused-vars": ["warn"],
+        "no-undef": "off",
+        "semi": ["error", "always"],
+        "@typescript-eslint/explicit-function-return-type": ["error"]
     }
 };

src/domain/SessionPickerViewModel.js

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {SortedArray} from "../observable/index.js";
+import {SortedArray} from "../observable";
 import {ViewModel} from "./ViewModel";
 import {avatarInitials, getIdentifierColorNumber} from "./avatar";
 

src/domain/session/leftpanel/LeftPanelViewModel.js

@@ -20,8 +20,8 @@ import {RoomTileViewModel} from "./RoomTileViewModel.js";
 import {InviteTileViewModel} from "./InviteTileViewModel.js";
 import {RoomBeingCreatedTileViewModel} from "./RoomBeingCreatedTileViewModel.js";
 import {RoomFilter} from "./RoomFilter.js";
-import {ApplyMap} from "../../../observable/map/ApplyMap.js";
+import {ApplyMap} from "../../../observable";
-import {addPanelIfNeeded} from "../../navigation/index";
+import {addPanelIfNeeded} from "../../navigation";
 
 export class LeftPanelViewModel extends ViewModel {
     constructor(options) {

src/domain/session/rightpanel/MemberListViewModel.js

@@ -46,8 +46,8 @@ export class MemberListViewModel extends ViewModel {
             const vm = new MemberTileViewModel(this.childOptions({member, emitChange, mediaRepository}));
             this.nameDisambiguator.disambiguate(vm);
             return vm;
-        }
+        };
-        const updater = (vm, params, newMember) => {
+        const updater = (params, vm, newMember) => {
             vm.updateFrom(newMember);
             this.nameDisambiguator.disambiguate(vm);
         };

src/domain/session/room/timeline/ReactionsViewModel.js

@@ -13,7 +13,7 @@ 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 {ObservableMap} from "../../../../observable/map/ObservableMap";
+import {ObservableMap} from "../../../../observable";
 
 export class ReactionsViewModel {
     constructor(parentTile) {

src/lib.ts

@@ -78,8 +78,7 @@ export {
     MappedList,
     AsyncMappedList,
     ConcatList,
-    ObservableMap
+} from "./observable";
-} from "./observable/index";
 export {
     BaseObservableValue,
     ObservableValue,

src/matrix/Session.js

@@ -21,7 +21,7 @@ import {RoomStatus} from "./room/common";
 import {RoomBeingCreated} from "./room/RoomBeingCreated";
 import {Invite} from "./room/Invite.js";
 import {Pusher} from "./push/Pusher";
-import { ObservableMap } from "../observable/index.js";
+import {ObservableMap} from "../observable";
 import {User} from "./User.js";
 import {DeviceMessageHandler} from "./DeviceMessageHandler.js";
 import {Account as E2EEAccount} from "./e2ee/Account.js";
@@ -192,7 +192,7 @@ export class Session {
     /**
      * Enable secret storage by providing the secret storage credential.
      * This will also see if there is a megolm key backup and try to enable that if so.
-     * 
+     *
      * @param  {string} type       either "passphrase" or "recoverykey"
      * @param  {string} credential either the passphrase or the recovery key, depending on the type
      * @return {Promise} resolves or rejects after having tried to enable secret storage
@@ -663,7 +663,7 @@ export class Session {
         if (this._e2eeAccount && deviceOneTimeKeysCount) {
             changes.e2eeAccountChanges = this._e2eeAccount.writeSync(deviceOneTimeKeysCount, txn, log);
         }
-    
+
         const deviceLists = syncResponse.device_lists;
         if (this._deviceTracker && Array.isArray(deviceLists?.changed) && deviceLists.changed.length) {
             await log.wrap("deviceLists", log => this._deviceTracker.writeDeviceChanges(deviceLists.changed, txn, log));
@@ -908,7 +908,7 @@ export class Session {
     Creates an empty (summary isn't loaded) the archived room if it isn't
     loaded already, assuming sync will either remove it (when rejoining) or
     write a full summary adopting it from the joined room when leaving
-    
+
     @internal
     */
     createOrGetArchivedRoomForSync(roomId) {

src/matrix/room/members/MemberList.js

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {ObservableMap} from "../../../observable/map/ObservableMap";
+import {ObservableMap} from "../../../observable";
 import {RetainedValue} from "../../../utils/RetainedValue";
 
 export class MemberList extends RetainedValue {

src/matrix/room/timeline/Timeline.js

@@ -15,7 +15,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {SortedArray, AsyncMappedList, ConcatList, ObservableArray} from "../../../observable/index.js";
+import {SortedArray, AsyncMappedList, ConcatList, ObservableArray} from "../../../observable";
 import {Disposables} from "../../../utils/Disposables";
 import {Direction} from "./Direction";
 import {TimelineReader} from "./persistence/TimelineReader.js";
@@ -45,7 +45,7 @@ export class Timeline {
         });
         this._readerRequest = null;
         this._allEntries = null;
-        /** Stores event entries that we had to fetch from hs/storage for reply previews (because they were not in timeline) */ 
+        /** Stores event entries that we had to fetch from hs/storage for reply previews (because they were not in timeline) */
         this._contextEntriesNotInTimeline = new Map();
         /** Only used to decrypt non-persisted context entries fetched from the homeserver */
         this._decryptEntries = null;
@@ -189,7 +189,7 @@ export class Timeline {
         // before it has any subscriptions, we bail out if this isn't
         // the case yet. This can happen when sync adds or replaces entries
         // before load has finished and the view has subscribed to the timeline.
-        // 
+        //
         // Once the subscription is setup, MappedList will set up the local
         // relations as needed with _applyAndEmitLocalRelationChange,
         // so we're not missing anything by bailing out.
@@ -239,7 +239,7 @@ export class Timeline {
                 if (err.name === "CompareError") {
                     // see FragmentIdComparer, if the replacing entry is on a fragment
                     // that is currently not loaded into the FragmentIdComparer, it will
-                    // throw a CompareError, and it means that the event is not loaded 
+                    // throw a CompareError, and it means that the event is not loaded
                     // in the timeline (like when receiving a relation for an event
                     // that is not loaded in memory) so we can just drop this error as
                     // replacing an event that is not already loaded is a no-op.
@@ -311,7 +311,7 @@ export class Timeline {
      * - timeline
      * - storage
      * - homeserver
-     * @param {EventEntry[]} entries 
+     * @param {EventEntry[]} entries
      */
     async _loadContextEntriesWhereNeeded(entries) {
         for (const entry of entries) {
@@ -392,7 +392,7 @@ export class Timeline {
      * [loadAtTop description]
      * @param  {[type]} amount [description]
      * @return {boolean} true if the top of the timeline has been reached
-     * 
+     *
      */
     async loadAtTop(amount) {
         if (this._disposables.isDisposed) {
@@ -547,7 +547,7 @@ export function tests() {
                 content: {},
                 relatedEventId: event2.event_id
             }}));
-            // 4. subscribe (it's now safe to iterate timeline.entries) 
+            // 4. subscribe (it's now safe to iterate timeline.entries)
             timeline.entries.subscribe(new ListObserver());
             // 5. check the local relation got correctly aggregated
             const locallyRedacted = await poll(() => Array.from(timeline.entries)[0].isRedacting);

src/observable/BaseObservable.ts

@@ -34,7 +34,7 @@ export abstract class BaseObservable<T> {
         if (this._handlers.size === 1) {
             this.onSubscribeFirst();
         }
-        return () => {
+        return (): undefined => {
             return this.unsubscribe(handler);
         };
     }
@@ -63,22 +63,23 @@ export abstract class BaseObservable<T> {
     // Add iterator over handlers here
 }
 
+// eslint-disable-next-line @typescript-eslint/explicit-function-return-type
 export function tests() {
     class Collection extends BaseObservable<{}> {
         firstSubscribeCalls: number = 0;
         firstUnsubscribeCalls: number = 0;
 
-        onSubscribeFirst() { this.firstSubscribeCalls += 1; }
+        onSubscribeFirst(): void { this.firstSubscribeCalls += 1; }
-        onUnsubscribeLast() { this.firstUnsubscribeCalls += 1; }
+        onUnsubscribeLast(): void { this.firstUnsubscribeCalls += 1; }
     }
 
     return {
-        test_unsubscribe(assert) {
+        test_unsubscribe(assert): void {
             const c = new Collection();
             const unsubscribe = c.subscribe({});
             unsubscribe();
             assert.equal(c.firstSubscribeCalls, 1);
             assert.equal(c.firstUnsubscribeCalls, 1);
         }
-    }
+    };
 }

src/observable/ObservableValue.ts

@@ -20,7 +20,7 @@ import type {SubscriptionHandle} from "./BaseObservable";
 
 // like an EventEmitter, but doesn't have an event type
 export abstract class BaseObservableValue<T> extends BaseObservable<(value: T) => void> {
-    emit(argument: T) {
+    emit(argument: T): void {
         for (const h of this._handlers) {
             h(argument);
         }
@@ -68,7 +68,7 @@ class WaitForHandle<T> implements IWaitHandle<T> {
         return this._promise;
     }
 
-    dispose() {
+    dispose(): void {
         if (this._subscription) {
             this._subscription();
             this._subscription = null;
@@ -82,7 +82,7 @@ class WaitForHandle<T> implements IWaitHandle<T> {
 
 class ResolvedWaitForHandle<T> implements IWaitHandle<T> {
     constructor(public promise: Promise<T>) {}
-    dispose() {}
+    dispose(): void {}
 }
 
 export class ObservableValue<T> extends BaseObservableValue<T> {
@@ -113,7 +113,7 @@ export class RetainedObservableValue<T> extends ObservableValue<T> {
         this._freeCallback = freeCallback;
     }
 
-    onUnsubscribeLast() {
+    onUnsubscribeLast(): void {
         super.onUnsubscribeLast();
         this._freeCallback();
     }
@@ -130,7 +130,7 @@ export class FlatMapObservableValue<P, C> extends BaseObservableValue<C | undefi
         super();
     }
 
-    onUnsubscribeLast() {
+    onUnsubscribeLast(): void {
         super.onUnsubscribeLast();
         this.sourceSubscription = this.sourceSubscription!();
         if (this.targetSubscription) {
@@ -138,7 +138,7 @@ export class FlatMapObservableValue<P, C> extends BaseObservableValue<C | undefi
         }
     }
 
-    onSubscribeFirst() {
+    onSubscribeFirst(): void {
         super.onSubscribeFirst();
         this.sourceSubscription = this.source.subscribe(() => {
             this.updateTargetSubscription();
@@ -147,7 +147,7 @@ export class FlatMapObservableValue<P, C> extends BaseObservableValue<C | undefi
         this.updateTargetSubscription();
     }
 
-    private updateTargetSubscription() {
+    private updateTargetSubscription(): void {
         const sourceValue = this.source.get();
         if (sourceValue) {
             const target = this.mapper(sourceValue);
@@ -174,9 +174,10 @@ export class FlatMapObservableValue<P, C> extends BaseObservableValue<C | undefi
     }
 }
 
+// eslint-disable-next-line @typescript-eslint/explicit-function-return-type
 export function tests() {
     return {
-        "set emits an update": assert => {
+        "set emits an update": (assert): void => {
             const a = new ObservableValue<number>(0);
             let fired = false;
             const subscription = a.subscribe(v => {
@@ -187,7 +188,7 @@ export function tests() {
             assert(fired);
             subscription();
         },
-        "set doesn't emit if value hasn't changed": assert => {
+        "set doesn't emit if value hasn't changed": (assert): void => {
             const a = new ObservableValue(5);
             let fired = false;
             const subscription = a.subscribe(() => {
@@ -198,24 +199,24 @@ export function tests() {
             assert(!fired);
             subscription();
         },
-        "waitFor promise resolves on matching update": async assert => {
+        "waitFor promise resolves on matching update": async (assert): Promise<void> => {
             const a = new ObservableValue(5);
             const handle = a.waitFor(v => v === 6);
-            Promise.resolve().then(() => {
+            await Promise.resolve().then(() => {
                 a.set(6);
             });
             await handle.promise;
             assert.strictEqual(a.get(), 6);
         },
-        "waitFor promise rejects when disposed": async assert => {
+        "waitFor promise rejects when disposed": async (assert): Promise<void> => {
             const a = new ObservableValue<number>(0);
             const handle = a.waitFor(() => false);
-            Promise.resolve().then(() => {
+            await Promise.resolve().then(() => {
                 handle.dispose();
             });
             await assert.rejects(handle.promise, AbortError);
         },
-        "flatMap.get": assert => {
+        "flatMap.get": (assert): void => {
             const a = new ObservableValue<undefined | {count: ObservableValue<number>}>(undefined);
             const countProxy = a.flatMap(a => a!.count);
             assert.strictEqual(countProxy.get(), undefined);
@@ -223,7 +224,7 @@ export function tests() {
             a.set({count});
             assert.strictEqual(countProxy.get(), 0);
         },
-        "flatMap update from source": assert => {
+        "flatMap update from source": (assert): void => {
             const a = new ObservableValue<undefined | {count: ObservableValue<number>}>(undefined);
             const updates: (number | undefined)[] = [];
             a.flatMap(a => a!.count).subscribe(count => {
@@ -233,7 +234,7 @@ export function tests() {
             a.set({count});
             assert.deepEqual(updates, [0]);
         },
-        "flatMap update from target": assert => {
+        "flatMap update from target": (assert): void => {
             const a = new ObservableValue<undefined | {count: ObservableValue<number>}>(undefined);
             const updates: (number | undefined)[] = [];
             a.flatMap(a => a!.count).subscribe(count => {
@@ -244,5 +245,5 @@ export function tests() {
             count.set(5);
             assert.deepEqual(updates, [0, 5]);
         }
-    }
+    };
 }

src/observable/index.js

@@ -1,48 +0,0 @@
-/*
-Copyright 2020 Bruno Windels <bruno@windels.cloud>
-
-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 {SortedMapList} from "./list/SortedMapList.js";
-import {FilteredMap} from "./map/FilteredMap.js";
-import {MappedMap} from "./map/MappedMap.js";
-import {JoinedMap} from "./map/JoinedMap.js";
-import {BaseObservableMap} from "./map/BaseObservableMap";
-// re-export "root" (of chain) collections
-export { ObservableArray } from "./list/ObservableArray";
-export { SortedArray } from "./list/SortedArray";
-export { MappedList } from "./list/MappedList";
-export { AsyncMappedList } from "./list/AsyncMappedList";
-export { ConcatList } from "./list/ConcatList";
-export { ObservableMap } from "./map/ObservableMap";
-
-// avoid circular dependency between these classes
-// and BaseObservableMap (as they extend it)
-Object.assign(BaseObservableMap.prototype, {
-    sortValues(comparator) {
-        return new SortedMapList(this, comparator);
-    },
-
-    mapValues(mapper, updater) {
-        return new MappedMap(this, mapper, updater);
-    },
-
-    filterValues(filter) {
-        return new FilteredMap(this, filter);
-    },
-
-    join(...otherMaps) {
-        return new JoinedMap([this].concat(otherMaps));
-    }
-});

src/observable/index.ts

@@ -0,0 +1,24 @@
+/*
+Copyright 2020 Bruno Windels <bruno@windels.cloud>
+
+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.
+*/
+
+
+// re-export "root" (of chain) collection
+export { ObservableMap, ApplyMap, FilteredMap, JoinedMap, LogMap, MappedMap } from "./map";
+export { ObservableArray } from "./list/ObservableArray";
+export { SortedArray } from "./list/SortedArray";
+export { MappedList } from "./list/MappedList";
+export { AsyncMappedList } from "./list/AsyncMappedList";
+export { ConcatList } from "./list/ConcatList";

src/observable/list/AsyncMappedList.ts

@@ -16,7 +16,7 @@ limitations under the License.
 */
 
 import {IListObserver} from "./BaseObservableList";
-import {BaseMappedList, Mapper, Updater, runAdd, runUpdate, runRemove, runMove, runReset} from "./BaseMappedList";
+import {BaseMappedList, runAdd, runUpdate, runRemove, runMove, runReset} from "./BaseMappedList";
 
 export class AsyncMappedList<F,T> extends BaseMappedList<F,T,Promise<T>> implements IListObserver<F> {
     private _eventQueue: AsyncEvent<F>[] | null = null;
@@ -31,7 +31,7 @@ export class AsyncMappedList<F,T> extends BaseMappedList<F,T,Promise<T>> impleme
             this._eventQueue.push(new AddEvent(idx, item));
             idx += 1;
         }
-        this._flush();
+        void this._flush();
     }
 
     async _flush(): Promise<void> {
@@ -52,35 +52,35 @@ export class AsyncMappedList<F,T> extends BaseMappedList<F,T,Promise<T>> impleme
     onReset(): void {
         if (this._eventQueue) {
             this._eventQueue.push(new ResetEvent());
-            this._flush();
+            void this._flush();
         }
     }
 
     onAdd(index: number, value: F): void {
         if (this._eventQueue) {
             this._eventQueue.push(new AddEvent(index, value));
-            this._flush();
+            void this._flush();
         }
     }
 
     onUpdate(index: number, value: F, params: any): void {
         if (this._eventQueue) {
             this._eventQueue.push(new UpdateEvent(index, value, params));
-            this._flush();
+            void this._flush();
         }
     }
 
     onRemove(index: number): void {
         if (this._eventQueue) {
             this._eventQueue.push(new RemoveEvent(index));
-            this._flush();
+            void this._flush();
         }
     }
 
     onMove(fromIdx: number, toIdx: number): void {
         if (this._eventQueue) {
             this._eventQueue.push(new MoveEvent(fromIdx, toIdx));
-            this._flush();
+            void this._flush();
         }
     }
 
@@ -135,10 +135,12 @@ class ResetEvent<F> {
 import {ObservableArray} from "./ObservableArray";
 import {ListObserver} from "../../mocks/ListObserver.js";
 
+
+// eslint-disable-next-line @typescript-eslint/explicit-function-return-type
 export function tests() {
     return {
-        "events are emitted in order": async assert => {
+        "events are emitted in order": async (assert): Promise<void> => {
-            const double = n => n * n;
+            const double = (n: number): number => n * n;
             const source = new ObservableArray<number>();
             const mapper = new AsyncMappedList(source, async n => {
                 await new Promise(r => setTimeout(r, n));
@@ -150,7 +152,7 @@ export function tests() {
             mapper.subscribe(observer);
             source.append(2); // will sleep this amount, so second append would take less time
             source.append(1);
-            source.update(0, 7, "lucky seven")
+            source.update(0, 7, "lucky seven");
             source.remove(0);
             {
                 const {type, index, value} = await observer.next();
@@ -182,5 +184,5 @@ export function tests() {
                 assert.equal(value.n, 49);
             }
         }
-    }
+    };
 }

src/observable/list/BaseMappedList.ts

@@ -37,15 +37,15 @@ export class BaseMappedList<F,T,R = T> extends BaseObservableList<T> {
         this._removeCallback = removeCallback;
     }
 
-    findAndUpdate(predicate: (value: T) => boolean, updater: (value: T) => any | false) {
+    findAndUpdate(predicate: (value: T) => boolean, updater: (value: T) => any | false): boolean {
         return findAndUpdateInArray(predicate, this._mappedValues!, this, updater);
     }
 
-    get length() {
+    get length(): number {
         return this._mappedValues!.length;
     }
 
-    [Symbol.iterator]() {
+    [Symbol.iterator](): IterableIterator<T> {
         return this._mappedValues!.values();
     }
 }

src/observable/list/BaseObservableList.ts

@@ -26,17 +26,17 @@ export interface IListObserver<T> {
 
 export function defaultObserverWith<T>(overrides: { [key in keyof IListObserver<T>]?: IListObserver<T>[key] }): IListObserver<T> {
     const defaults = {
-        onReset(){},
+        onReset(): void {},
-        onAdd(){},
+        onAdd(): void {},
-        onUpdate(){},
+        onUpdate(): void {},
-        onRemove(){},
+        onRemove(): void {},
-        onMove(){},
+        onMove(): void {},
-    }
+    };
     return Object.assign(defaults, overrides);
 }
 
 export abstract class BaseObservableList<T> extends BaseObservable<IListObserver<T>> implements Iterable<T> {
-    emitReset() {
+    emitReset(): void {
         for(let h of this._handlers) {
             h.onReset(this);
         }

src/observable/list/ConcatList.ts

@@ -47,7 +47,7 @@ export class ConcatList<T> extends BaseObservableList<T> implements IListObserve
     onReset(): void {
         // TODO: not ideal if other source lists are large
         // but working impl for now
-        // reset, and 
+        // reset, and
         this.emitReset();
         let idx = 0;
         for(const item of this) {
@@ -86,11 +86,11 @@ export class ConcatList<T> extends BaseObservableList<T> implements IListObserve
         return len;
     }
 
-    [Symbol.iterator]() {
+    [Symbol.iterator](): Iterator<T> {
         let sourceListIdx = 0;
         let it = this._sourceLists[0][Symbol.iterator]();
         return {
-            next: () => {
+            next: (): IteratorResult<T> => {
                 let result = it.next();
                 while (result.done) {
                     sourceListIdx += 1;
@@ -102,22 +102,25 @@ export class ConcatList<T> extends BaseObservableList<T> implements IListObserve
                 }
                 return result;
             }
-        }
+        };
     }
 }
 
 import {ObservableArray} from "./ObservableArray";
 import {defaultObserverWith} from "./BaseObservableList";
+
+
+// eslint-disable-next-line @typescript-eslint/explicit-function-return-type
 export async function tests() {
     return {
-        test_length(assert) {
+        test_length(assert): void {
             const all = new ConcatList(
                 new ObservableArray([1, 2, 3]),
                 new ObservableArray([11, 12, 13])
             );
             assert.equal(all.length, 6);
         },
-        test_iterator(assert) {
+        test_iterator(assert): void {
             const all = new ConcatList(
                 new ObservableArray([1, 2, 3]),
                 new ObservableArray([11, 12, 13])
@@ -131,7 +134,7 @@ export async function tests() {
             assert.equal(it.next().value, 13);
             assert(it.next().done);
         },
-        test_add(assert) {
+        test_add(assert): void {
             const list1 = new ObservableArray([1, 2, 3]);
             const list2 = new ObservableArray([11, 12, 13]);
             const all = new ConcatList(list1, list2);
@@ -146,7 +149,7 @@ export async function tests() {
             list2.insert(1, 11.5);
             assert(fired);
         },
-        test_update(assert) {
+        test_update(assert): void {
             const list1 = new ObservableArray([1, 2, 3]);
             const list2 = new ObservableArray([11, 12, 13]);
             const all = new ConcatList(list1, list2);

src/observable/list/MappedList.ts

@@ -19,7 +19,7 @@ import {IListObserver} from "./BaseObservableList";
 import {BaseMappedList, runAdd, runUpdate, runRemove, runMove, runReset} from "./BaseMappedList";
 
 export class MappedList<F,T> extends BaseMappedList<F,T> implements IListObserver<F> {
-    onSubscribeFirst() {
+    onSubscribeFirst(): void {
         this._sourceUnsubscribe = this._sourceList.subscribe(this);
         this._mappedValues = [];
         for (const item of this._sourceList) {
@@ -61,18 +61,21 @@ import {ObservableArray} from "./ObservableArray";
 import {BaseObservableList} from "./BaseObservableList";
 import {defaultObserverWith} from "./BaseObservableList";
 
+// eslint-disable-next-line @typescript-eslint/explicit-function-return-type
 export async function tests() {
     class MockList extends BaseObservableList<number> {
-        get length() {
+        get length(): 0 {
             return 0;
         }
+
+        // eslint-disable-next-line @typescript-eslint/explicit-function-return-type
         [Symbol.iterator]() {
             return [].values();
         }
     }
 
     return {
-        test_add(assert) {
+        test_add(assert): void {
             const source = new MockList();
             const mapped = new MappedList(source, n => {return {n: n*n};});
             let fired = false;
@@ -87,7 +90,7 @@ export async function tests() {
             assert(fired);
             unsubscribe();
         },
-        test_update(assert) {
+        test_update(assert): void {
             const source = new MockList();
             const mapped = new MappedList<number, { n: number, m?: number }>(
                 source,
@@ -109,7 +112,7 @@ export async function tests() {
             assert(fired);
             unsubscribe();
         },
-        "test findAndUpdate not found": assert => {
+        "test findAndUpdate not found": (assert): void => {
             const source = new ObservableArray([1, 3, 4]);
             const mapped = new MappedList(
                 source,
@@ -123,7 +126,7 @@ export async function tests() {
                 () => assert.fail()
             ), false);
         },
-        "test findAndUpdate found but updater bails out of update": assert => {
+        "test findAndUpdate found but updater bails out of update": (assert): void => {
             const source = new ObservableArray([1, 3, 4]);
             const mapped = new MappedList(
                 source,
@@ -143,7 +146,7 @@ export async function tests() {
             ), true);
             assert.equal(fired, true);
         },
-        "test findAndUpdate emits update": assert => {
+        "test findAndUpdate emits update": (assert): void => {
             const source = new ObservableArray([1, 3, 4]);
             const mapped = new MappedList(
                 source,
@@ -161,6 +164,6 @@ export async function tests() {
             assert.equal(mapped.findAndUpdate(n => n === 9, () => "param"), true);
             assert.equal(fired, true);
         },
-        
+
     };
 }

src/observable/list/ObservableArray.ts

@@ -75,7 +75,7 @@ export class ObservableArray<T> extends BaseObservableList<T> {
         return this._items.length;
     }
 
-    [Symbol.iterator]() {
+    [Symbol.iterator](): IterableIterator<T> {
         return this._items.values();
     }
 }

src/observable/list/SortedArray.ts

@@ -87,7 +87,7 @@ export class SortedArray<T> extends BaseObservableList<T> {
         const idx = sortedIndex(this._items, item, this._comparator);
         if (idx >= this._items.length || this._comparator(this._items[idx], item) !== 0) {
             this._items.splice(idx, 0, item);
-            this.emitAdd(idx, item)
+            this.emitAdd(idx, item);
         } else {
             this._items[idx] = item;
             this.emitUpdate(idx, item, updateParams);
@@ -112,52 +112,46 @@ export class SortedArray<T> extends BaseObservableList<T> {
         return this._items.length;
     }
 
-    [Symbol.iterator]() {
+    [Symbol.iterator](): Iterator<T> {
         return new Iterator(this);
     }
 }
 
 // iterator that works even if the current value is removed while iterating
 class Iterator<T> {
-    private _sortedArray: SortedArray<T> | null
+    private _sortedArray: SortedArray<T>;
-    private _current: T | null | undefined
+    private _current: T | null | undefined;
+    private _consumed: boolean = false;
 
     constructor(sortedArray: SortedArray<T>) {
         this._sortedArray = sortedArray;
         this._current = null;
     }
 
-    next() {
+    next(): IteratorResult<T> {
-        if (this._sortedArray) {
+        if (this._consumed) {
-            if (this._current) {
+            return {value: undefined, done: true};
-                this._current = this._sortedArray._getNext(this._current);
-            } else {
-                this._current = this._sortedArray.get(0);
-            }
-            if (this._current) {
-                return {value: this._current};
-            } else {
-                // cause done below
-                this._sortedArray = null;
-            }
         }
-        if (!this._sortedArray) {
+        this._current = this._current? this._sortedArray._getNext(this._current): this._sortedArray.get(0);
-            return {done: true};
+        if (!this._current) {
+            this._consumed = true;
         }
+        return { value: this._current, done: this._consumed } as IteratorResult<T>;
     }
 }
 
+// eslint-disable-next-line @typescript-eslint/explicit-function-return-type
 export function tests() {
     return {
-        "setManyUnsorted": assert => {
+        "setManyUnsorted": (assert): void => {
             const sa = new SortedArray<string>((a, b) => a.localeCompare(b));
             sa.setManyUnsorted(["b", "a", "c"]);
             assert.equal(sa.length, 3);
             assert.equal(sa.get(0), "a");
             assert.equal(sa.get(1), "b");
             assert.equal(sa.get(2), "c");
-        }, 
+        },
-        "_getNext": assert => {
+        "_getNext": (assert): void => {
             const sa = new SortedArray<string>((a, b) => a.localeCompare(b));
             sa.setManyUnsorted(["b", "a", "f"]);
             assert.equal(sa._getNext("a"), "b");
@@ -166,7 +160,7 @@ export function tests() {
             assert.equal(sa._getNext("c"), "f");
             assert.equal(sa._getNext("f"), undefined);
         },
-        "iterator with removals": assert => {
+        "iterator with removals": (assert): void => {
             const queue = new SortedArray<{idx: number}>((a, b) => a.idx - b.idx);
             queue.setManyUnsorted([{idx: 5}, {idx: 3}, {idx: 1}, {idx: 4}, {idx: 2}]);
             const it = queue[Symbol.iterator]();
@@ -183,5 +177,5 @@ export function tests() {
             // check done persists
             assert.equal(it.next().done, true);
         }
-    }
+    };
 }

src/observable/list/SortedMapList.js

@@ -53,7 +53,7 @@ export class SortedMapList extends BaseObservableList {
         this._sortedPairs = null;
         this._mapSubscription = null;
     }
-    
+
     onAdd(key, value) {
         const pair = {key, value};
         const idx = sortedIndex(this._sortedPairs, pair, this._comparator);
@@ -129,11 +129,11 @@ export class SortedMapList extends BaseObservableList {
                 }
                 return v;
             }
-        }
+        };
     }
 }
 
-import {ObservableMap} from "../map/ObservableMap";
+import {ObservableMap} from "../";
 
 export function tests() {
     return {
@@ -267,5 +267,5 @@ export function tests() {
             assert.equal(updateFired, 1);
             assert.deepEqual(Array.from(list).map(v => v.number), [1, 3, 11]);
         },
-    }
+    };
 }

src/observable/list/common.ts

@@ -17,7 +17,12 @@ limitations under the License.
 import {BaseObservableList} from "./BaseObservableList";
 
 /* inline update of item in collection backed by array, without replacing the preexising item */
-export function findAndUpdateInArray<T>(predicate: (value: T) => boolean, array: T[], observable: BaseObservableList<T>, updater: (value: T) => any | false) {
+export function findAndUpdateInArray<T>(
+    predicate: (value: T) => boolean,
+    array: T[],
+    observable: BaseObservableList<T>,
+    updater: (value: T) => any | false
+): boolean {
     const index = array.findIndex(predicate);
     if (index !== -1) {
         const value = array[index];

src/observable/map/ApplyMap.ts

@@ -14,52 +14,62 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {BaseObservableMap} from "./BaseObservableMap";
+import {BaseObservableMap} from "./index";
+import {SubscriptionHandle} from "../BaseObservable";
 
-export class ApplyMap extends BaseObservableMap {
+
-    constructor(source, apply) {
+/*
+This class MUST never be imported directly from here.
+Instead, it MUST be imported from index.ts. See the
+top level comment in index.ts for details.
+*/
+export class ApplyMap<K, V> extends BaseObservableMap<K, V> {
+    private _source: BaseObservableMap<K, V>;
+    private _subscription?: SubscriptionHandle;
+    private _apply?: Apply<K, V>;
+
+    constructor(source: BaseObservableMap<K, V>, apply?: Apply<K, V>) {
         super();
         this._source = source;
         this._apply = apply;
-        this._subscription = null;
     }
 
-    hasApply() {
+    hasApply(): boolean {
         return !!this._apply;
     }
 
-    setApply(apply) {
+    setApply(apply?: Apply<K, V>): void {
         this._apply = apply;
-        if (apply) {
+        if (this._apply) {
             this.applyOnce(this._apply);
         }
     }
 
-    applyOnce(apply) {
+    applyOnce(apply: Apply<K, V>): void {
         for (const [key, value] of this._source) {
             apply(key, value);
         }
     }
 
-    onAdd(key, value) {
+    onAdd(key: K, value: V): void {
         if (this._apply) {
             this._apply(key, value);
         }
         this.emitAdd(key, value);
     }
 
-    onRemove(key, value) {
+    onRemove(key: K, value: V): void {
         this.emitRemove(key, value);
     }
 
-    onUpdate(key, value, params) {
+    onUpdate(key: K, value: V, params: any): void {
         if (this._apply) {
             this._apply(key, value, params);
         }
         this.emitUpdate(key, value, params);
     }
 
-    onSubscribeFirst() {
+    onSubscribeFirst(): void {
         this._subscription = this._source.subscribe(this);
         if (this._apply) {
             this.applyOnce(this._apply);
@@ -67,27 +77,31 @@ export class ApplyMap extends BaseObservableMap {
         super.onSubscribeFirst();
     }
 
-    onUnsubscribeLast() {
+    onUnsubscribeLast(): void {
         super.onUnsubscribeLast();
-        this._subscription = this._subscription();
+        if (this._subscription) {
+            this._subscription = this._subscription();
+        }
     }
 
-    onReset() {
+    onReset(): void {
         if (this._apply) {
             this.applyOnce(this._apply);
         }
         this.emitReset();
     }
 
-    [Symbol.iterator]() {
+    [Symbol.iterator](): Iterator<[K, V]> {
         return this._source[Symbol.iterator]();
     }
 
-    get size() {
+    get size(): number {
         return this._source.size;
     }
 
-    get(key) {
+    get(key: K): V | undefined {
         return this._source.get(key);
     }
 }
+
+type Apply<K, V> = (key: K, value: V, params?: any) => void;

src/observable/map/BaseObservableMap.ts

@@ -15,6 +15,11 @@ limitations under the License.
 */
 
 import {BaseObservable} from "../BaseObservable";
+import {JoinedMap} from "./index";
+import {MappedMap} from "./index";
+import {FilteredMap} from "./index";
+import {SortedMapList} from "../list/SortedMapList.js";
+
 
 export interface IMapObserver<K, V> {
     onReset(): void;
@@ -23,33 +28,70 @@ export interface IMapObserver<K, V> {
     onRemove(key: K, value: V): void
 }
 
+/*
+This class MUST never be imported directly from here.
+Instead, it MUST be imported from index.ts. See the
+top level comment in index.ts for details.
+*/
 export abstract class BaseObservableMap<K, V> extends BaseObservable<IMapObserver<K, V>> {
-    emitReset() {
+
+    constructor() {
+        super();
+    }
+
+    emitReset(): void {
         for(let h of this._handlers) {
             h.onReset();
         }
     }
     // we need batch events, mostly on index based collection though?
     // maybe we should get started without?
-    emitAdd(key: K, value: V) {
+    emitAdd(key: K, value: V): void {
         for(let h of this._handlers) {
             h.onAdd(key, value);
         }
     }
 
-    emitUpdate(key, value, params) {
+    emitUpdate(key: K, value: V, params: any): void {
         for(let h of this._handlers) {
             h.onUpdate(key, value, params);
         }
     }
 
-    emitRemove(key, value) {
+    emitRemove(key: K, value: V): void {
         for(let h of this._handlers) {
             h.onRemove(key, value);
         }
     }
 
+    join(...otherMaps: Array<typeof this>): JoinedMap<K, V> {
+        return new JoinedMap([this].concat(otherMaps));
+     }
+
+     mapValues<MappedV>(mapper: Mapper<V, MappedV>, updater?: Updater<V, MappedV>): MappedMap<K, V, MappedV> {
+         return new MappedMap(this, mapper, updater);
+     }
+
+     sortValues(comparator: Comparator<V>): SortedMapList {
+         return new SortedMapList(this, comparator);
+     }
+
+     filterValues(filter: Filter<K, V>): FilteredMap<K, V> {
+         return new FilteredMap(this, filter);
+     }
+
     abstract [Symbol.iterator](): Iterator<[K, V]>;
     abstract get size(): number;
     abstract get(key: K): V | undefined;
 }
+
+export type Mapper<V, MappedV> = (
+    value: V,
+    emitSpontaneousUpdate: any,
+) => MappedV;
+
+export type Updater<V, MappedV> = (params: any, mappedValue?: MappedV, value?: V) => void;
+
+export type Comparator<V> = (a: V, b: V) => number;
+
+export type Filter<K, V> = (v: V, k: K) => boolean;

src/observable/map/FilteredMap.ts

@@ -14,19 +14,28 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {BaseObservableMap} from "./BaseObservableMap";
+import {BaseObservableMap, Filter} from "./index";
+import {SubscriptionHandle} from "../BaseObservable";
 
-export class FilteredMap extends BaseObservableMap {
+
-    constructor(source, filter) {
+/*
+This class MUST never be imported directly from here.
+Instead, it MUST be imported from index.ts. See the
+top level comment in index.ts for details.
+*/
+export class FilteredMap<K, V> extends BaseObservableMap<K, V> {
+    private _source: BaseObservableMap<K, V>;
+    private _filter: Filter<K, V>;
+    private _included?: Map<K, boolean>;
+    private _subscription?: SubscriptionHandle;
+
+    constructor(source: BaseObservableMap<K, V>, filter: Filter<K, V>) {
         super();
         this._source = source;
         this._filter = filter;
-        /** @type {Map<string, bool>} */
-        this._included = null;
-        this._subscription = null;
     }
 
-    setFilter(filter) {
+    setFilter(filter: Filter<K, V>): void {
         this._filter = filter;
         if (this._subscription) {
             this._reapplyFilter();
@@ -36,7 +45,7 @@ export class FilteredMap extends BaseObservableMap {
     /**
      * reapply the filter
      */
-    _reapplyFilter(silent = false) {
+    _reapplyFilter(silent = false): void {
         if (this._filter) {
             const oldIncluded = this._included;
             this._included = this._included || new Map();
@@ -58,30 +67,38 @@ export class FilteredMap extends BaseObservableMap {
                     }
                 }
             }
-            this._included = null;
+            this._included = undefined;
         }
     }
 
-    onAdd(key, value) {
+    onAdd(key: K, value: V): void {
         if (this._filter) {
-            const included = this._filter(value, key);
+            if (this._included) {
-            this._included.set(key, included);
+                const included = this._filter(value, key);
-            if (!included) {
+                this._included.set(key, included);
-                return;
+                if (!included) {
+                    return;
+                }
+            } else {
+                throw new Error("Internal logic error: FilteredMap._included used before initialized");
             }
         }
         this.emitAdd(key, value);
     }
 
-    onRemove(key, value) {
+    onRemove(key: K, value: V): void {
-        const wasIncluded = !this._filter || this._included.get(key);
+        const wasIncluded = !this._filter || this._included?.get(key);
-        this._included.delete(key);
+        if (this._included) {
-        if (wasIncluded) {
+            this._included.delete(key);
-            this.emitRemove(key, value);
+            if (wasIncluded) {
+                this.emitRemove(key, value);
+            }
+        } else {
+            throw new Error("Internal logic error: FilteredMap._included used before initialized");
         }
     }
 
-    onUpdate(key, value, params) {
+    onUpdate(key: K, value: V, params: any): void {
         // if an update is emitted while calling source.subscribe() from onSubscribeFirst, ignore it
         if (!this._included) {
             return;
@@ -96,7 +113,7 @@ export class FilteredMap extends BaseObservableMap {
         }
     }
 
-    _emitForUpdate(wasIncluded, isIncluded, key, value, params = null) {
+    _emitForUpdate(wasIncluded: boolean | undefined, isIncluded: boolean, key: K, value: V, params: any = null): void {
         if (wasIncluded && !isIncluded) {
             this.emitRemove(key, value);
         } else if (!wasIncluded && isIncluded) {
@@ -106,30 +123,32 @@ export class FilteredMap extends BaseObservableMap {
         }
     }
 
-    onSubscribeFirst() {
+    onSubscribeFirst(): void {
         this._subscription = this._source.subscribe(this);
         this._reapplyFilter(true);
         super.onSubscribeFirst();
     }
 
-    onUnsubscribeLast() {
+    onUnsubscribeLast(): void {
         super.onUnsubscribeLast();
-        this._included = null;
+        this._included = undefined;
-        this._subscription = this._subscription();
+        if (this._subscription) {
+            this._subscription = this._subscription();
+        }
     }
 
-    onReset() {
+    onReset(): void {
         this._reapplyFilter();
         this.emitReset();
     }
 
-    [Symbol.iterator]() {
+    [Symbol.iterator](): FilterIterator<K, V> {
-        return new FilterIterator(this._source, this._included);
+        return new FilterIterator<K, V>(this._source, this._included);
     }
 
-    get size() {
+    get size(): number {
         let count = 0;
-        this._included.forEach(included => {
+        this._included?.forEach(included => {
             if (included) {
                 count += 1;
             }
@@ -137,7 +156,7 @@ export class FilteredMap extends BaseObservableMap {
         return count;
     }
 
-    get(key) {
+    get(key: K): V | undefined {
         const value = this._source.get(key);
         if (value && this._filter(value, key)) {
             return value;
@@ -145,13 +164,15 @@ export class FilteredMap extends BaseObservableMap {
     }
 }
 
-class FilterIterator {
+class FilterIterator<K, V> {
-    constructor(map, _included) {
+    private _included?: Map<K, boolean>
-        this._included = _included;
+    private _sourceIterator: Iterator<[K, V], any, undefined>
+    constructor(map: BaseObservableMap<K, V>, included?: Map<K, boolean>) {
+        this._included = included;
         this._sourceIterator = map[Symbol.iterator]();
     }
 
-    next() {
+    next(): IteratorResult<[K, V]> {
         // eslint-disable-next-line no-constant-condition
         while (true) {
             const sourceResult = this._sourceIterator.next();
@@ -159,47 +180,62 @@ class FilterIterator {
                 return sourceResult;
             }
             const key = sourceResult.value[0];
-            if (this._included.get(key)) {
+            if (this._included?.get(key)) {
                 return sourceResult;
             }
         }
     }
 }
 
-import {ObservableMap} from "./ObservableMap";
+import {ObservableMap} from "..";
+
+// eslint-disable-next-line @typescript-eslint/explicit-function-return-type
 export function tests() {
     return {
-        "filter preloaded list": assert => {
+        "filter preloaded list": (assert): void => {
             const source = new ObservableMap();
             source.add("one", 1);
             source.add("two", 2);
             source.add("three", 3);
-            const oddNumbers = new FilteredMap(source, x => x % 2 !== 0);
+            const oddNumbers = new FilteredMap(source, (x: number) => x % 2 !== 0);
             // can only iterate after subscribing
-            oddNumbers.subscribe({});
+            oddNumbers.subscribe({
+                onAdd() {
+                    return;
+                },
+                onRemove() {
+                    return;
+                },
+                onUpdate() {
+                    return;
+                },
+                onReset() {
+                    return;
+                },
+            });
             assert.equal(oddNumbers.size, 2);
             const it = oddNumbers[Symbol.iterator]();
             assert.deepEqual(it.next().value, ["one", 1]);
             assert.deepEqual(it.next().value, ["three", 3]);
             assert.equal(it.next().done, true);
         },
-        // "filter added values": assert => {
+        // "filter added values": (assert): void => {
 
         // },
-        // "filter removed values": assert => {
+        // "filter removed values": (assert): void => {
 
         // },
-        // "filter changed values": assert => {
+        // "filter changed values": (assert): void => {
 
         // },
 
-        "emits must trigger once": assert => {
+        "emits must trigger once": (assert): void => {
             const source = new ObservableMap();
             let count_add = 0, count_update = 0, count_remove = 0;
             source.add("num1", 1);
             source.add("num2", 2);
             source.add("num3", 3);
-            const oddMap = new FilteredMap(source, x => x % 2 !== 0);
+            const oddMap = new FilteredMap(source, (x: number) => x % 2 !== 0);
             oddMap.subscribe({
                 onAdd() {
                     count_add += 1;
@@ -209,6 +245,9 @@ export function tests() {
                 },
                 onUpdate() {
                     count_update += 1;
+                },
+                onReset() {
+                    return;
                 }
             });
             source.set("num3", 4);
@@ -218,5 +257,5 @@ export function tests() {
             assert.strictEqual(count_update, 1);
             assert.strictEqual(count_remove, 1);
         }
-    }
+    };
 }

src/observable/map/JoinedMap.ts

@@ -14,16 +14,25 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {BaseObservableMap} from "./BaseObservableMap";
+import {BaseObservableMap} from ".";
+import {SubscriptionHandle} from "../BaseObservable";
 
-export class JoinedMap extends BaseObservableMap {
+
-    constructor(sources) {
+/*
+This class MUST never be imported directly from here.
+Instead, it MUST be imported from index.ts. See the
+top level comment in index.ts for details.
+*/
+export class JoinedMap<K, V> extends BaseObservableMap<K, V> {
+    protected _sources: BaseObservableMap<K, V>[];
+    private _subscriptions?: SourceSubscriptionHandler<K, V>[];
+
+    constructor(sources: BaseObservableMap<K, V>[]) {
         super();
         this._sources = sources;
-        this._subscriptions = null;
     }
 
-    onAdd(source, key, value) {
+    onAdd(source: BaseObservableMap<K, V>, key: K, value: V): void {
         if (!this._isKeyAtSourceOccluded(source, key)) {
             const occludingValue = this._getValueFromOccludedSources(source, key);
             if (occludingValue !== undefined) {
@@ -35,7 +44,7 @@ export class JoinedMap extends BaseObservableMap {
         }
     }
 
-    onRemove(source, key, value) {
+    onRemove(source: BaseObservableMap<K, V>, key: K, value: V): void {
         if (!this._isKeyAtSourceOccluded(source, key)) {
             this.emitRemove(key, value);
             const occludedValue = this._getValueFromOccludedSources(source, key);
@@ -47,7 +56,7 @@ export class JoinedMap extends BaseObservableMap {
         }
     }
 
-    onUpdate(source, key, value, params) {
+    onUpdate(source: BaseObservableMap<K, V>, key: K, value: V, params: any): void {
         // if an update is emitted while calling source.subscribe() from onSubscribeFirst, ignore it
         if (!this._subscriptions) {
             return;
@@ -57,16 +66,16 @@ export class JoinedMap extends BaseObservableMap {
         }
     }
 
-    onReset() {
+    onReset(): void {
         this.emitReset();
     }
 
-    onSubscribeFirst() {
+    onSubscribeFirst(): void {
         this._subscriptions = this._sources.map(source => new SourceSubscriptionHandler(source, this).subscribe());
         super.onSubscribeFirst();
     }
 
-    _isKeyAtSourceOccluded(source, key) {
+    _isKeyAtSourceOccluded(source: BaseObservableMap<K, V>, key: K): boolean {
         // sources that come first in the sources array can
         // hide the keys in later sources, to prevent events
         // being emitted for the same key and different values,
@@ -81,7 +90,7 @@ export class JoinedMap extends BaseObservableMap {
     }
 
     // get the value that the given source and key occlude, if any
-    _getValueFromOccludedSources(source, key) {
+    _getValueFromOccludedSources(source: BaseObservableMap<K, V>, key: K): V | undefined{
         // sources that come first in the sources array can
         // hide the keys in later sources, to prevent events
         // being emitted for the same key and different values,
@@ -97,53 +106,58 @@ export class JoinedMap extends BaseObservableMap {
         return undefined;
     }
 
-    onUnsubscribeLast() {
+    onUnsubscribeLast(): void {
         super.onUnsubscribeLast();
-        for (const s of this._subscriptions) {
+        if (this._subscriptions) {
-            s.dispose();
+            for (const s of this._subscriptions) {
+                s.dispose();
+            }
         }
     }
 
+    // eslint-disable-next-line @typescript-eslint/explicit-function-return-type
     [Symbol.iterator]() {
-        return new JoinedIterator(this._sources);
+        return new JoinedIterator<K, V>(this._sources);
     }
 
-    get size() {
+    get size(): number {
         return this._sources.reduce((sum, s) => sum + s.size, 0);
     }
 
-    get(key) {
+    get(key: K): V | undefined {
         for (const s of this._sources) {
             const value = s.get(key);
             if (value) {
                 return value;
             }
         }
-        return null;
+        return undefined;
     }
 }
 
-class JoinedIterator {
+class JoinedIterator<K, V> implements Iterator<[K, V]> {
-    constructor(sources) {
+    private _sources: {[Symbol.iterator](): Iterator<[K, V]>}[];
+    private _sourceIndex = -1;
+    private _encounteredKeys = new Set();
+    private _currentIterator?: Iterator<[K, V]>
+
+    constructor(sources: {[Symbol.iterator](): Iterator<[K, V]>}[]) {
         this._sources = sources;
-        this._sourceIndex = -1;
-        this._currentIterator = null;
-        this._encounteredKeys = new Set();
     }
 
-    next() {
+    next(): IteratorYieldResult<[K, V]> | IteratorReturnResult<null> {
-        let result;
+        let result: IteratorYieldResult<[K, V]> | undefined = undefined;
         while (!result) {
             if (!this._currentIterator) {
                 this._sourceIndex += 1;
                 if (this._sources.length <= this._sourceIndex) {
-                    return {done: true};
+                    return {done: true, value: null};
                 }
                 this._currentIterator = this._sources[this._sourceIndex][Symbol.iterator]();
             }
-            const sourceResult = this._currentIterator.next();
+            const sourceResult = this._currentIterator?.next();
-            if (sourceResult.done) {
+            if (!sourceResult || sourceResult.done) {
-                this._currentIterator = null;
+                this._currentIterator = undefined;
                 continue;
             } else {
                 const key = sourceResult.value[0];
@@ -157,66 +171,73 @@ class JoinedIterator {
     }
 }
 
-class SourceSubscriptionHandler {
+class SourceSubscriptionHandler<K, V> {
-    constructor(source, joinedMap) {
+    private _source: BaseObservableMap<K, V>;
+    private _joinedMap: JoinedMap<K, V>;
+    private _subscription?: SubscriptionHandle;
+
+    constructor(source: BaseObservableMap<K, V>, joinedMap: JoinedMap<K, V>) {
         this._source = source;
         this._joinedMap = joinedMap;
-        this._subscription = null;
+        this._subscription = undefined;
     }
 
-    subscribe() {
+    subscribe(): this {
         this._subscription = this._source.subscribe(this);
         return this;
     }
 
-    dispose() {
+    dispose(): void {
-        this._subscription = this._subscription();
+        if (this._subscription) this._subscription = this._subscription();
     }
 
-    onAdd(key, value) {
+    onAdd(key: K, value: V): void {
         this._joinedMap.onAdd(this._source, key, value);
     }
 
-    onRemove(key, value) {
+    onRemove(key: K, value: V): void {
         this._joinedMap.onRemove(this._source, key, value);
     }
 
-    onUpdate(key, value, params) {
+    onUpdate(key: K, value: V, params: any): void {
         this._joinedMap.onUpdate(this._source, key, value, params);
     }
 
-    onReset() {
+    onReset(): void {
-        this._joinedMap.onReset(this._source);
+        this._joinedMap.onReset();
     }
 }
 
 
-import { ObservableMap } from "./ObservableMap";
+import {ObservableMap} from "..";
 
+// eslint-disable-next-line @typescript-eslint/explicit-function-return-type
 export function tests() {
-
+    function observeMap(map: JoinedMap<any, any>): { type: string; key: any; value: any; params?: any; }[] {
-    function observeMap(map) {
+        const events: { type: string, key: any, value: any, params?: any }[] = [];
-        const events = [];
         map.subscribe({
-            onAdd(key, value) { events.push({type: "add", key, value}); },
+            onAdd(key, value) { events.push({ type: "add", key, value }); },
-            onRemove(key, value) { events.push({type: "remove", key, value}); },
+            onRemove(key, value) { events.push({ type: "remove", key, value }); },
-            onUpdate(key, value, params) { events.push({type: "update", key, value, params}); }
+            onUpdate(key, value, params) { events.push({ type: "update", key, value, params }); },
+            onReset: function (): void {
+                return;
+            }
         });
         return events;
     }
 
     return {
-        "joined iterator": assert => {
+        "joined iterator": (assert): void => {
-            const firstKV = ["a", 1];
+            const firstKV: [string, number] = ["a", 1];
-            const secondKV = ["b", 2];
+            const secondKV: [string, number] = ["b", 2];
-            const thirdKV = ["c", 3];
+            const thirdKV: [string, number] = ["c", 3];
-            const it = new JoinedIterator([[firstKV, secondKV], [thirdKV]]);
+            const it = new JoinedIterator<string, number>([[firstKV, secondKV], [thirdKV]]);
             assert.equal(it.next().value, firstKV);
             assert.equal(it.next().value, secondKV);
             assert.equal(it.next().value, thirdKV);
             assert.equal(it.next().done, true);
         },
-        "prevent key collision during iteration": assert => {
+        "prevent key collision during iteration": (assert): void => {
             const first = new ObservableMap();
             const second = new ObservableMap();
             const join = new JoinedMap([first, second]);
@@ -228,7 +249,7 @@ export function tests() {
             assert.deepEqual(it.next().value, ["b", 3]);
             assert.equal(it.next().done, true);
         },
-        "adding occluded key doesn't emit add": assert => {
+        "adding occluded key doesn't emit add": (assert): void => {
             const first = new ObservableMap();
             const second = new ObservableMap();
             const join = new JoinedMap([first, second]);
@@ -240,7 +261,7 @@ export function tests() {
             assert.equal(events[0].key, "a");
             assert.equal(events[0].value, 1);
         },
-        "updating occluded key doesn't emit update": assert => {
+        "updating occluded key doesn't emit update": (assert): void => {
             const first = new ObservableMap();
             const second = new ObservableMap();
             const join = new JoinedMap([first, second]);
@@ -250,7 +271,7 @@ export function tests() {
             second.update("a", 3);
             assert.equal(events.length, 0);
         },
-        "removal of occluding key emits add after remove": assert => {
+        "removal of occluding key emits add after remove": (assert): void => {
             const first = new ObservableMap();
             const second = new ObservableMap();
             const join = new JoinedMap([first, second]);
@@ -266,7 +287,7 @@ export function tests() {
             assert.equal(events[1].key, "a");
             assert.equal(events[1].value, 2);
         },
-        "adding occluding key emits remove first": assert => {
+        "adding occluding key emits remove first": (assert): void => {
             const first = new ObservableMap();
             const second = new ObservableMap();
             const join = new JoinedMap([first, second]);

src/observable/map/LogMap.js

@@ -1,70 +0,0 @@
-/*
-Copyright 2020 Bruno Windels <bruno@windels.cloud>
-
-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 {BaseObservableMap} from "./BaseObservableMap";
-
-export class LogMap extends BaseObservableMap {
-    constructor(source, log) {
-        super();
-        this._source = source;
-        this.log = log;
-        this._subscription = null;
-    }
-
-    onAdd(key, value) {
-        this.log("add", key, value);
-        this.emitAdd(key, value);
-    }
-
-    onRemove(key, value) {
-        this.log("remove", key, value);
-        this.emitRemove(key, value);
-    }
-
-    onUpdate(key, value, params) {
-        this.log("update", key, value, params);
-        this.emitUpdate(key, value, params);
-    }
-
-    onSubscribeFirst() {
-        this.log("subscribeFirst");
-        this._subscription = this._source.subscribe(this);
-        super.onSubscribeFirst();
-    }
-
-    onUnsubscribeLast() {
-        super.onUnsubscribeLast();
-        this._subscription = this._subscription();
-        this.log("unsubscribeLast");
-    }
-
-    onReset() {
-        this.log("reset");
-        this.emitReset();
-    }
-
-    [Symbol.iterator]() {
-        return this._source[Symbol.iterator]();
-    }
-
-    get size() {
-        return this._source.size;
-    }
-
-    get(key) {
-        return this._source.get(key);
-    }
-}

src/observable/map/LogMap.ts

@@ -0,0 +1,86 @@
+/*
+Copyright 2020 Bruno Windels <bruno@windels.cloud>
+
+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 {BaseObservableMap} from "./index";
+import {SubscriptionHandle} from "../BaseObservable";
+import {ILogItem, LabelOrValues} from "../../logging/types";
+import {LogLevel} from "../../logging/LogFilter";
+
+
+/*
+This class MUST never be imported directly from here.
+Instead, it MUST be imported from index.ts. See the
+top level comment in index.ts for details.
+*/
+export class LogMap<K, V> extends BaseObservableMap<K, V> {
+    private _source: BaseObservableMap<K, V>;
+    private _subscription?: SubscriptionHandle;
+    private _log: ILogItem;
+
+    constructor(source: BaseObservableMap<K, V>, log: ILogItem) {
+        super();
+        this._source = source;
+        this._log = log;
+    }
+
+    private log(labelOrValues: LabelOrValues, logLevel?: LogLevel): ILogItem {
+        return this._log.log(labelOrValues, logLevel);
+    }
+
+    onAdd(key: K, value: V): void {
+        this.log("add " + JSON.stringify({key, value}));
+        this.emitAdd(key, value);
+    }
+
+    onRemove(key: K, value: V): void {
+        this.log("remove " + JSON.stringify({key, value}));
+        this.emitRemove(key, value);
+    }
+
+    onUpdate(key: K, value: V, params: any): void {
+        this.log("update" + JSON.stringify({key, value, params}));
+        this.emitUpdate(key, value, params);
+    }
+
+    onSubscribeFirst(): void {
+        this.log("subscribeFirst");
+        this._subscription = this._source.subscribe(this);
+        super.onSubscribeFirst();
+    }
+
+    onUnsubscribeLast(): void {
+        super.onUnsubscribeLast();
+        if (this._subscription) this._subscription = this._subscription();
+        this.log("unsubscribeLast");
+    }
+
+    onReset(): void {
+        this.log("reset");
+        this.emitReset();
+    }
+
+    [Symbol.iterator](): Iterator<[K, V]> {
+        return this._source[Symbol.iterator]();
+    }
+
+    get size(): number {
+        return this._source.size;
+    }
+
+    get(key: K): V | undefined{
+        return this._source.get(key);
+    }
+}

src/observable/map/MappedMap.ts

@@ -14,55 +14,76 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {BaseObservableMap} from "./BaseObservableMap";
+import {BaseObservableMap, Mapper, Updater} from "./index";
+import {SubscriptionHandle} from "../BaseObservable";
+
+
 /*
 so a mapped value can emit updates on it's own with this._emitSpontaneousUpdate that is passed in the mapping function
 how should the mapped value be notified of an update though? and can it then decide to not propagate the update?
 */
-export class MappedMap extends BaseObservableMap {
+/*
-    constructor(source, mapper, updater) {
+This class MUST never be imported directly from here.
+Instead, it MUST be imported from index.ts. See the
+top level comment in index.ts for details.
+*/
+export class MappedMap<K, V, MappedV> extends BaseObservableMap<K, MappedV> {
+    private _source: BaseObservableMap<K, V>;
+    private _mapper: Mapper<V, MappedV>;
+    private _updater?: Updater<V, MappedV>;
+    private _mappedValues: Map<K, MappedV>;
+    private _subscription?: SubscriptionHandle;
+
+
+    constructor(
+        source: BaseObservableMap<K, V>,
+        mapper: Mapper<V, MappedV>,
+        updater?: Updater<V, MappedV>
+    ) {
         super();
         this._source = source;
         this._mapper = mapper;
         this._updater = updater;
-        this._mappedValues = new Map();
+        this._mappedValues = new Map<K, MappedV>();
     }
 
-    _emitSpontaneousUpdate(key, params) {
+    _emitSpontaneousUpdate(key: K, params: any): void {
         const value = this._mappedValues.get(key);
         if (value) {
             this.emitUpdate(key, value, params);
         }
     }
 
-    onAdd(key, value) {
+    onAdd(key: K, value: V): void {
         const emitSpontaneousUpdate = this._emitSpontaneousUpdate.bind(this, key);
         const mappedValue = this._mapper(value, emitSpontaneousUpdate);
         this._mappedValues.set(key, mappedValue);
         this.emitAdd(key, mappedValue);
     }
 
-    onRemove(key/*, _value*/) {
+    onRemove(key: K/*, _value*/): void {
         const mappedValue = this._mappedValues.get(key);
         if (this._mappedValues.delete(key)) {
-            this.emitRemove(key, mappedValue);
+            if (mappedValue) {
+                this.emitRemove(key, mappedValue);
+            }
         }
     }
 
-    onUpdate(key, value, params) {
+    onUpdate(key: K, value: V, params: any): void {
         // if an update is emitted while calling source.subscribe() from onSubscribeFirst, ignore it
         if (!this._mappedValues) {
             return;
         }
         const mappedValue = this._mappedValues.get(key);
         if (mappedValue !== undefined) {
-            this._updater?.(mappedValue, params, value);
+            this._updater?.(params, mappedValue, value);
             // TODO: map params somehow if needed?
             this.emitUpdate(key, mappedValue, params);
         }
     }
 
-    onSubscribeFirst() {
+    onSubscribeFirst(): void {
         this._subscription = this._source.subscribe(this);
         for (let [key, value] of this._source) {
             const emitSpontaneousUpdate = this._emitSpontaneousUpdate.bind(this, key);
@@ -72,26 +93,28 @@ export class MappedMap extends BaseObservableMap {
         super.onSubscribeFirst();
     }
 
-    onUnsubscribeLast() {
+    onUnsubscribeLast(): void {
         super.onUnsubscribeLast();
-        this._subscription = this._subscription();
+        if (this._subscription) {
+            this._subscription = this._subscription();
+        }
         this._mappedValues.clear();
     }
 
-    onReset() {
+    onReset(): void {
         this._mappedValues.clear();
         this.emitReset();
     }
 
-    [Symbol.iterator]() {
+    [Symbol.iterator](): IterableIterator<[K, MappedV]> {
         return this._mappedValues.entries();
     }
 
-    get size() {
+    get size(): number {
         return this._mappedValues.size;
     }
 
-    get(key) {
+    get(key: K): MappedV | undefined {
         return this._mappedValues.get(key);
     }
-}
+}

src/observable/map/ObservableMap.ts

@@ -14,8 +14,14 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {BaseObservableMap} from "./BaseObservableMap";
+import {BaseObservableMap} from "./index";
 
+
+/*
+This class MUST never be imported directly from here.
+Instead, it MUST be imported from index.ts. See the
+top level comment in index.ts for details.
+*/
 export class ObservableMap<K, V> extends BaseObservableMap<K, V> {
     private readonly _values: Map<K, V>;
 
@@ -61,7 +67,7 @@ export class ObservableMap<K, V> extends BaseObservableMap<K, V> {
             // We set the value here because update only supports inline updates
             this._values.set(key, value);
             return this.update(key, undefined);
-        }    
+        }
         else {
             return this.add(key, value);
         }
@@ -93,9 +99,10 @@ export class ObservableMap<K, V> extends BaseObservableMap<K, V> {
     }
 }
 
+// eslint-disable-next-line @typescript-eslint/explicit-function-return-type
 export function tests() {
     return {
-        test_initial_values(assert) {
+        test_initial_values(assert): void {
             const map = new ObservableMap([
                 ["a", 5],
                 ["b", 10]
@@ -105,14 +112,14 @@ export function tests() {
             assert.equal(map.get("b"), 10);
         },
 
-        test_add(assert) {
+        test_add(assert): void {
             let fired = 0;
             const map = new ObservableMap<number, {value: number}>();
             map.subscribe({
                 onAdd(key, value) {
                     fired += 1;
                     assert.equal(key, 1);
-                    assert.deepEqual(value, {value: 5}); 
+                    assert.deepEqual(value, {value: 5});
                 },
                 onUpdate() {},
                 onRemove() {},
@@ -123,7 +130,7 @@ export function tests() {
             assert.equal(fired, 1);
         },
 
-        test_update(assert) {
+        test_update(assert): void {
             let fired = 0;
             const map = new ObservableMap<number, {number: number}>();
             const value = {number: 5};
@@ -132,7 +139,7 @@ export function tests() {
                 onUpdate(key, value, params) {
                     fired += 1;
                     assert.equal(key, 1);
-                    assert.deepEqual(value, {number: 6}); 
+                    assert.deepEqual(value, {number: 6});
                     assert.equal(params, "test");
                 },
                 onAdd() {},
@@ -144,7 +151,7 @@ export function tests() {
             assert.equal(fired, 1);
         },
 
-        test_update_unknown(assert) {
+        test_update_unknown(assert): void {
             let fired = 0;
             const map = new ObservableMap<number, {number: number}>();
             map.subscribe({
@@ -158,19 +165,19 @@ export function tests() {
             assert.equal(result, false);
         },
 
-        test_set(assert) {
+        test_set(assert): void {
             let add_fired = 0, update_fired = 0;
             const map = new ObservableMap<number, {value: number}>();
             map.subscribe({
                 onAdd(key, value) {
                     add_fired += 1;
                     assert.equal(key, 1);
-                    assert.deepEqual(value, {value: 5}); 
+                    assert.deepEqual(value, {value: 5});
                 },
                 onUpdate(key, value/*, params*/) {
                     update_fired += 1;
                     assert.equal(key, 1);
-                    assert.deepEqual(value, {value: 7}); 
+                    assert.deepEqual(value, {value: 7});
                 },
                 onRemove() {},
                 onReset() {}
@@ -185,7 +192,7 @@ export function tests() {
             assert.equal(update_fired, 1);
         },
 
-        test_remove(assert) {
+        test_remove(assert): void {
             let fired = 0;
             const map = new ObservableMap<number, {value: number}>();
             const value = {value: 5};
@@ -194,7 +201,7 @@ export function tests() {
                 onRemove(key, value) {
                     fired += 1;
                     assert.equal(key, 1);
-                    assert.deepEqual(value, {value: 5}); 
+                    assert.deepEqual(value, {value: 5});
                 },
                 onAdd() {},
                 onUpdate() {},
@@ -205,7 +212,7 @@ export function tests() {
             assert.equal(fired, 1);
         },
 
-        test_iterate(assert) {
+        test_iterate(assert): void {
             const results: any[] = [];
             const map = new ObservableMap<number, {number: number}>();
             map.add(1, {number: 5});
@@ -219,11 +226,11 @@ export function tests() {
             assert.equal(results.find(([key]) => key === 2)[1].number, 6);
             assert.equal(results.find(([key]) => key === 3)[1].number, 7);
         },
-        test_size(assert) {
+        test_size(assert): void {
             const map = new ObservableMap<number, {number: number}>();
             map.add(1, {number: 5});
             map.add(2, {number: 6});
             assert.equal(map.size, 2);
         },
-    }
+    };
 }

src/observable/map/index.ts

@@ -0,0 +1,17 @@
+// In order to avoid a circular dependency problem at runtime between BaseObservableMap
+// and the classes that extend it, it's important that:
+//
+// 1) It always remain the first module exported below.
+// 2) Anything that imports any of the classes in this module
+//    ONLY import them from this index.ts file.
+//
+// See https://medium.com/visual-development/how-to-fix-nasty-circular-dependency-issues-once-and-for-all-in-javascript-typescript-a04c987cf0de
+// for more on why this discipline is necessary.
+export {BaseObservableMap} from './BaseObservableMap';
+export type {Mapper, Updater, Comparator, Filter} from './BaseObservableMap';
+export {ApplyMap} from './ApplyMap';
+export {FilteredMap} from './FilteredMap';
+export {JoinedMap} from './JoinedMap';
+export {LogMap} from './LogMap';
+export {MappedMap} from './MappedMap';
+export {ObservableMap} from './ObservableMap';