Apply more strict typescript around the codebase (#2778)

* Apply more strict typescript around the codebase

* Fix tests

* Revert strict mode commit

* Iterate strict

* Iterate

* Iterate strict

* Iterate

* Fix tests

* Iterate

* Iterate strict

* Add tests

* Iterate

* Iterate

* Fix tests

* Fix tests

* Strict types be strict

* Fix types

* detectOpenHandles

* Strict

* Fix client not stopping

* Add sync peeking tests

* Make test happier

* More strict

* Iterate

* Stabilise

* Moar strictness

* Improve coverage

* Fix types

* Fix types

* Improve types further

* Fix types

* Improve typing of NamespacedValue

* Fix types

src/errors.ts

@@ -0,0 +1,51 @@
+/*
+Copyright 2022 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.
+*/
+
+export enum InvalidStoreState {
+    ToggledLazyLoading,
+}
+
+export class InvalidStoreError extends Error {
+    public static TOGGLED_LAZY_LOADING = InvalidStoreState.ToggledLazyLoading;
+
+    public constructor(public readonly reason: InvalidStoreState, public readonly value: any) {
+        const message = `Store is invalid because ${reason}, ` +
+            `please stop the client, delete all data and start the client again`;
+        super(message);
+        this.name = "InvalidStoreError";
+    }
+}
+
+export enum InvalidCryptoStoreState {
+    TooNew = "TOO_NEW",
+}
+
+export class InvalidCryptoStoreError extends Error {
+    public static TOO_NEW = InvalidCryptoStoreState.TooNew;
+
+    public constructor(public readonly reason: InvalidCryptoStoreState) {
+        const message = `Crypto store is invalid because ${reason}, ` +
+            `please stop the client, delete all data and start the client again`;
+        super(message);
+        this.name = 'InvalidCryptoStoreError';
+    }
+}
+
+export class KeySignatureUploadError extends Error {
+    public constructor(message: string, public readonly value: any) {
+        super(message);
+    }
+}