Use unknown rather than any for BaseController state (#365)

* Use `unknown` rather than `any` for BaseController state

The BaseController state now uses `unknown` rather than `any` as the
type for state properties. `unknown` is more type-safe than `any` in
cases like this where we don't know what type to expect. See here for
details [1].

This was suggested by @rekmarks during review of #362 [2].

[1]: microsoft/TypeScript#24439
[2]: #362 (comment)

* Use type alias for controller state rather than interface

The mock controller state in the base controller tests now uses a type
alias for the controller state rather than an interface. This was
required to get around an incompatibility between
`Record<string, unknown>` and interfaces[1].

The `@typescript-eslint/consistent-type-definitions` ESLint rule has
been disabled, as this problem will be encountered fairly frequently.

[1]: microsoft/TypeScript#15300 (comment)

Author: Gudahtt

.eslintrc.js

@@ -25,6 +25,9 @@ module.exports = {
     'no-shadow': 'off',
     '@typescript-eslint/no-shadow': 'error',
     '@typescript-eslint/indent': 'off',
+    // disabled due to incompatibility with Record<string, unknown>
+    // See https://github.com/Microsoft/TypeScript/issues/15300#issuecomment-702872440
+    '@typescript-eslint/consistent-type-definitions': 'off',
 
     // TODO re-enable most of these rules
     '@typescript-eslint/no-non-null-assertion': 'off',

src/BaseControllerV2.test.ts

@@ -3,9 +3,9 @@ import * as sinon from 'sinon';
 
 import { BaseController } from './BaseControllerV2';
 
-interface MockControllerState {
+type MockControllerState = {
   count: number;
-}
+};
 
 class MockController extends BaseController<MockControllerState> {
   update(callback: (state: Draft<MockControllerState>) => void | MockControllerState) {

src/BaseControllerV2.ts

@@ -14,7 +14,7 @@ export type Listener<T> = (state: T, patches: Patch[]) => void;
 /**
  * Controller class that provides state management and subscriptions
  */
-export class BaseController<S extends Record<string, any>> {
+export class BaseController<S extends Record<string, unknown>> {
   private internalState: S;
 
   private internalListeners: Set<Listener<S>> = new Set();