Merge default{State,Config} with constructor options initial{State,Config}

- Previous code is inconsistent with jsdoc description: "Both initial state and initial configuration options are merged with defaults upon initialization."
- Generic spread expressions for object literals are supported by TypeScript: microsoft/TypeScript#28234

Author: MajorLift

packages/base-controller/CHANGELOG.md

@@ -9,7 +9,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
-- **BREAKING:** Convert `BaseConfig`, `BaseState` interfaces to types.
+- **BREAKING:** The `initialize` method of the `BaseControllerV1` class now merges the `initialState`, `initialConfig` constructor options with `defaultState`, `defaultConfig` before assigning the results to `internalState`, `internalConfig`, instead of simply assigning the defaults ([#3959](https://github.com/MetaMask/core/pull/3959))
+- **BREAKING:** Convert `BaseConfig`, `BaseState` interfaces to types ([#3959](https://github.com/MetaMask/core/pull/3959))
   - As types, `BaseConfig`, `BaseState` now extend `Record` and have an index signature of `string`.
 
 ## [4.1.1]

packages/base-controller/src/BaseControllerV1.ts

@@ -71,6 +71,8 @@ export class BaseControllerV1<C extends BaseConfig, S extends BaseState> {
    * @param state - Initial state to set on this controller.
    */
   constructor(config: Partial<C> = {}, state: Partial<S> = {}) {
+    this.initialState = { ...(state as S) };
+    this.initialConfig = { ...(config as C) };
   }
 
   /**
@@ -81,8 +83,8 @@ export class BaseControllerV1<C extends BaseConfig, S extends BaseState> {
    * @returns This controller instance.
    */
   protected initialize() {
-    this.internalState = this.defaultState;
-    this.internalConfig = this.defaultConfig;
+    this.internalState = { ...this.defaultState, ...this.initialState };
+    this.internalConfig = { ...this.defaultConfig, ...this.initialConfig };
     this.configure(this.initialConfig);
     this.update(this.initialState);
     return this;