feat(typescript): Inherit options types set in Base.defaults() (#33) thanks @jacobwgillespie

Author: gr2m

package.json

@@ -6,7 +6,9 @@
   "types": "./index.d.ts",
   "scripts": {
     "build": "tsc src/index.ts --declaration --outDir .",
-    "test": "jest --coverage"
+    "test": "npm run -s test:code && npm run -s test:typescript",
+    "test:code": "jest --coverage",
+    "test:typescript": "npx tsc --noEmit --declaration --noUnusedLocals test-typescript.ts"
   },
   "repository": "github:gr2m/javascript-plugin-architecture-with-typescript-definitions",
   "keywords": [

src/index.ts

@@ -27,7 +27,7 @@ type ReturnTypeOf<T extends AnyFunction | AnyFunction[]> = T extends AnyFunction
   ? UnionToIntersection<ReturnType<T[number]>>
   : never;
 
-export class Base {
+export class Base<TOptions extends Options = Options> {
   static plugins: TestPlugin[] = [];
   static plugin<
     S extends Constructor<any> & { plugins: any[] },
@@ -46,21 +46,25 @@ export class Base {
       );
     };
 
-    return BaseWithPlugins as typeof this & { plugins: any[] } &
-      Constructor<UnionToIntersection<ReturnTypeOf<T1> & ReturnTypeOf<T2>>>;
+    return BaseWithPlugins as typeof this & { plugins: any[] } & Constructor<
+        UnionToIntersection<ReturnTypeOf<T1> & ReturnTypeOf<T2>>
+      >;
   }
 
-  static defaults<S extends Constructor<any>>(this: S, defaults: Options) {
+  static defaults<
+    TDefaults extends Options,
+    S extends Constructor<Base<TDefaults>>
+  >(this: S, defaults: TDefaults) {
     const BaseWitDefaults = class extends this {
       constructor(...args: any[]) {
         super(Object.assign({}, defaults, args[0] || {}));
       }
     };
 
-    return BaseWitDefaults as typeof this;
+    return BaseWitDefaults as typeof BaseWitDefaults & typeof this;
   }
 
-  constructor(options: Options = {}) {
+  constructor(options: TOptions = {} as TOptions) {
     this.options = options;
 
     // apply plugins
@@ -71,5 +75,5 @@ export class Base {
     });
   }
 
-  options: Options;
-}
+  options: TOptions;
+}

test-typescript.ts

@@ -0,0 +1,22 @@
+// ************************************************************
+// THIS CODE IS NOT EXECUTED. IT IS JUST FOR TYPECHECKING
+// ************************************************************
+
+import { Base } from "./src";
+
+function isString(what: string) {}
+
+// sets .options types from constructor options
+const base = new Base({ option: "value" });
+isString(base.options.option);
+
+// sets .options types from Base.defaults({})
+const BaseWithDefaults = Base.defaults({ parentOption: "value" });
+const baseWithDefaults = new BaseWithDefaults({ childOption: "value" });
+
+isString(baseWithDefaults.options.childOption);
+// see #32
+isString(baseWithDefaults.options.parentOption);
+
+// @ts-expect-error see #31
+baseWithDefaults.unknown;