Added defaultOptions and hardcoded two-level defaults nesting

gr2m · Jul 15, 2021 · e15a8fc · e15a8fc
1 parent 6af75f5
commit e15a8fc
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Showing 3 changed files with 121 additions and 18 deletions.
diff --git a/index.d.ts b/index.d.ts
@@ -31,6 +31,13 @@ declare type ReturnTypeOf<T extends AnyFunction | AnyFunction[]> =
     ? UnionToIntersection<Exclude<ReturnType<T[number]>, void>>
     : never;
 
+type ConstructorRequiringVersion<Class, PredefinedOptions> =
+  { defaultOptions: PredefinedOptions } & (
+    PredefinedOptions extends { version: string }
+      ? { new <NowProvided>(options?: NowProvided): Class & { options: NowProvided & PredefinedOptions }; }
+      : { new <NowProvided>(options: Base.Options & NowProvided): Class & { options: NowProvided & PredefinedOptions }; }
+  );
+
 export declare class Base<TOptions extends Base.Options = Base.Options> {
   static plugins: Plugin[];
 
@@ -75,18 +82,24 @@ export declare class Base<TOptions extends Base.Options = Base.Options> {
    * const base = new MyBase({ option: 'value' }); // `version` option is not required
    * base.options // typed as `{ version: string, otherDefault: string, option: string }`
    * ```
+   * @remarks
+   * Ideally, we would want to make this infinitely recursive: allowing any number of 
+   * .defaults({ ... }).defaults({ ... }).defaults({ ... }).defaults({ ... })...
+   * However, we don't see a clean way in today's TypeSript syntax to do so.
+   * We instead artificially limit accurate type inference to just three levels,
+   * since real users are not likely to go past that.
+   * @see https://github.com/gr2m/javascript-plugin-architecture-with-typescript-definitions/pull/57
    */
   static defaults<
-    TDefaults extends Base.Options,
-    S extends Constructor<Base<TDefaults>>
-  >(
-    this: S,
-    defaults: Partial<TDefaults>
-  ): {
-    new (...args: any[]): {
-      options: TDefaults;
-    };
-  } & S;
+    PredefinedOptionsOne,
+    Class extends Constructor<Base<Base.Options & PredefinedOptionsOne>>
+  >(this: Class, defaults: PredefinedOptionsOne): ConstructorRequiringVersion<Class, PredefinedOptionsOne> & {
+    defaults<PredefinedOptionsTwo>(this: Class, defaults: PredefinedOptionsTwo): ConstructorRequiringVersion<Class, PredefinedOptionsOne & PredefinedOptionsTwo> & {
+      defaults<PredefinedOptionsThree>(this: Class, defaults: PredefinedOptionsThree): ConstructorRequiringVersion<Class, PredefinedOptionsOne & PredefinedOptionsTwo & PredefinedOptionsThree> & Class;
+    } & Class;
+  } & Class;
+
+  static defaultOptions: {};
 
   /**
    * options passed to the constructor as constructor defaults

diff --git a/index.js b/index.js
@@ -14,13 +14,18 @@ export class Base {
       );
     };
   }
+
   static defaults(defaults) {
     return class extends this {
       constructor(...args) {
         super(Object.assign({}, defaults, args[0] || {}));
       }
+
+      static defaultOptions = defaults;
     };
   }
 
+  static defaultOptions = {};
+
   static plugins = [];
 }
diff --git a/index.test-d.ts b/index.test-d.ts
@@ -13,21 +13,105 @@ const base = new Base({
 // @ts-expect-error unknown properties cannot be used, see #31
 base.unknown;
 
-const BaseWithDefaults = Base.defaults({
+const BaseWithEmptyDefaults = Base.defaults({
   // there should be no required options
 });
 
-const FooBase = Base.plugin(fooPlugin).defaults({
-  default: "value",
+// 'version' is missing and should still be required
+// @ts-expect-error
+new BaseWithEmptyDefaults()
+
+// 'version' is missing and should still be required
+// @ts-expect-error
+new BaseWithEmptyDefaults({})
+
+const BaseLevelOne = Base.plugin(fooPlugin).defaults({
+  defaultOne: "value",
   version: "1.2.3",
 });
-const fooBase = new FooBase({
-  option: "value",
+
+// Because 'version' is already provided, this needs no argument
+new BaseLevelOne();
+new BaseLevelOne({});
+
+expectType<{
+  defaultOne: string,
+  version: string,
+}>(BaseLevelOne.defaultOptions);
+
+const baseLevelOne = new BaseLevelOne({
+  optionOne: "value",
 });
 
-expectType<string>(fooBase.options.default);
-expectType<string>(fooBase.options.option);
-expectType<string>(fooBase.foo);
+expectType<string>(baseLevelOne.options.defaultOne);
+expectType<string>(baseLevelOne.options.optionOne);
+expectType<string>(baseLevelOne.options.version);
+// @ts-expect-error unknown properties cannot be used, see #31
+baseLevelOne.unknown;
+
+const BaseLevelTwo = BaseLevelOne.defaults({
+  defaultTwo: 0,
+});
+
+expectType<{
+  defaultOne: string,
+  defaultTwo: number,
+  version: string,
+}>(BaseLevelTwo.defaultOptions);
+
+// Because 'version' is already provided, this needs no argument
+new BaseLevelTwo();
+new BaseLevelTwo({});
+
+// 'version' may be overriden, though it's not necessary
+new BaseLevelTwo({
+  version: 'new version',
+});
+
+const baseLevelTwo = new BaseLevelTwo({
+  optionTwo: true
+});
+
+expectType<number>(baseLevelTwo.options.defaultTwo);
+expectType<string>(baseLevelTwo.options.defaultOne);
+expectType<boolean>(baseLevelTwo.options.optionTwo);
+expectType<string>(baseLevelTwo.options.version);
+// @ts-expect-error unknown properties cannot be used, see #31
+baseLevelTwo.unknown;
+
+const BaseLevelThree = BaseLevelTwo.defaults({
+  defaultThree: ['a', 'b', 'c'],
+});
+
+expectType<{
+  defaultOne: string,
+  defaultTwo: number,
+  defaultThree: string[],
+  version: string,
+}>(BaseLevelThree.defaultOptions);
+
+// Because 'version' is already provided, this needs no argument
+new BaseLevelThree();
+new BaseLevelThree({});
+
+// Previous settings may be overriden, though it's not necessary
+new BaseLevelThree({
+  optionOne: '',
+  optionTwo: false,
+  version: 'new version',
+});
+
+const baseLevelThree = new BaseLevelThree({
+  optionThree: [0, 1, 2]
+});
+
+expectType<string>(baseLevelThree.options.defaultOne);
+expectType<number>(baseLevelThree.options.defaultTwo);
+expectType<string[]>(baseLevelThree.options.defaultThree);
+expectType<number[]>(baseLevelThree.options.optionThree);
+expectType<string>(baseLevelThree.options.version);
+// @ts-expect-error unknown properties cannot be used, see #31
+baseLevelThree.unknown;
 
 const BaseWithVoidPlugin = Base.plugin(voidPlugin);
 const baseWithVoidPlugin = new BaseWithVoidPlugin({
@@ -69,3 +153,4 @@ const baseWithOptionsPlugin = new BaseWithOptionsPlugin({
 });
 
 expectType<string>(baseWithOptionsPlugin.getFooOption());
+