Added ExtendBaseWith type for Rest API example

Author: JoshuaKGoldberg

examples/rest-api-client-dts/index.d.ts

@@ -1,9 +1,13 @@
-import { Base } from "../../index.js";
+import { Base, ExtendBaseWith } from "../../index.js";
 
 import { requestPlugin } from "./request-plugin.js";
 
-declare type Constructor<T> = new (...args: any[]) => T;
-
-export class RestApiClient extends Base {
-  request: ReturnType<typeof requestPlugin>["request"];
-}
+export const RestApiClient: ExtendBaseWith<
+  Base,
+  {
+    defaults: {
+      userAgent: string;
+    };
+    plugins: [typeof requestPlugin];
+  }
+>;

examples/rest-api-client-dts/index.test-d.ts

@@ -3,7 +3,9 @@ import { expectType } from "tsd";
 import { RestApiClient } from "./index.js";
 
 // @ts-expect-error - An argument for 'options' was not provided
-new RestApiClient();
+let value: typeof RestApiClient = new RestApiClient();
+
+expectType<{ userAgent: string }>(value.defaults);
 
 expectType<{ userAgent: string }>(RestApiClient.defaults);
 

index.d.ts

@@ -21,21 +21,23 @@ declare type UnionToIntersection<Union> = (
   ? Intersection
   : never;
 declare type AnyFunction = (...args: any) => any;
-declare type ReturnTypeOf<T extends AnyFunction | AnyFunction[]> =
-  T extends AnyFunction
-    ? ReturnType<T>
-    : T extends AnyFunction[]
-    ? UnionToIntersection<Exclude<ReturnType<T[number]>, void>>
-    : never;
+declare type ReturnTypeOf<
+  T extends AnyFunction | AnyFunction[]
+> = T extends AnyFunction
+  ? ReturnType<T>
+  : T extends AnyFunction[]
+  ? UnionToIntersection<Exclude<ReturnType<T[number]>, void>>
+  : never;
 
 type ClassWithPlugins = Constructor<any> & {
   plugins: Plugin[];
 };
 
-type RemainingRequirements<PredefinedOptions> =
-  keyof PredefinedOptions extends never
-    ? Base.Options
-    : Omit<Base.Options, keyof PredefinedOptions>;
+type RemainingRequirements<
+  PredefinedOptions
+> = keyof PredefinedOptions extends never
+  ? Base.Options
+  : Omit<Base.Options, keyof PredefinedOptions>;
 
 type NonOptionalKeys<Obj> = {
   [K in keyof Obj]: {} extends Pick<Obj, K> ? undefined : K;
@@ -51,10 +53,7 @@ type RequiredIfRemaining<PredefinedOptions, NowProvided> = NonOptionalKeys<
         NowProvided
     ];
 
-type ConstructorRequiringOptionsIfNeeded<
-  Class extends ClassWithPlugins,
-  PredefinedOptions
-> = {
+type ConstructorRequiringOptionsIfNeeded<Class, PredefinedOptions> = {
   defaults: PredefinedOptions;
 } & {
   new <NowProvided>(
@@ -156,4 +155,30 @@ export declare class Base<TOptions extends Base.Options = Base.Options> {
 
   constructor(options: TOptions);
 }
+
+type Extensions = {
+  defaults?: {};
+  plugins?: Plugin[];
+};
+
+type OrObject<T, Extender> = T extends Extender ? {} : T;
+
+type ApplyPlugins<
+  Plugins extends Plugin[] | undefined
+> = Plugins extends Plugin[]
+  ? UnionToIntersection<ReturnType<Plugins[number]>>
+  : {};
+
+export type ExtendBaseWith<
+  BaseClass extends Base,
+  BaseExtensions extends Extensions
+> = BaseClass &
+  ConstructorRequiringOptionsIfNeeded<
+    BaseClass & ApplyPlugins<BaseExtensions["plugins"]>,
+    OrObject<BaseClass["options"], unknown>
+  > &
+  ApplyPlugins<BaseExtensions["plugins"]> & {
+    defaults: OrObject<BaseExtensions["defaults"], undefined>;
+  };
+
 export {};

index.test-d.ts

@@ -1,5 +1,5 @@
 import { expectType } from "tsd";
-import { Base, Plugin } from "./index.js";
+import { Base, ExtendBaseWith, Plugin } from "./index.js";
 
 import { fooPlugin } from "./plugins/foo/index.js";
 import { barPlugin } from "./plugins/bar/index.js";
@@ -229,12 +229,58 @@ expectType<{
   defaultThree: string[];
 }>({ ...BaseWithManyChainedDefaultsAndPlugins.defaults });
 
-const baseWithManyChainedDefaultsAndPlugins =
-  new BaseWithManyChainedDefaultsAndPlugins({
+const baseWithManyChainedDefaultsAndPlugins = new BaseWithManyChainedDefaultsAndPlugins(
+  {
     required: "1.2.3",
     foo: "bar",
-  });
+  }
+);
 
 expectType<string>(baseWithManyChainedDefaultsAndPlugins.foo);
 expectType<string>(baseWithManyChainedDefaultsAndPlugins.bar);
 expectType<string>(baseWithManyChainedDefaultsAndPlugins.getFooOption());
+
+declare const RestApiClient: ExtendBaseWith<
+  Base,
+  {
+    defaults: {
+      defaultValue: string;
+    };
+    plugins: [
+      () => { pluginValueOne: number },
+      () => { pluginValueTwo: boolean }
+    ];
+  }
+>;
+
+expectType<string>(RestApiClient.defaults.defaultValue);
+
+// @ts-expect-error
+RestApiClient.defaults.unexpected;
+
+expectType<number>(RestApiClient.pluginValueOne);
+expectType<boolean>(RestApiClient.pluginValueTwo);
+
+// @ts-expect-error
+RestApiClient.unexpected;
+
+declare const MoreDefaultRestApiClient: ExtendBaseWith<
+  typeof RestApiClient,
+  {
+    defaults: {
+      anotherDefaultValue: number;
+    };
+  }
+>;
+
+expectType<string>(MoreDefaultRestApiClient.defaults.defaultValue);
+expectType<number>(MoreDefaultRestApiClient.defaults.anotherDefaultValue);
+
+declare const MorePluginRestApiClient: ExtendBaseWith<
+  typeof MoreDefaultRestApiClient,
+  {
+    plugins: [() => { morePluginValue: string[] }];
+  }
+>;
+
+expectType<string[]>(MorePluginRestApiClient.morePluginValue);