fix: avoid base to be set to an intersection with void if a plugin returns void (#53)

Author: gr2m

index.d.ts

@@ -21,7 +21,7 @@ declare type ReturnTypeOf<T extends AnyFunction | AnyFunction[]> =
   T extends AnyFunction
     ? ReturnType<T>
     : T extends AnyFunction[]
-    ? UnionToIntersection<ReturnType<T[number]>>
+    ? UnionToIntersection<Exclude<ReturnType<T[number]>, void>>
     : never;
 
 export declare class Base<TOptions extends Options = Options> {

index.test-d.ts

@@ -3,20 +3,56 @@ import { Base } from "./index.js";
 
 const fooPlugin = () => {
   return {
-    foo: () => "foo",
+    foo: "foo",
   };
 };
+const barPlugin = () => {
+  return {
+    bar: "bar",
+  };
+};
+
+const voidPlugin = () => {
+  // returns void
+};
+
+const base = new Base();
+
+// @ts-expect-error unknown properties cannot be used, see #31
+base.unknown;
 
-const MyBase = Base.plugin(fooPlugin).defaults({
+const FooBase = Base.plugin(fooPlugin).defaults({
   default: "value",
 });
-const base = new MyBase({
+const fooBase = new FooBase({
   option: "value",
 });
 
-expectType<string>(base.options.default);
-expectType<string>(base.options.option);
-expectType<string>(base.foo());
+expectType<string>(fooBase.options.default);
+expectType<string>(fooBase.options.option);
+expectType<string>(fooBase.foo);
+
+const BaseWithVoidPlugin = Base.plugin(voidPlugin);
+const baseWithVoidPlugin = new BaseWithVoidPlugin();
 
 // @ts-expect-error unknown properties cannot be used, see #31
-base.unknown;
+baseWithVoidPlugin.unknown;
+
+const BaseWithFooAndBarPlugins = Base.plugin(barPlugin, fooPlugin);
+const baseWithFooAndBarPlugins = new BaseWithFooAndBarPlugins();
+
+expectType<string>(baseWithFooAndBarPlugins.foo);
+expectType<string>(baseWithFooAndBarPlugins.bar);
+
+// @ts-expect-error unknown properties cannot be used, see #31
+baseWithFooAndBarPlugins.unknown;
+
+const BaseWithVoidAndNonVoidPlugins = Base.plugin(
+  barPlugin,
+  voidPlugin,
+  fooPlugin
+);
+const baseWithVoidAndNonVoidPlugins = new BaseWithVoidAndNonVoidPlugins();
+
+expectType<string>(baseWithVoidAndNonVoidPlugins.foo);
+expectType<string>(baseWithVoidAndNonVoidPlugins.bar);