fix: type-widening bug when handling plugins. (#53)

README.md

@@ -342,7 +342,7 @@ See [before-after-hook](https://github.com/gr2m/before-after-hook#readme) for
 
 ## Plugins
 
-Octokit’s functionality can be extended using plugins. THe `Octokit.plugin()` method accepts a function or an array of functions and returns a new constructor.
+Octokit’s functionality can be extended using plugins. The `Octokit.plugin()` method accepts a plugin (or many) and returns a new constructor.
 
 A plugin is a function which gets two arguments:
 
@@ -353,10 +353,10 @@ In order to extend `octokit`'s API, the plugin must return an object with the ne
 
 ```js
 // index.js
-const MyOctokit = require("@octokit/core").plugin([
+const MyOctokit = require("@octokit/core").plugin(
   require("./lib/my-plugin"),
   require("octokit-plugin-example")
-]);
+);
 
 const octokit = new MyOctokit({ greeting: "Moin moin" });
 octokit.helloWorld(); // logs "Moin moin, world!"
@@ -388,11 +388,11 @@ You can build your own Octokit class with preset default options and plugins. In
 
 ```js
 const MyActionOctokit = require("@octokit/core")
-  .plugin([
+  .plugin(
     require("@octokit/plugin-paginate"),
     require("@octokit/plugin-throttle"),
-    require("@octokit/plugin-retry"),
-  ])
+    require("@octokit/plugin-retry")
+  )
   .defaults({
     authStrategy: require("@octokit/auth-action"),
     userAgent: `my-octokit-action/v1.2.3`,

src/index.ts

@@ -10,6 +10,7 @@ import {
   OctokitPlugin,
   RequestParameters,
   ReturnTypeOf,
+  UnionToIntersection,
 } from "./types";
 import { VERSION } from "./version";
 
@@ -42,22 +43,43 @@ export class Octokit {
   }
 
   static plugins: OctokitPlugin[] = [];
+  /**
+   * Attach a plugin (or many) to your Octokit instance.
+   *
+   * @example
+   * const API = Octokit.plugin(plugin1, plugin2, plugin3, ...)
+   */
   static plugin<
     S extends Constructor<any> & { plugins: any[] },
-    T extends OctokitPlugin | OctokitPlugin[]
-  >(this: S, pluginOrPlugins: T) {
+    T1 extends OctokitPlugin | OctokitPlugin[],
+    T2 extends OctokitPlugin[]
+  >(this: S, p1: T1, ...p2: T2) {
+    if (p1 instanceof Array) {
+      console.warn(
+        [
+          "Passing an array of plugins to Octokit.plugin() has been deprecated.",
+          "Instead of:",
+          "  Octokit.plugin([plugin1, plugin2, ...])",
+          "Use:",
+          "  Octokit.plugin(plugin1, plugin2, ...)",
+        ].join("\n")
+      );
+    }
     const currentPlugins = this.plugins;
-    const newPlugins = Array.isArray(pluginOrPlugins)
-      ? pluginOrPlugins
-      : [pluginOrPlugins];
-
+    let newPlugins: (OctokitPlugin | undefined)[] = [
+      ...(p1 instanceof Array
+        ? (p1 as OctokitPlugin[])
+        : [p1 as OctokitPlugin]),
+      ...p2,
+    ];
     const NewOctokit = class extends this {
       static plugins = currentPlugins.concat(
         newPlugins.filter((plugin) => !currentPlugins.includes(plugin))
       );
     };
 
-    return NewOctokit as typeof NewOctokit & Constructor<ReturnTypeOf<T>>;
+    return NewOctokit as typeof NewOctokit &
+      Constructor<UnionToIntersection<ReturnTypeOf<T1> & ReturnTypeOf<T2>>>;
   }
 
   constructor(options: OctokitOptions = {}) {

src/types.ts

@@ -28,7 +28,7 @@ export type ReturnTypeOf<
  * @author https://stackoverflow.com/users/2887218/jcalz
  * @see https://stackoverflow.com/a/50375286/10325032
  */
-type UnionToIntersection<Union> = (
+export type UnionToIntersection<Union> = (
   Union extends any ? (argument: Union) => void : never
 ) extends (argument: infer Intersection) => void // tslint:disable-line: no-unused
   ? Intersection

test/__snapshots__/plugin.test.ts.snap

@@ -0,0 +1,21 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`Octokit.plugin() supports array of plugins and warns of deprecated usage 1`] = `
+[MockFunction] {
+  "calls": Array [
+    Array [
+      "Passing an array of plugins to Octokit.plugin() has been deprecated.
+Instead of:
+  Octokit.plugin([plugin1, plugin2, ...])
+Use:
+  Octokit.plugin(plugin1, plugin2, ...)",
+    ],
+  ],
+  "results": Array [
+    Object {
+      "type": "return",
+      "value": undefined,
+    },
+  ],
+}
+`;

test/plugin.test.ts

@@ -1,41 +1,43 @@
 import { Octokit } from "../src";
 
+const pluginFoo = () => {
+  return { foo: "bar" };
+};
+const pluginBaz = () => {
+  return { baz: "daz" };
+};
+const pluginQaz = () => {
+  return { qaz: "naz" };
+};
+
 describe("Octokit.plugin()", () => {
   it("gets called in constructor", () => {
-    const MyOctokit = Octokit.plugin(() => {
-      return {
-        foo: "bar",
-      };
-    });
+    const MyOctokit = Octokit.plugin(pluginFoo);
     const myClient = new MyOctokit();
     expect(myClient.foo).toEqual("bar");
   });
 
-  it("supports array of plugins", () => {
-    const MyOctokit = Octokit.plugin([
-      () => {
-        return {
-          foo: "bar",
-        };
-      },
-      () => {
-        return { baz: "daz" };
-      },
-    ]);
+  it("supports array of plugins and warns of deprecated usage", () => {
+    const warningSpy = jest.spyOn(console, "warn").mockImplementation();
+    const MyOctokit = Octokit.plugin([pluginFoo, pluginBaz]);
     const myClient = new MyOctokit();
     expect(myClient.foo).toEqual("bar");
     expect(myClient.baz).toEqual("daz");
+    expect(warningSpy).toMatchSnapshot();
+    warningSpy.mockClear();
   });
 
+  it("supports multiple plugins", () => {
+    const MyOctokit = Octokit.plugin(pluginFoo, pluginBaz, pluginQaz);
+    const myClient = new MyOctokit();
+    expect(myClient.foo).toEqual("bar");
+    expect(myClient.baz).toEqual("daz");
+    expect(myClient.qaz).toEqual("naz");
+  });
   it("does not override plugins of original constructor", () => {
-    const MyOctokit = Octokit.plugin((octokit) => {
-      return {
-        foo: "bar",
-      };
-    });
+    const MyOctokit = Octokit.plugin(pluginFoo);
     const myClient = new MyOctokit();
     expect(myClient.foo).toEqual("bar");
-
     const octokit = new Octokit();
     expect(octokit).not.toHaveProperty("foo");
   });
@@ -64,17 +66,9 @@ describe("Octokit.plugin()", () => {
   });
 
   it("supports chaining", () => {
-    const MyOctokit = Octokit.plugin(() => {
-      return {
-        foo: "bar",
-      };
-    })
-      .plugin(() => {
-        return { baz: "daz" };
-      })
-      .plugin(() => {
-        return { qaz: "naz" };
-      });
+    const MyOctokit = Octokit.plugin(pluginFoo)
+      .plugin(pluginBaz)
+      .plugin(pluginQaz);
 
     const myClient = new MyOctokit();
     expect(myClient.foo).toEqual("bar");