From 205419a1313f2549f2490b8a8b7dbb746b61866f Mon Sep 17 00:00:00 2001
From: Gregor Martynus <39992+gr2m@users.noreply.github.com>
Date: Fri, 18 Jun 2021 10:28:02 -0700
Subject: [PATCH 1/2] feat: extend `Base` constructor options with plugins

---
 index.test-d.ts                 |  6 ++++++
 plugins/with-options/index.d.ts | 10 ++++++++++
 plugins/with-options/index.js   | 11 +++++++++++
 3 files changed, 27 insertions(+)
 create mode 100644 plugins/with-options/index.d.ts
 create mode 100644 plugins/with-options/index.js

diff --git a/index.test-d.ts b/index.test-d.ts
index f8fcddc..dc522d0 100644
--- a/index.test-d.ts
+++ b/index.test-d.ts
@@ -4,6 +4,7 @@ import { Base } from "./index.js";
 import { fooPlugin } from "./plugins/foo/index.js";
 import { barPlugin } from "./plugins/bar/index.js";
 import { voidPlugin } from "./plugins/void/index.js";
+import { withOptionsPlugin } from "./plugins/with-options";
 
 const base = new Base();
 
@@ -48,3 +49,8 @@ expectType<string>(baseWithVoidAndNonVoidPlugins.bar);
 
 // @ts-expect-error unknown properties cannot be used, see #31
 baseWithVoidAndNonVoidPlugins.unknown;
+
+const BaseWithOptionsPlugin = Base.plugin(withOptionsPlugin);
+const baseWithOptionsPlugin = new BaseWithOptionsPlugin();
+
+expectType<string>(baseWithOptionsPlugin.getFooOption());
diff --git a/plugins/with-options/index.d.ts b/plugins/with-options/index.d.ts
new file mode 100644
index 0000000..4214b68
--- /dev/null
+++ b/plugins/with-options/index.d.ts
@@ -0,0 +1,10 @@
+import { Base } from "../..";
+
+// TODO: add "foo" to Base.Options type
+
+export function withOptionsPlugin(
+  base: Base,
+  options: Base.Options
+): {
+  getFooOption: () => Base.Options["foo"];
+};
diff --git a/plugins/with-options/index.js b/plugins/with-options/index.js
new file mode 100644
index 0000000..23b84de
--- /dev/null
+++ b/plugins/with-options/index.js
@@ -0,0 +1,11 @@
+/**
+ * @param {import('../..').Base} base
+ * @param {import('../..').Base.Options} options
+ */
+export function withOptionsPlugin(base, options) {
+  return {
+    getFooOption() {
+      return options.foo;
+    },
+  };
+}

From cb11cc919f2e837234cfc6938d17873947860db0 Mon Sep 17 00:00:00 2001
From: Gregor Martynus <39992+gr2m@users.noreply.github.com>
Date: Fri, 18 Jun 2021 13:22:03 -0700
Subject: [PATCH 2/2] feat: extend `Base` constructor options with plugins

---
 index.d.ts                      |  6 +++---
 plugins/with-options/index.d.ts | 11 +++++++++--
 plugins/with-options/index.js   |  2 +-
 3 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/index.d.ts b/index.d.ts
index 8a920c8..6489eb8 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -1,7 +1,7 @@
-export declare namespace Base {
-  type Options = {
+export namespace Base {
+  interface Options {
     [key: string]: unknown;
-  };
+  }
 }
 
 declare type ApiExtension = {
diff --git a/plugins/with-options/index.d.ts b/plugins/with-options/index.d.ts
index 4214b68..7d97f99 100644
--- a/plugins/with-options/index.d.ts
+++ b/plugins/with-options/index.d.ts
@@ -1,10 +1,17 @@
+// https://www.typescriptlang.org/docs/handbook/declaration-files/templates/module-plugin-d-ts.html
 import { Base } from "../..";
 
-// TODO: add "foo" to Base.Options type
+declare module "../.." {
+  namespace Base {
+    interface Options {
+      foo?: string;
+    }
+  }
+}
 
 export function withOptionsPlugin(
   base: Base,
   options: Base.Options
 ): {
-  getFooOption: () => Base.Options["foo"];
+  getFooOption: () => Required<Base.Options>["foo"];
 };
diff --git a/plugins/with-options/index.js b/plugins/with-options/index.js
index 23b84de..7decc7d 100644
--- a/plugins/with-options/index.js
+++ b/plugins/with-options/index.js
@@ -5,7 +5,7 @@
 export function withOptionsPlugin(base, options) {
   return {
     getFooOption() {
-      return options.foo;
+      return options.foo || "my default";
     },
   };
 }