From c7953e288ae14ff157370c9a89a08703e72ddd12 Mon Sep 17 00:00:00 2001
From: Benny Yen <benny123tw@gmail.com>
Date: Wed, 2 Apr 2025 09:52:21 +0000
Subject: [PATCH] fix: update `then` method signature

---
 src/p.test.ts |  9 ++++++++-
 src/p.ts      | 11 +++++------
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/src/p.test.ts b/src/p.test.ts
index 33c39f6..26a943a 100644
--- a/src/p.test.ts
+++ b/src/p.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest'
+import { describe, expect, expectTypeOf, it } from 'vitest'
 import { p as P } from './p'
 
 const timeout = (ms: number) => new Promise(resolve => setTimeout(resolve, ms))
@@ -71,4 +71,11 @@ describe('should', () => {
       expect(e).toBeInstanceOf(TypeError)
     }
   })
+
+  it('should return the correct type', async () => {
+    const p = P([1, 2, 3])
+    expectTypeOf(await p).toEqualTypeOf<number[]>()
+    // @see issue #47
+    expectTypeOf(await p.map(async i => i).map(async i => i)).toEqualTypeOf<number[]>()
+  })
 })
diff --git a/src/p.ts b/src/p.ts
index 752aa40..3772731 100644
--- a/src/p.ts
+++ b/src/p.ts
@@ -79,12 +79,11 @@ class PInstance<T = any> extends Promise<Awaited<T>[]> {
     this.promises.clear()
   }
 
-  then(fn?: () => PromiseLike<any>) {
-    const p = this.promise
-    if (fn)
-      return p.then(fn)
-    else
-      return p
+  then<TResult1 = Awaited<T>[], TResult2 = never>(
+    onfulfilled?: ((value: Awaited<T>[]) => TResult1 | PromiseLike<TResult1>) | null,
+    onrejected?: ((reason: any) => TResult2 | PromiseLike<TResult2>) | null,
+  ) {
+    return this.promise.then(onfulfilled, onrejected)
   }
 
   catch(fn?: (err: unknown) => PromiseLike<any>) {