From 4bfbc6b31a700abb062c23cc09c6efcce109a278 Mon Sep 17 00:00:00 2001
From: Ben Kraft <benkraft@makenotion.com>
Date: Tue, 31 Jan 2023 14:19:08 -0800
Subject: [PATCH] feat(@jest/expect): Expose type of actual to Matchers

Matchers isn't as typed as some users would like (see #13334, #13812).
For users who want to customize it by extending the `Matchers`
interface, it's useful to have access to the type of `actual` (the
argument of `expect`) so you can do, say,
```ts
interface Matchers<R, T> {
    toTypedEqual(expected: T): R
}
```
This commit exposes it. The first-party matchers still have the same
types as before.
---
 CHANGELOG.md                      | 2 ++
 packages/expect/src/types.ts      | 2 +-
 packages/jest-expect/src/types.ts | 2 +-
 3 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4997b655331c..5ac9e1680043 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 ### Features
 
+- `[@jest/expect]` provide type of `actual` as a generic argument to `Matchers` to allow better-typed extensions (#TBD)
+
 ### Fixes
 
 ### Chore & Maintenance
diff --git a/packages/expect/src/types.ts b/packages/expect/src/types.ts
index f3687b5597cb..3803d1e251b4 100644
--- a/packages/expect/src/types.ts
+++ b/packages/expect/src/types.ts
@@ -134,7 +134,7 @@ type PromiseMatchers = {
   resolves: Matchers<Promise<void>> & Inverse<Matchers<Promise<void>>>;
 };
 
-export interface Matchers<R extends void | Promise<void>> {
+export interface Matchers<R extends void | Promise<void>, T = unknown> {
   /**
    * Ensures the last call to a mock function was provided specific args.
    */
diff --git a/packages/jest-expect/src/types.ts b/packages/jest-expect/src/types.ts
index 10739da8481e..d1ba64a7f66f 100644
--- a/packages/jest-expect/src/types.ts
+++ b/packages/jest-expect/src/types.ts
@@ -29,7 +29,7 @@ type Inverse<Matchers> = {
   not: Matchers;
 };
 
-type JestMatchers<R extends void | Promise<void>, T> = Matchers<R> &
+type JestMatchers<R extends void | Promise<void>, T> = Matchers<R, T> &
   SnapshotMatchers<R, T>;
 
 type PromiseMatchers<T = unknown> = {