From 555e3be69d39f4b35a312916253d9f38cbcab495 Mon Sep 17 00:00:00 2001
From: Adam Lewkowicz <37848894+alk831@users.noreply.github.com>
Date: Tue, 15 Oct 2019 22:44:14 +0200
Subject: [PATCH] types(watch): allow readonly arrays for watching multiple
 sources (#281)

---
 .../runtime-core/__tests__/apiWatch.spec.ts   | 22 +++++++++++++++++++
 packages/runtime-core/src/apiWatch.ts         |  2 +-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/packages/runtime-core/__tests__/apiWatch.spec.ts b/packages/runtime-core/__tests__/apiWatch.spec.ts
index 4ab13ddb..5f4dd323 100644
--- a/packages/runtime-core/__tests__/apiWatch.spec.ts
+++ b/packages/runtime-core/__tests__/apiWatch.spec.ts
@@ -103,6 +103,28 @@ describe('api: watch', () => {
     expect(dummy).toMatchObject([[2, 2, 3], [1, 1, 2]])
   })
 
+  it('watching multiple sources: readonly array', async () => {
+    const state = reactive({ count: 1 })
+    const status = ref(false)
+
+    let dummy
+    watch([() => state.count, status] as const, (vals, oldVals) => {
+      dummy = [vals, oldVals]
+      let [count] = vals
+      let [, oldStatus] = oldVals
+      // assert types
+      count + 1
+      oldStatus === true
+    })
+    await nextTick()
+    expect(dummy).toMatchObject([[1, false], []])
+
+    state.count++
+    status.value = false
+    await nextTick()
+    expect(dummy).toMatchObject([[2, false], [1, false]])
+  })
+
   it('stopping the watcher', async () => {
     const state = reactive({ count: 0 })
     let dummy
diff --git a/packages/runtime-core/src/apiWatch.ts b/packages/runtime-core/src/apiWatch.ts
index 50901a76..2127a4ee 100644
--- a/packages/runtime-core/src/apiWatch.ts
+++ b/packages/runtime-core/src/apiWatch.ts
@@ -56,7 +56,7 @@ export function watch<T>(
 ): StopHandle
 
 // overload #3: array of multiple sources + cb
-export function watch<T extends WatcherSource<unknown>[]>(
+export function watch<T extends readonly WatcherSource<unknown>[]>(
   sources: T,
   cb: (
     newValues: MapSources<T>,