From 3892e4d36060ad6f1ddb4144d3eb017e0d95618b Mon Sep 17 00:00:00 2001
From: Stefan <steven.mirea@gmail.com>
Date: Wed, 21 Oct 2020 08:38:45 -0700
Subject: [PATCH 1/2] Proxy: Ignore setting a reference to itself. Fixes
 immerjs/immer#648

---
 src/core/proxy.ts | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/core/proxy.ts b/src/core/proxy.ts
index 2469d73e..bfa8049b 100644
--- a/src/core/proxy.ts
+++ b/src/core/proxy.ts
@@ -157,6 +157,9 @@ export const objectTraps: ProxyHandler<ProxyState> = {
 			prepareCopy(state)
 			markChanged(state)
 		}
+
+		if (state.copy_![prop] === value && typeof value !== "number") return true
+
 		// @ts-ignore
 		state.copy_![prop] = value
 		state.assigned_[prop] = true

From 462f50667cc9c9913822debd5b9d8a4d94cb7ea6 Mon Sep 17 00:00:00 2001
From: Stefan <steven.mirea@gmail.com>
Date: Tue, 17 Nov 2020 08:46:32 -0800
Subject: [PATCH 2/2] Added tests

---
 __tests__/patch.js | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/__tests__/patch.js b/__tests__/patch.js
index 7baba6e5..3cdf4bbd 100644
--- a/__tests__/patch.js
+++ b/__tests__/patch.js
@@ -1147,3 +1147,24 @@ test("#676 patching Date objects", () => {
 	)
 	expect(rebuilt.date).toEqual(new Date(2020, 10, 10, 8, 8, 8, 3))
 })
+
+test("#648 assigning object to itself should not change patches", () => {
+	const input = {
+		obj: {
+			value: 200
+		}
+	}
+
+	const [nextState, patches] = produceWithPatches(input, draft => {
+		draft.obj.value = 1
+		draft.obj = draft.obj
+	})
+
+	expect(patches).toEqual([
+		{
+			op: "replace",
+			path: ["obj", "value"],
+			value: 1
+		}
+	])
+})