From 7611ea6033db64f1b0242bb0a07f274b15c322e5 Mon Sep 17 00:00:00 2001
From: Samuel Degueldre <sad@odoo.com>
Date: Fri, 18 Mar 2022 13:33:03 +0100
Subject: [PATCH] [FIX] reactivity: do not crash when reading reactive frozen
 objects

This crash was caused by the fact that Proxies *must* return the value of the
property on the target when that property is non-writeable and
non-configurable. Since the reactivity system always attempts to proxify the
value from the target, this crashes.

This commit fixes that by not proxifying such values. This however means that
from that point on, we have escaped the reactivity system and will not
subscribe to any changes in that object or its children.
---
 src/reactivity.ts        | 5 +++++
 tests/reactivity.test.ts | 7 +++++++
 2 files changed, 12 insertions(+)

diff --git a/src/reactivity.ts b/src/reactivity.ts
index 29937005..86aede0d 100644
--- a/src/reactivity.ts
+++ b/src/reactivity.ts
@@ -232,6 +232,11 @@ function basicProxyHandler<T extends Target>(callback: Callback): ProxyHandler<T
       if (key === TARGET) {
         return target;
       }
+      // non-writable non-configurable properties cannot be made reactive
+      const desc = Object.getOwnPropertyDescriptor(target, key);
+      if (desc && !desc.writable && !desc.configurable) {
+        return Reflect.get(target, key, proxy);
+      }
       observeTargetKey(target, key, callback);
       return possiblyReactive(Reflect.get(target, key, proxy), callback);
     },
diff --git a/tests/reactivity.test.ts b/tests/reactivity.test.ts
index 7647cf37..8a832024 100644
--- a/tests/reactivity.test.ts
+++ b/tests/reactivity.test.ts
@@ -1095,6 +1095,13 @@ describe("Reactivity", () => {
     expect(n).toBe(1);
     expect(state.k).toEqual({ n: 2 });
   });
+
+  test("can access properties on reactive of frozen objects", async () => {
+    const obj = Object.freeze({ a: {} });
+    const state = createReactive(obj);
+    expect(() => state.a).not.toThrow();
+    expect(state.a).toBe(obj.a);
+  });
 });
 
 describe("Collections", () => {