Add assertion for Ember.A modifying behavior

Author: wagenet

packages/@ember/-internals/runtime/tests/system/native_array/a_test.js

@@ -47,5 +47,14 @@ moduleFor(
       proxy.pushObjects([4, 5]);
       assert.deepEqual(original, [1, 2, 3, 4, 5], 'pushObjects works');
     }
+
+    ['@test Ember.A adds warnings about modification to original']() {
+      let original = [1, 2];
+      A(original);
+
+      expectAssertion(() => {
+        original.pushObject(1);
+      });
+    }
   }
 );

packages/@ember/array/index.ts

@@ -2051,6 +2051,19 @@ interface EmberAProxy<T = unknown> extends NativeArray<T> {}
 // Ensure instanceof works correctly
 Object.setPrototypeOf(EmberAProxy.prototype, Array.prototype);
 
+const nativeArrayThrowers = Object.fromEntries(
+  Array.from(NativeArray.keys()).map((key) => {
+    return [
+      key,
+      () =>
+        assert(
+          `Ember.A was incorrectly modifying the original array. Do not call the EmberArray function ${key} on the original array. Instead, call it on the value returned by Ember.A.`
+        ),
+    ];
+  })
+);
+const ModifiedNativeArray = Mixin.create(nativeArrayThrowers);
+
 let A: <T>(arr?: Array<T>) => NativeArray<T>;
 
 if (ENV.EXTEND_PROTOTYPES.Array) {
@@ -2076,6 +2089,12 @@ if (ENV.EXTEND_PROTOTYPES.Array) {
       // SAFETY: If it's a true native array and it is also an EmberArray then it should be an Ember NativeArray
       return arr as NativeArray<T>;
     } else {
+      // Remove this in Ember 5.0.
+      if (DEBUG) {
+        if (arr) {
+          ModifiedNativeArray.apply(arr);
+        }
+      }
       return new EmberAProxy(arr ?? []);
     }
   };