[GR-51680] Add regression test.

graal-js/src/com.oracle.truffle.js.test/js/GR-51680.js

@@ -0,0 +1,80 @@
+/*
+ * Copyright (c) 2024, 2024, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * Licensed under the Universal Permissive License v 1.0 as shown at http://oss.oracle.com/licenses/upl.
+ */
+
+/**
+ * Regression test checking successful transition from sealed JSObjectArray to ObjectArray strategy.
+ *
+ * @option debug-builtin
+ */
+
+load("assert.js");
+
+const o = {};
+const x = 42;
+
+for (const jsobjectArrayType of ["ZeroBasedJSObjectArray", "ContiguousJSObjectArray", "HolesJSObjectArray"]) {
+  const objectArrayType = jsobjectArrayType.replace("JS", "");
+  switch (jsobjectArrayType) {
+    case "ZeroBasedJSObjectArray": {
+      let a = [];
+      for (let i = 0; i < 8; i++) {
+        a[i] = o;
+      }
+      Object.seal(a);
+      assertArrayType(a, jsobjectArrayType);
+
+      a[5] = x;
+
+      assertArrayType(a, objectArrayType);
+      assertSameContent([o,o,o,o,o,x,o,o], a);
+      assertTrue(Object.isSealed(a));
+      break;
+    }
+    case "ContiguousJSObjectArray": {
+      let a = [];
+      for (let i = 1; i < 8; i++) {
+        a[i] = o;
+      }
+      Object.seal(a);
+      assertArrayType(a, jsobjectArrayType);
+
+      a[0] = x;
+      assertArrayType(a, jsobjectArrayType);
+
+      a[5] = x;
+      assertArrayType(a, objectArrayType);
+      assertSameContent([ ,o,o,o,o,x,o,o], a);
+      assertTrue(Object.isSealed(a));
+      break;
+    }
+    case "HolesJSObjectArray": {
+      let a = [];
+      for (let i = 0; i < 8; i++) {
+        if (i == 4) {
+          continue;
+        }
+        a[i] = o;
+      }
+      Object.seal(a);
+      assertArrayType(a, jsobjectArrayType);
+
+      a[4] = x;
+      assertArrayType(a, jsobjectArrayType);
+      a[5] = x;
+
+      assertArrayType(a, objectArrayType);
+      assertSameContent([o,o,o,o, ,x,o,o], a);
+      assertTrue(Object.isSealed(a));
+      break;
+    }
+    default: throw new TypeError(jsobjectArrayType);
+  }
+}
+
+function assertArrayType(array, expected) {
+  assertSame(expected, Debug.arraytype(array))
+}