Everywhere: Hoist the Libraries folder to the top-level

Author: https://github.com/trflynn89
Commit: https://github.com/LadybirdBrowser/ladybird/commit/93712b24bf2
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2256
Reviewed-by: https://github.com/sideshowbarker

Libraries/LibJS/Tests/builtins/Proxy/Proxy.handler-preventExtensions.js

@@ -0,0 +1,59 @@
+describe("[[PreventExtension]] trap normal behavior", () => {
+    test("forwarding when not defined in handler", () => {
+        let p = new Proxy({}, { preventExtensions: null });
+        expect(Object.preventExtensions(p)).toBe(p);
+        p = new Proxy({}, { preventExtensions: undefined });
+        expect(Object.preventExtensions(p)).toBe(p);
+        p = new Proxy({}, {});
+        expect(Object.preventExtensions(p)).toBe(p);
+    });
+
+    test("correct arguments supplied to trap", () => {
+        let o = {};
+        p = new Proxy(o, {
+            preventExtensions(target) {
+                expect(target).toBe(o);
+                return true;
+            },
+        });
+
+        Object.preventExtensions(o);
+        Object.preventExtensions(p);
+    });
+});
+
+describe("[[PreventExtensions]] invariants", () => {
+    test("cannot return false", () => {
+        let p = new Proxy(
+            {},
+            {
+                preventExtensions() {
+                    return false;
+                },
+            }
+        );
+
+        expect(() => {
+            Object.preventExtensions(p);
+        }).toThrowWithMessage(TypeError, "Object's [[PreventExtensions]] method returned false");
+    });
+
+    test("cannot return true if the target is extensible", () => {
+        let o = {};
+        let p = new Proxy(o, {
+            preventExtensions() {
+                return true;
+            },
+        });
+
+        expect(() => {
+            Object.preventExtensions(p);
+        }).toThrowWithMessage(
+            TypeError,
+            "Proxy handler's preventExtensions trap violates invariant: cannot return true if the target object is extensible"
+        );
+
+        Object.preventExtensions(o);
+        expect(Object.preventExtensions(p)).toBe(p);
+    });
+});