Bug 978235 - Reland forgotten test. r=me

js/src/tests/ecma_6/Proxy/proxy-isExtensible.js

@@ -0,0 +1,94 @@
+// Test ES6 Proxy trap compliance for Object.isExtensible() on exotic proxy
+// objects.
+var unsealed = {};
+var sealed = Object.seal({});
+var handler = {};
+
+assertEq(Object.isExtensible(unsealed), true);
+assertEq(Object.isExtensible(sealed), false);
+
+var targetSealed = new Proxy(sealed, handler);
+var targetUnsealed = new Proxy(unsealed, handler);
+
+var handlerCalled = false;
+
+// without traps, forward to the target
+// First, make sure we get the obvious answer on a non-exotic target.
+assertEq(Object.isExtensible(targetSealed), false, "Must forward to target without hook.");
+assertEq(Object.isExtensible(targetUnsealed), true, "Must forward to target without hook.");
+
+// Now, keep everyone honest. What if the target itself is a proxy?
+function ensureCalled() { handlerCalled = true; return true; }
+var proxyTarget = new Proxy({}, { isExtensible : ensureCalled });
+assertEq(Object.isExtensible(new Proxy(proxyTarget, {})), true, "Must forward to target without hook.");
+assertEq(handlerCalled, true, "Must forward to target without hook.");
+
+// with traps, makes sure that the handler is called, and that we throw if the
+// trap disagrees with the target
+function testExtensible(obj, shouldThrow, expectedResult)
+{
+    handlerCalled = false;
+    if (shouldThrow)
+        assertThrowsInstanceOf(function () { Object.isExtensible(obj); },
+                               TypeError, "Must throw if handler and target disagree.");
+    else
+        assertEq(Object.isExtensible(obj), expectedResult, "Must return the correct value.");
+    assertEq(handlerCalled, true, "Must call handler trap if present");
+}
+
+// What if the trap says it's necessarily sealed?
+function fakeSealed() { handlerCalled = true; return false; }
+handler.isExtensible = fakeSealed;
+testExtensible(targetSealed, false, false);
+testExtensible(targetUnsealed, true);
+
+// What if the trap says it's never sealed?
+function fakeUnsealed() { handlerCalled = true; return true; }
+handler.isExtensible = fakeUnsealed;
+testExtensible(targetSealed, true);
+testExtensible(targetUnsealed, false, true);
+
+// make sure we are able to prevent further extensions mid-flight and throw if the
+// hook tries to lie.
+function makeSealedTruth(target) { handlerCalled = true; Object.preventExtensions(target); return false; }
+function makeSealedLie(target) { handlerCalled = true; Object.preventExtensions(target); return true; }
+handler.isExtensible = makeSealedTruth;
+testExtensible(new Proxy({}, handler), false, false);
+handler.isExtensible = makeSealedLie;
+testExtensible(new Proxy({}, handler), true);
+
+// What if the trap doesn't directly return a boolean?
+function falseyNonBool() { handlerCalled = true; return undefined; }
+handler.isExtensible = falseyNonBool;
+testExtensible(targetSealed, false, false);
+testExtensible(targetUnsealed, true);
+
+function truthyNonBool() { handlerCalled = true; return {}; }
+handler.isExtensible = truthyNonBool;
+testExtensible(targetSealed, true);
+testExtensible(targetUnsealed, false, true);
+
+// What if the trap throws?
+function ExtensibleError() { }
+ExtensibleError.prototype = new Error();
+ExtensibleError.prototype.constructor = ExtensibleError;
+function throwFromTrap() { throw new ExtensibleError(); }
+handler.isExtensible = throwFromTrap;
+
+// exercise some other code paths and make sure that they invoke the trap and
+// can handle the ensuing error.
+assertThrowsInstanceOf(function () { Object.isExtensible(targetSealed); },
+                       ExtensibleError, "Must throw if the trap does.");
+assertThrowsInstanceOf(function () { Object.isFrozen(targetSealed); },
+                       ExtensibleError, "Must throw if the trap does.");
+assertThrowsInstanceOf(function () { Object.isSealed(targetSealed); },
+                       ExtensibleError, "Must throw if the trap does.");
+
+
+// What if the trap likes to re-ask old questions?
+function recurse() { return Object.isExtensible(targetSealed); }
+handler.isExtensible = recurse;
+assertThrowsInstanceOf(function () { Object.isExtensible(targetSealed); },
+                       InternalError, "Should allow and detect infinite recurison.");
+
+reportCompare(0, 0, "OK");