Revert of Make Error.prototype.toString spec compliant; and fix various side-effect-free error printing metho…

test/mjsunit/error-constructors.js

Index: test/mjsunit/error-constructors.js
diff --git a/test/mjsunit/error-constructors.js b/test/mjsunit/error-constructors.js
index 5c2aac5b8703cb421a69066465d437c6aae9254f..0f3d74c960cfb04ad84be7919e5dca9eeab8338e 100644
--- a/test/mjsunit/error-constructors.js
+++ b/test/mjsunit/error-constructors.js
@@ -69,11 +69,9 @@
 assertTrue(e.hasOwnProperty('stack'));
 
 // Check that intercepting property access from toString is prevented for
-// compiler errors. This is not specified, but allowing interception through a
-// getter can leak error objects from different script tags in the same context
-// in a browser setting. Use Realm.eval as a proxy for loading scripts. We
-// ignore the exception thrown from it since that would not be catchable from
-// user-land code.
+// compiler errors. This is not specified, but allowing interception
+// through a getter can leak error objects from different
+// script tags in the same context in a browser setting.
 var errors = [SyntaxError, ReferenceError, TypeError, RangeError, URIError];
 var error_triggers = ["syntax error",
                       "var error = reference",
@@ -81,12 +79,39 @@
                       "String.fromCodePoint(0xFFFFFF)",
                       "decodeURI('%F')"];
 for (var i in errors) {
+  var name = errors[i].name;
+
   // Monkey-patch prototype.
-  for (var prop of ["name", "message", "stack"]) {
-    errors[i].prototype.__defineGetter__(prop, fail);
+  var props = ["name", "message", "stack"];
+  for (var j in props) {
+    errors[i].prototype.__defineGetter__(props[j], fail);
   }
   // String conversion should not invoke monkey-patched getters on prototype.
-  assertThrows(()=>Realm.eval(0, error_triggers[i]));
+  var error;
+  try {
+    eval(error_triggers[i]);
+  } catch (e) {
+    error = e;
+  }
+  assertTrue(error.toString().startsWith(name));
+
+  // Deleting message on the error (exposing the getter) is fine.
+  delete error.message;
+  assertEquals(name, error.toString());
+
+  // Custom properties shadowing the name are fine.
+  var myerror = { name: "myerror", message: "mymessage"};
+  myerror.__proto__ = error;
+  assertEquals("myerror: mymessage", myerror.toString());
+
+  // Custom getters in actual objects are welcome.
+  error.__defineGetter__("name", function() { return "mine"; });
+  assertEquals("mine", error.toString());
+
+  // Custom properties shadowing the name are fine.
+  var myerror2 = { message: "mymessage"};
+  myerror2.__proto__ = error;
+  assertEquals("mine: mymessage", myerror2.toString());
 }
 
 // Monkey-patching non-internal errors should still be observable.