Bug 1049041 - Remove scary warning about mutating [[Prototype]]. r=efaust.

--HG--
extra : commitid : JkYGz4dusnf
extra : rebase_source : e23ad9b51c9b5f0049edd96ca3cb1fea879b3289

js/src/builtin/Object.cpp

@@ -383,10 +383,6 @@ obj_setPrototypeOf(JSContext* cx, unsigned argc, Value* vp)
 {
     CallArgs args = CallArgsFromVp(argc, vp);
 
-    RootedObject setPrototypeOf(cx, &args.callee());
-    if (!GlobalObject::warnOnceAboutPrototypeMutation(cx, setPrototypeOf))
-        return false;
-
     if (args.length() < 2) {
         JS_ReportErrorNumber(cx, GetErrorMessage, nullptr, JSMSG_MORE_ARGS_NEEDED,
                              "Object.setPrototypeOf", "1", "");
@@ -1054,13 +1050,6 @@ ProtoSetter(JSContext* cx, unsigned argc, Value* vp)
 {
     CallArgs args = CallArgsFromVp(argc, vp);
 
-    // Do this here, rather than after the this-check so even likely-buggy
-    // use of the __proto__ setter on unacceptable values, where no subsequent
-    // use occurs on an acceptable value, will trigger a warning.
-    RootedObject callee(cx, &args.callee());
-    if (!GlobalObject::warnOnceAboutPrototypeMutation(cx, callee))
-       return false;
-
     HandleValue thisv = args.thisv();
     if (thisv.isNullOrUndefined()) {
         ReportIncompatible(cx, args);

js/src/js.msg

@@ -76,7 +76,6 @@ MSG_DEF(JSMSG_BAD_SURROGATE_CHAR,      1, JSEXN_TYPEERR, "bad surrogate characte
 MSG_DEF(JSMSG_UTF8_CHAR_TOO_LARGE,     1, JSEXN_TYPEERR, "UTF-8 character {0} too large")
 MSG_DEF(JSMSG_MALFORMED_UTF8_CHAR,     1, JSEXN_TYPEERR, "malformed UTF-8 character sequence at offset {0}")
 MSG_DEF(JSMSG_BUILTIN_CTOR_NO_NEW,     1, JSEXN_TYPEERR, "calling a builtin {0} constructor without new is forbidden")
-MSG_DEF(JSMSG_PROTO_SETTING_SLOW,      0, JSEXN_NONE, "mutating the [[Prototype]] of an object will cause your code to run very slowly; instead create the object with the correct initial [[Prototype]] value using Object.create")
 MSG_DEF(JSMSG_BAD_GENERATOR_YIELD,     1, JSEXN_TYPEERR, "yield from closing generator {0}")
 MSG_DEF(JSMSG_EMPTY_ARRAY_REDUCE,      0, JSEXN_TYPEERR, "reduce of empty array with no initial value")
 MSG_DEF(JSMSG_UNEXPECTED_TYPE,         2, JSEXN_TYPEERR, "{0} is {1}")

js/src/tests/shell/warning.js

@@ -9,14 +9,15 @@ print(BUGNUMBER + ": " + summary);
 
 enableLastWarning();
 
-eval(`({}).__proto__ = {};`);
+let line0 = new Error().lineNumber;
+assertEq("foo".contains("bar"), false);
 
 var warning = getLastWarning();
 assertEq(warning !== null, true);
 assertEq(warning.name, "None");
-assertEq(warning.message.includes("mutating"), true);
-assertEq(warning.lineNumber, 1);
-assertEq(warning.columnNumber, 2);
+assertEq(warning.message.includes("deprecated"), true);
+assertEq(warning.lineNumber, line0 + 1);
+assertEq(warning.columnNumber, 10);
 
 // Clear last warning.
 

js/src/vm/GlobalObject.h

@@ -135,8 +135,7 @@ class GlobalObject : public NativeObject
 
     enum WarnOnceFlag : int32_t {
         WARN_WATCH_DEPRECATED                   = 1 << 0,
-        WARN_PROTO_SETTING_SLOW                 = 1 << 1,
-        WARN_STRING_CONTAINS_DEPRECATED         = 1 << 2,
+        WARN_STRING_CONTAINS_DEPRECATED         = 1 << 1,
     };
 
     // Emit the specified warning if the given slot in |obj|'s global isn't
@@ -699,12 +698,6 @@ class GlobalObject : public NativeObject
         return true;
     }
 
-    // Warn about use of the given __proto__ setter to attempt to mutate an
-    // object's [[Prototype]], if no prior warning was given.
-    static bool warnOnceAboutPrototypeMutation(JSContext* cx, HandleObject protoSetter) {
-        return warnOnceAbout(cx, protoSetter, WARN_PROTO_SETTING_SLOW, JSMSG_PROTO_SETTING_SLOW);
-    }
-
     // Warn about use of the deprecated String.prototype.contains method
     static bool warnOnceAboutStringContains(JSContext* cx, HandleObject strContains) {
         return warnOnceAbout(cx, strContains, WARN_STRING_CONTAINS_DEPRECATED,

js/src/vm/Xdr.h

@@ -31,11 +31,11 @@ namespace js {
  *
  * (If you're wondering, 0xb973c0de is used because it looks like "bytecode".)
  */
-static const uint32_t XDR_BYTECODE_VERSION_SUBTRAHEND = 353;
+static const uint32_t XDR_BYTECODE_VERSION_SUBTRAHEND = 354;
 static const uint32_t XDR_BYTECODE_VERSION =
     uint32_t(0xb973c0de - XDR_BYTECODE_VERSION_SUBTRAHEND);
 
-static_assert(JSErr_Limit == 420,
+static_assert(JSErr_Limit == 419,
               "GREETINGS, POTENTIAL SUBTRAHEND INCREMENTER! If you added or "
               "removed MSG_DEFs from js.msg, you should increment "
               "XDR_BYTECODE_VERSION_SUBTRAHEND and update this assertion's "

js/xpconnect/tests/mochitest/test_bug1021258.html

@@ -1,52 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<!--
-https://bugzilla.mozilla.org/show_bug.cgi?id=1021258
--->
-<head>
-  <meta charset="utf-8">
-  <title>Test for Bug 1021258</title>
-  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
-  <script type="application/javascript">
-
-  /** Test for proto mutation warnings. **/
-
-  SimpleTest.waitForExplicitFinish();
-  var gLoads = 0;
-  function loaded() {
-    switch (++gLoads) {
-      case 1:
-        info("First load");
-        SimpleTest.monitorConsole(function() { window[0].location.reload(true); },
-                                  [ { message: /mutating/ } ], /* forbidUnexpectedMessages = */ true);
-        window[0].eval('var foo = {}; Object.setPrototypeOf(foo, {});' +
-                       'var bar = {}; Object.getPrototypeOf(bar, {});');
-        SimpleTest.endMonitorConsole();
-        break;
-      case 2:
-        info("Second load");
-        SimpleTest.monitorConsole(SimpleTest.finish.bind(SimpleTest),
-                                  [ { message: /mutating/ } ], /* forbidUnexpectedMessages = */ true);
-        window[0].eval('var foo = {}; foo.__proto__ = {};' +
-                       'var bar = {}; bar.__proto__ = {};');
-        SimpleTest.endMonitorConsole();
-        break;
-      case 3:
-        ok(false, "Shouldn't have 3 loads!");
-    }
-  }
-
-  </script>
-</head>
-<body>
-<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1021258">Mozilla Bug 1021258</a>
-<p id="display"></p>
-<div id="content" style="display: none">
-
-</div>
-<pre id="test">
-</pre>
-<iframe id="ifr" src="file_empty.html" onload="loaded();"></iframe>
-</body>
-</html>