为什么在 Node 7.2.0 中记录被拒绝的“Promise”会导致同时记录堆栈跟踪？

Question

在 Node 7.2.0 中运行此代码时：

let prms = Promise.reject(new Error('error'));
prms.catch(() => {});

console.log(prms);

我期待 Promise {<rejected> Error: error} 被记录到控制台，但我收到了以下输出：

Promise {
  <rejected> Error: error
    at Object.<anonymous> (/Users/davidlund/Dropbox/test.js:1:89)
    at Module._compile (module.js:571:32)
    at Object.Module._extensions..js (module.js:580:10)
    at Module.load (module.js:488:32)
    at tryModuleLoad (module.js:447:12)
    at Function.Module._load (module.js:439:3)
    at Module.runMain (module.js:605:10)
    at run (bootstrap_node.js:420:7)
    at startup (bootstrap_node.js:139:9)
    at bootstrap_node.js:535:3 }

为什么会这样？

Answer 1

您看到的是错误的.valueOf 表示：

> (new Error('error')).valueOf();
Error: error
    at repl:1:2
    at realRunInThisContextScript (vm.js:22:35)
    at sigintHandlersWrap (vm.js:98:12)
    at ContextifyScript.Script.runInThisContext (vm.js:24:12)
    at REPLServer.defaultEval (repl.js:313:29)
    at bound (domain.js:280:14)
    at REPLServer.runBound [as eval] (domain.js:293:12)
    at REPLServer.onLine (repl.js:513:10)
    at emitOne (events.js:101:20)
    at REPLServer.emit (events.js:188:7)

比较：

function Foo() {

}

Foo.prototype.valueOf = function () {
    return "FOOBAR"
}

let prms = Promise.reject(new Foo);
prms.catch(() => {});

console.log(prms); // Promise { <rejected> [String: 'FOOBAR'] }