Firebase 未处理的错误 RangeError : Maximum call stack size exceeded

Question

我正在调用 Firebase 可调用函数，并返回 Firebase 指定的 promise ，但收到此错误:

未处理的错误 RangeError:超出最大调用堆栈大小

代码如下:

exports.getProductInfo = functions.https.onCall((data, context) => {
  // Message text passed from the client.
  const product = data.product;
  // Authentication / user information is automatically added to the request.
  // const uid = context.auth.uid;

  // Get the current Server Timestamp
  var ts = String(Date.now());
  var key, snap, node;

  // Get the price of the specified product
  return database.ref('/products/' + product)
                 .orderByKey()
                 .endAt(ts)
                 .limitToLast(1)
                 .once('value', function (snapshot) {
                   snap = snapshot.val();
                   console.log('snap: ' + JSON.stringify(snap));

                   key = Object.keys(snap)[0];
                   node = snap[key];
                   console.log('node: ' + JSON.stringify(node));

                   return(node);
                 });
});

这是我在函数日志中看到的输出:

snap: {"1538004276":{"description":"这是基本产品","price":40}}

节点:{“description”:“这是基本产品”，“price”:40}

Unhandled error RangeError: Maximum call stack size exceeded
    at Object (native)
    at /user_code/node_modules/firebase-functions/node_modules/lodash/lodash.js:4905:24
    at baseForOwn (/user_code/node_modules/firebase-functions/node_modules/lodash/lodash.js:2996:24)
    at Function.mapValues (/user_code/node_modules/firebase-functions/node_modules/lodash/lodash.js:13401:7)
    at encode (/user_code/node_modules/firebase-functions/lib/providers/https.js:242:18)
    at /user_code/node_modules/firebase-functions/node_modules/lodash/lodash.js:13402:38
    at /user_code/node_modules/firebase-functions/node_modules/lodash/lodash.js:4911:15
    at baseForOwn (/user_code/node_modules/firebase-functions/node_modules/lodash/lodash.js:2996:24)
    at Function.mapValues (/user_code/node_modules/firebase-functions/node_modules/lodash/lodash.js:13401:7)
    at encode (/user_code/node_modules/firebase-functions/lib/providers/https.js:242:18)
    at /user_code/node_modules/firebase-functions/node_modules/lodash/lodash.js:13402:38
    at /user_code/node_modules/firebase-functions/node_modules/lodash/lodash.js:4911:15
    at baseForOwn (/user_code/node_modules/firebase-functions/node_modules/lodash/lodash.js:2996:24)
    at Function.mapValues (/user_code/node_modules/firebase-functions/node_modules/lodash/lodash.js:13401:7)
    at encode (/user_code/node_modules/firebase-functions/lib/providers/https.js:242:18)
    at /user_code/node_modules/firebase-functions/node_modules/lodash/lodash.js:13402:38
    at /user_code/node_modules/firebase-functions/node_modules/lodash/lodash.js:4911:15
    at baseForOwn (/user_code/node_modules/firebase-functions/node_modules/lodash/lodash.js:2996:24)
    at Function.mapValues (/user_code/node_modules/firebase-functions/node_modules/lodash/lodash.js:13401:7)
    at encode (/user_code/node_modules/firebase-functions/lib/providers/https.js:242:18)
    at /user_code/node_modules/firebase-functions/node_modules/lodash/lodash.js:13402:38
    at /user_code/node_modules/firebase-functions/node_modules/lodash/lodash.js:4911:15
    at baseForOwn (/user_code/node_modules/firebase-functions/node_modules/lodash/lodash.js:2996:24)
    at Function.mapValues (/user_code/node_modules/firebase-functions/node_modules/lodash/lodash.js:13401:7)

救命!

Answer 1

问题类似于the one described here 。您将返回一个由 Firebase API 生成的复杂对象，称为 DocumentSnapshot。快照本身并不是返回给客户端的原始 JSON 数据，它包含对其他对象的循环引用。 Cloud Functions 在尝试序列化所有这些对象时陷入困境。相反，只需通过在快照上调用 val() 返回感兴趣位置处的数据的原始 JavaScript 对象即可:

return database
    .ref('/products/' + product)
    .orderByKey()
    .endAt(ts)
    .limitToLast(1)
    .once('value')             // once() returns a promise containing a snapshost
    .then(snapshot => {
        return snapshot.val()  // this is the raw JS object
    })

您通常不会在同一调用中同时使用返回的 promise 和回调。仅使用 Promise 会更容易。