Firestore 云功能 - 如何返回第二个查询

Question

我有一个 on-create 云功能，我想将数据从一个容器移动到另一个容器。第一个查询似乎运行正常（我正在检查数据），但我添加的第二个查询似乎失败了，我知道我必须从云函数返回一个承诺，但它仍然应该返回内部的？

exports.msgMove = functions.firestore.document('/msgTemp/{documentId}')
.onCreate( (snap:any, context:any) => {

  const data = snap.data();

  // Has this user already replied?
  return firestore.collection("msg")
  .where('threadId', '==', snap.data().threadId)
  .where('trackId', '==', snap.data().trackId)
  .where('uid', '==',  snap.data().uid)
  .orderBy("created", "desc")
  .limit(1)
  .get()
  .then(async (query) => {

      if(query.empty){

        const {threadId, trackId, uid} = snap.data();

        // Below seems to be failing
        const add = await firestore.collection("msg").add(
          {
            threadId,
            trackId,
            uid
          }
        );

        return add;

      }

      return;

  })
});

我得到了错误：

{"severity":"WARNING","message":"函数返回未定义，预期的 Promise 或值"}

Answer 1

不推荐您将then() 和async/await (.then(async (query) => {...})) 混合使用。

你应该这样做：

仅使用then()

exports.msgMove = functions.firestore.document('/msgTemp/{documentId}')
    .onCreate((snap: any, context: any) => {

        const data = snap.data();

        // Has this user already replied?
        return firestore.collection("msg")
            .where('threadId', '==', data.threadId)
            .where('trackId', '==', data.trackId)
            .where('uid', '==', data.uid)
            .orderBy("created", "desc")
            .limit(1)
            .get()
            .then((querySnapshot) => {
                if (querySnapshot.empty) {
                    const { threadId, trackId, uid } = snap.data();

                    return firestore.collection("msg").add(
                        {
                            threadId,
                            trackId,
                            uid
                        }
                    );
                } else {
                    return null;
                }

            });
    });

我们使用 then()（它返回一个 Promise）由 Firebase 异步方法返回的 chain the promises。

仅使用async/await

exports.msgMove = functions.firestore
    .document('/msgTemp/{documentId}')
    .onCreate(async (snap: any, context: any) => {   // <== See the async keyword
   
        const data = snap.data();

        // Has this user already replied?
        const querySnapshot = await firestore
            .collection('msg')
            .where('threadId', '==', data.threadId)
            .where('trackId', '==', data.trackId)
            .where('uid', '==', data.uid)
            .orderBy('created', 'desc')
            .limit(1)
            .get();

        if (querySnapshot.empty) {
            const { threadId, trackId, uid } = snap.data();

            await firestore.collection('msg').add({
                threadId,
                trackId,
                uid,
            });
        }
        return null;
    });