从Flatter调用Firebase可调用函数时无法处理错误

Question

我正在从Flatter调用Firebase可调用函数，尽管我已经尝试了几乎所有的方法，但仍然无法处理可调用函数抛出的错误。

我的可调用函数如下所示：

js prettyprint-override">import * as functions from "firebase-functions";

const admin = require('firebase-admin');
admin.initializeApp();
const db = admin.firestore();

export const myFunction = functions.https.onCall((data, context) => {

    //Get data passed to the function
    const someData = data.someData;
    
    //Run transaction
    return db.runTransaction(async (transaction: any) => {
        //Get data
        const docRef = db.collection("myCollection").doc("myDocId");
        const docResults = await transaction.get(docRef);
        const docData = docResults.data();

        //Run validations:
        if(1 != 0){
            throw new functions.https.HttpsError('failed-precondition', "Error on purpose");
        }
        
        //Create a new doc
        const newDocRef = db.collection('myCollection').doc();
        transaction.set(newDocRef, {someData: "myData",});

        return {newDocId: newDocRef.id}
    });

  });

然后，我在flatter中创建了一个Future来调用我的可调用函数：

import 'package:cloud_functions/cloud_functions.dart';

Future<String> callMyFunction({String someData,}) async {
  HttpsCallable callable = FirebaseFunctions.instance.httpsCallable(
      'myFunction',  options: HttpsCallableOptions(timeout: Duration(seconds: 5)));

  try {
    return callable.call({
      'someData': someData,
    }).then((results) {
      return results.data['newDocId'].toString();
    }).catchError(handleError); //First error handler
  } catch (error) {
    //Second error handler
    print("Missed the first error handler.");
    handleError(error);
    return null;
  }
}

void handleError(error) {
  print("Got this error:");
  print(error);
}

最后，我用另一个错误处理程序从一个文本按钮调用我的未来：

import 'package:flutter/material.dart';
import 'package:myApp/callableFuture.dart';

class myWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return TextButton(
      child: Text("Press me"),
      onPressed: () {
        callMyFunction(
          someData: "Hi",
        ).catchError((error) {
          //This is my third error handler
          print("Missed first two error handlers. Got this error:");
          print(error);
        }).then((newDocId) =>
            print("Got this doc id: $newDocId"));
      },
    );
  }
}

当我调用我的函数并得到一个错误时，我的代码立即跳转到-并停止在-Flutter的method_channel_https_callable.dart（位于.../flutter/. pub-cache/托管/pub.dartlang.org/cloud_functions_platfrom_interface-5..0.15/lib/src/method_channel/method_channel_https_callable.dart）。

它停在函数call处的类Method odChannelHttpsCallable，就在这里：

try {
      //...some code...

      if (result is Map) {
        return Map<String, dynamic>.from(result);
      } else {
        return result;
      }
    } catch (e, s) {
      throw convertPlatformException(e, s); //My code stops right here.
    }

最后，在VSCode中单击单步执行后，控制台会显示以下内容：

出现以下错误：

[firebase\u函数/失败的前提条件]故意出错。

#0 StandardMethodCodec。decodeEnvelope包：flatter/../services/message\u编解码器。dart:597

_invokeMethod包：flutter/.../service/platform_channel.dart:158

#2方法通道HttpScalable。调用包：cloud\u functions\u platform\u interface/../method\u channel/method\u channel\u https\u callable。省道：23

#3 HttpsCallable.call包：cloud_functions/src/https_callable.dart:35

Answer 1

我真的不知道为什么，但这解决了问题：

我改变了调用可调用函数的未来：

import 'package:cloud_functions/cloud_functions.dart';

Future<String> callMyFunction({String someData,}) async {
  HttpsCallable callable = FirebaseFunctions.instance.httpsCallable(
      'myFunction',  options: HttpsCallableOptions(timeout: Duration(seconds: 5)));

  try {
    return callable.call({
      'someData': someData,
    }).then((results) {
      return results.data['newDocId'].toString();
    }).catchError(handleError); //First error handler
  } catch (error) {
    //Second error handler
    print("Missed the first error handler.");
    handleError(error);
    return null;
  }
}

void handleError(error) {
  print("Got this error:");
  print(error);
}

为此：

import 'package:cloud_functions/cloud_functions.dart';

Future<String> callMyFunction({String someData,}) async {
  HttpsCallable callable = FirebaseFunctions.instance.httpsCallable(
      'myFunction',  options: HttpsCallableOptions(timeout: Duration(seconds: 5)));

  HttpsCallableResult results;

  try {
    results = await callable.call({
      'someData': someData,
    });
  } catch (error) {
    print("Got this error:");
    print(error.code);
    print(error.message);
    return null;
  }

  return results.data['newDocId'].toString();
}

Answer 2

通过查看您的输出日志和代码，很明显您的第一个错误处理程序正在根据以下行为您解析或处理错误：

I/flutter (21112): Got this error: I/flutter (21112): [firebase_functions/failed-precondition] Error on purpose.

由于来自Firebase函数的错误由第一个错误处理程序处理（或“解决”），因此其他两个错误处理程序没有理由运行，因为它们没有收到任何错误。这使得从您的按钮执行的Future要被解析，尽管具有null值。

在这种情况下，您可以做的是按照Dart中建议的那样，在您的第一个错误处理程序中重新抛出错误，因此它可以在第二个处理程序中处理，并再次将其重新抛出到第三个处理程序。我相信在这种情况下，第二个处理程序是多余的，您可以将错误从第一个处理程序重新抛出到第三个处理程序。catchError（）子句已经在Dart中用作try/catch块。

Firebase函数

exports.myFuncEmu = functions.https.onCall((data,context) => {
  const testData = data.text;

  if(testData == "throwEx"){
    throw new functions.https.HttpsError('failed-precondition', "Error on purpose");
  }

  console.log(testData);
  return `Finished: ${testData}`
});

扑腾未来

Future<String?> runFunction(String text) async {
  await Firebase.initializeApp();
  FirebaseFunctions.instance.useFunctionsEmulator('localhost', 5001);
  HttpsCallable callableFunc =
      FirebaseFunctions.instance.httpsCallable("myFuncEmu");

  try {
    return await callableFunc.call(
      {"text": text},
    ).then((res) {
      return res.data.toString();
    }).catchError(handleError); //Handler from callable function
  } catch (err) {
    print("Missed the first error handler"); //Try/catch block handler
    rethrow; //Throws here so it can be caught by Future handler in button widget
    return null;
  }
}

String handleError(err) {
  print("Caught error: ");
  print(err);
  throw Exception(err); //Throws here so it can be caught by try/catch handler
  return "";
}

颤振按钮

child: ElevatedButton( //Swapped order of then and catcherror clauses
                onPressed: () {
                  runFunction("throwEx")
                      .then((val) => print("Final result: ${val}"))
                      .catchError((err) {
                    print(
                        "Missed first two error handlers"); //Handler from Future function
                    print(err);
                  });
                },
                child: const Text(
                  "RUN",
                  style: TextStyle(color: Colors.white),
                ),
              ),

通过添加所需的throw/rethrow语句，我们可以通过错误处理程序正确重定向此错误，以便在发现错误后阻止代码执行：

Caught error:
[firebase_functions/failed-precondition] Error on purpose
Missed the first error handler
Missed first two error handlers
Exception: [firebase_functions/failed-precondition] Error on purpose

省略rethrow/throw语句：

Caught error:
[firebase_functions/failed-precondition] Error on purpose
Final result: //Incorrectly continues code, seems to not be handling errors