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Custom error message in Google Apps Script Error object [duplicate]

This is a doPost function inside a Google App that returns a Hello World message.
function doPost(e){
return ContentService.createTextOutput('Hello World');
}
Now suppose I want to only accept valid JSON to be posted to this Google App endpoint and I want to send a respones with Bad Request status. How can I do that. Here's the pseudo code:
function doPost(e){
try{
const data = JSON.parse(e.postData.contents);
return ContentService.createTextOutput('Hello World');
}catch(err){
// Send Bad Request
}
}

Issue and workaround:
Unfortunately, in the current stage, ContentService cannot modify the status code. When I saw the official document of Class ContentService, such method cannot be found. Ref It seems that this is the current specification.
So in your situation, as the current workaround, how about returning the value as JSON data? By this, you can check the value using the key of JSON data. For example, how about the following sample script?
When the correct value without the error is returned,
return ContentService.createTextOutput(JSON.stringify({value: 'value'}));
When the value with the error is returned,
return ContentService.createTextOutput(JSON.stringify({error: 'Error message'}));
When you need .setMimeType(ContentService.MimeType.JSON), please add this.
Note:
When I searched about this at the Google issue tracker, I couldn't find it. So how about reporting this as the future request? Ref
Reference:
Class ContentService

Here's another workaround that allows raising errors on the client side for errors on the web app side. For example, a client might need to catch errors such as bad url args sent to the web app (i.e. the OP's question), or catch errors thrown by a method that is called from doGet() or doPost().
As far as I know, when an error is thrown downstream of doGet() or doPost(), a text error message is returned in the response, but the web app request itself succeeds, so there is no error thrown on the client side. As #Tanaike said, there still seems no way for a Google web app dev to throw an HTTP error from the app (like 400 Bad Request or 500 Internal Server Error).
The idea involves returning a function body from the web app, which the client can use to create and run a dynamic function via the Function() constructor (this assumes Javascript is available on the client).
So the web app can be written to:
return a function body that will throw an error for bad args, server method errors, etc.
return a function body that will return intended JSON when there is no error
This is a bit of a hack, but it unifies error handling on the client side. The client makes the http request, constructs a function using the function body returned in the response, and then runs this function, all in one try{} block. Then both Google-raised http errors and web app downstream errors can be caught in the catch{} block.
Example setup for a Google Apps Script client making a request to a Google web app:
(1) In the web app doGet() or doPost() function:
// this string will be returned by the webapp
var fnBody;
// for bad url args, return a fnBody that will throw an error with an indicative message
if(!urlArgsOk()) {
fnBody = "'use strict'; throw new Error('POST args error');";
}
// if url args are ok, call server method
else {
try {
// if the method call succeeds, return a fnBody that will return the intended JSON
var returnObj = myServerMethod(methodArgs);
fnBody = "'use strict'; return JSON.stringify(" + JSON.stringify(returnObj) + ");";
}
catch(serverErr) {
// if the method call fails, return a fnBody that will throw an error ...
// ... simple example shown here, but info from serverErr can be included in fnBody
fnBody = "'use strict'; throw new Error('server error');";
}
}
// return fnBody, which can be run via Function() on the client
return ContentService.createTextOutput(fnBody).setMimeType(ContentService.MimeType.TEXT);
(2) On the client side (Google apps script client making a POST request)
// Set the url, payload, and fetch options
var url = "https://script.google.com/_______/exec?arg1=val1&arg2=val2";
var payload = getPayloadString(); // whatever POST payload needs to be sent
var options = {
'method' : 'POST',
'contentType': 'application/json',
'muteHttpExceptions': false, // let Google http exceptions come through
'payload' : payload,
'headers': {authorization: "Bearer " + ScriptApp.getOAuthToken()}
};
// Send a request to the web app
try {
// make the POST request - this throws Google-generated HTTP errors if any
var response = UrlFetchApp.fetch(url, options);
// create the dynamic function from the fnBody returned
var responseFn = new Function(response.getContentText());
// run the function - this returns intended JSON content
// or throws web app downstream errors if any
var responseJson = responseFn();
}
catch(err) {
// handle either source of error
console.log(err.message);
}
There are potential security risks associated with dynamic code, so I'm not sure how widely applicable this might be. I might use this in an aplication that lives entirely in a private GCP domain, i.e. with the web app restricted to same-domain users and the client app also in the same domain. Some security is also added by the 'use strict' directive, which boxes the dynamic function in by setting its this to undefined (ref). But it's still a good idea to think through the dynamic code implications (ref1, ref2).

How to handle Bad JSON in Firebase Cloud Functions?

I'm creating a firebase application which uses firebase-cloud-functions.
index.js
exports.auth = functions.https.onRequest((request, response) => {
response.status(200).send({
status : "Some Status"
});
}
This is very simple functions. I want to make a POST request on the endpoint with some payload. When I tested the API using Firebase Cloud Function Emulator and POSTman with bad json
{
"phoneNumber: "9632725300"
}
The server just crashed! My question is how to handle the bad request in firebase functions like these.
with this error

The server did not crash. You have sent it a bad request (malformed JSON) and it responded perfectly with a status code 400 which is "Bad Request".
You'd rather correct your JSON...
EDIT:
If you really wanted to be able to send invalid JSON, you could do so by circumventing the JSON body parser. To do so, you could either change your request to have a content-type header set to "text/plain". This content-type will use the text body parser, which will not parse any JSON.
Note that doing so will require you to handle the JSON parsing yourself, but will permit to handle to error yourself using a try-catch.
let json;
try {
json = JSON.parse(json);
} catch (e) {
// Handle JSON error.
}
Taken from https://firebase.google.com/docs/functions/http-events

What you're experiencing is not actually a server crash. In fact, technically, by using Cloud Functions, you don't have a server to crash. (For this reason they're called "Serverless Infrastructure") Each request / operation you perform on Cloud Functions is kind of like a brand new server. Which is actually what's fantastic about Cloud Functions in general. (This is an overly simplified explanation, I'd suggest reading up a bit more about it for a better in depth explanation)
That being said, from what I understand you're trying to figure out if the JSON you got is invalid (bad) or not. Occasionally, when I have to hook up a bunch of external services, rarely, but sometimes, they return a bad JSON that my Cloud Functions can't parse, therefore throws an error.
The solution is to put your JSON.parse in to a separate function and a try / catch block like this:
function safelyParseJSON (json) {
var parsed;
try {
parsed = JSON.parse(json);
} catch (e) {
// BAD JSON, DO SOMETHING ABOUT THIS HERE.
}
return parsed; // will be undefined if it's a bad json!
}
function doSomethingAwesome () {
var parsedJSON = safelyParseJSON(data);
// Now if parsedJSON is undefined you know it was a bad one,
// And if it's defined you know it's a good one.
}
With this helper function, if you have to deal with a lot of external JSON resources, you can easily determine if the JSON you're trying to parse is good, and if not, you can at least handle the error your way.
Hope this helps :)

{\n\t"phoneNumber: "9632725300"\n}
From the screenshot, I see that the JSON is invalid or malformed. It contains newline (\n) and tab space (\t) characters. Also, the key "phoneNumber" is not wrapped in double quotes, which again invalidates the JSON.
Here's a valid format of the JSON that the server should receive
{
"phoneNumber": "9632725300"
}

Node.js http.get xml is returned 'escaped'

I am working on a simple AWS Lambda function in Javascript (Node 6.x) which should 'proxy' an RSS of an italian news provider.
This is the code of the function:
var http = require("http")
exports.handler = (event, context, callback) => {
http.get("http://www.milanotoday.it/rss/", (response) => {
response.setEncoding("utf8")
let xml = ""
response.on("data", (chunk) => { xml += chunk })
response.on("end", () => { callback(null, xml) })
})
}
It works, or at least it loads the response inside the xml variable.
I can't get why the string is something like this:
"<?xml version=\"1.0\" encoding=\"UTF-8\" ?>\n<rss version=\"2.0\" xmlns:content=\"http://purl.org/rss/1.0/modules/content/\"...
It seems to be sort of 'escaped'.
Can somebody help me?
Thank you in advance...

http.get is probably working just fine. If you run your code outside of the AWS ecosystem, you'll see that you are getting unescaped XML from http.get. The problem is that Lambda wants you to return JSON so when you pass the string to the callback it gets escaped.
If you are running this function through API Gateway you can do a transform in the integration response. The way to do this is to return an object from your lambda:
callback(null, {myXML: xml}))
Then in the API Gateway go to the integration response area under your GET (or POST) resource and click the arrow next to the 200 response. This should reveal an area for body mappings. You want to add a mapping for application/xml and then add something like:
#set($inputRoot = $input.path('$'))
$inputRoot.myXML
This should get you nice clean XML. It's a little hard to describe so I'll post a screen shot that might help:

Double quotes have to be escaped inside a double quoted string (Makes sense, right?). Now you just have to parse the XML, using for instance xml2js

Uncaught (in promise) SyntaxError: Unexpected end of JSON input

I am trying to send a new push subscription to my server but am encountering an error "Uncaught (in promise) SyntaxError: Unexpected end of JSON input" and the console says it's in my index page at line 1, which obviously is not the case.
The function where I suspect the problem occurring (because error is not thrown when I comment it out) is sendSubscriptionToBackEnd(subscription) which is called in the following:
function updateSubscriptionOnServer(subscription) {
const subscriptionJson = document.querySelector('.js-subscription-json');
const subscriptionDetails = document.querySelector('.js-subscription-details');
if (subscription) {
subscriptionJson.textContent = JSON.stringify(subscription);
sendSubscriptionToBackEnd(subscription);
subscriptionDetails.classList.remove('is-invisible');
} else {
subscriptionDetails.classList.add('is-invisible');
}
}
The function itself (which precedes the above function):
function sendSubscriptionToBackEnd(subscription) {
return fetch('/path/to/app/savesub.php', {
method: 'POST',
headers: {
'Content-Type': 'application/json'
},
body: JSON.stringify(subscription)
})
.then(function(response) {
if (!response.ok) {
throw new Error('Bad status code from server.');
}
return response.json();
})
.then(function(responseData) {
if (!(responseData.data && responseData.data.success)) {
throw new Error('Bad response from server.');
}
});
}
I have tried replacing single quotes with double quotes in the fetch call but that yields the same results.
I know that the JSON should be populated because it prints to the screen in the updateSubscriptionOnServer() function with subscriptionJson.textContent = JSON.stringify(subscription);, and I used that output in the google codelab's example server to receive a push successfully.
EDIT: Here is the JSON as a string, but I don't see a mistake in syntax:
{"endpoint":"https://fcm.googleapis.com/fcm/send/dLmthm1wZuc:APA91bGULRezL7SzZKywF2wiS50hXNaLqjJxJ869y8wiWLA3Y_1pHqTI458VIhJZkyOsRMO2xBS77erpmKUp-Tg0sMkYHkuUJCI8wEid1jMESeO2ExjNhNC9OS1DQT2j05BaRgckFbCN","keys":{"p256dh":"BBz2c7S5uiKR-SE2fYJrjPaxuAiFiLogxsJbl8S1A_fQrOEH4_LQjp8qocIxOFEicpcf4PHZksAtA8zKJG9pMzs=","auth":"VOHh5P-1ZTupRXTMs4VhlQ=="}}
Any ideas??

This might be a problem with the endpoint not passing the appropriate parameters in the response's header.
In Chrome's console, inside the Network tab, check the headers sent by the endpoint and it should contain this:
Example of proper response to allow requests from localhost and cross domains requests
Ask the API developer to include this in the headers:
"Access-Control-Allow-Origin" : "*",
"Access-Control-Allow-Credentials" : true

This happened to me also when I was running a server with Express.js and using Brave browser. In my case it was the CORs problem. I did the following and it solved the problem in my case:
(since this is an Express framework, I am using app.get)
-on the server side:
res.set({
"Content-Type": "application/json",
"Access-Control-Allow-Origin": "*",
});
-on client side I used Fetch to get data but disabled the CORS option
// mode: "no-cors" //disabled this in Fetch
That took care of my issues with fetching data with Express

This can be because you're not sending any JSON from the server
OR
This can be because you're sending invalid JSON.
Your code might look like
res.end();

One of the pitfalls is that returned data that is not a JSON but just a plain text payload regardless of headers set. I.e. sending out in Express via something like
res.send({a: "b"});
rather than
res.json({a: "b"});
would return this confusing error. Not easy to detect in network activity as it looks quite legit.

For someone looking here later. I received this error not because of my headers but because I was not recursively appending the response body to a string to JSON.parse later.
As per the MDN example (I've taken out some parts of their example not immediately relevant):
reader.read().then(function processText({ done, value }) {
if (done) {
console.log("Stream complete");
return;
}
result += chunk;
return reader.read().then(processText);
});
For my issue I had to
Use a named function (not an anonymous ()=>{}) inside the .then
Append the result together recursively.
Once done is true execute something else on the total appended result
Just in case this is helpful for you in the future and your issue is not header related, but related to the done value not being true with the initial JSON stream response.

I know this question has already been answered but just thought I add my thoughts.
This will happen when your response body is empty and response.json() is expecting a JSON string. Make sure that your API is returning a response body in JSON format if must be.

node.js and hapi: fetching data from a database synchronously

Coming from a .net world where synchronicity is a given I can query my data from a back end source such as a database, lucene, or even another API, I'm having a trouble finding a good sample of this for node.js where async is the norm.
The issue I'm having is that a client is making an API call to my hapi server, and from there I need to take in the parameters and form an Elasticsearch query to call, using the request library, and then wait for the instance to return before populating my view and sending it back to the client, problem being is that the request library uses a callback once the data is returned, and the empty view has long been returned to the client by then.
Attempting to place the return within the call back doesn't work since the EOF for the javascript was already hit and null returned in it's place, what is the best way to retrieve data within a service call?
EX:
var request = require('request');
var options = {
url: 'localhost:9200',
path: {params},
body: {
{params}
}
}
request.get(options, function(error, response){
// do data manipulation and set view data
}
// generate the view and return the view to be sent back to client

Wrap request call in your hapi handler by nesting callbacks so that the async tasks execute in the correct logic order. Pseudo hapi handler code is as following
function (request, reply) {
Elasticsearch.query((err, results) => {
if (err) {
return reply('Error occurred getting info from Elasticsearch')
}
//data is available for view
});
}
As I said earlier in your last question, use hapi's pre handlers to help you do async tasks before replying to your client. See docs here for more info. Also use wreck instead of request it is more robust and simpler to use