Aws-sam-cli: Function returned an invalid response (must include one of: body, headers or statusCode in the response object).

[luillyfe]

Description

I am trying to test my local function with sam local start-api but it appears to make an useless validation to the response. And since the code above works on perfectly when I submitted to aws lambda, I cannot see the real value of that validation and it does not allow me to test the function in local

Steps to reproduce

create your function and return an array, let's say

 index.handler = async () => {
    return [
        {"key":"jsandjsnckads","name":"name1"}, 
        {"key":"asjncjaNCJKndsc","name":"name2"}
    ];
};

execute sam local start-api
go to http://127.0.0.1:3000/users

Observed result

brwoser output
no data

console output

 Function returned an invalid response (must include one of: body, headers or statusCode in the response object). Response received: [
        {"key":"jsandjsnckads","name":"name1"}, 
        {"key":"asjncjaNCJKndsc","name":"name2"}
    ]

Expected result

browser output

[
        {"key":"jsandjsnckads","name":"name1"}, 
        {"key":"asjncjaNCJKndsc","name":"name2"}
    ]

no console output

[jfuss]

@luillyfe This is not useless validation. According to API Gateway Docs, the Lambda must return a specific json format. More details can be found here and here.

Closing as the validation matches API Gateways expectations.

[rsibanez89]

@luillyfe did you solve this problem?
I'm having the same issue. This is my handler:

public APIGatewayProxyResponse Handle() => new APIGatewayProxyResponse
{
    Body = "The lambda function is working!",
    StatusCode = 200,
    Headers = new Dictionary<string, string>
    {
        { "Content-Type", "application/json" },
        { "Access-Control-Allow-Origin", "*" }
    }
};

This is the error:
2019-05-31 16:00:15 Invalid API Gateway Response Keys: {'multiValueHeaders'} in {'statusCode': 200, 'headers': {'Content-Type': 'application/json', 'Access-Control-Allow-Origin': '*'}, 'multiValueHeaders': None, 'body': 'The lambda function is working!', 'isBase64Encoded': False} 2019-05-31 16:00:15 Function returned an invalid response (must include one of: body, headers or statusCode in the response object). Response received: {"statusCode":200,"headers":{"Content-Type":"application/json","Access-Control-Allow-Origin":"*"},"multiValueHeaders":null,"body":"The lambda function is working!","isBase64Encoded":false} 2019-05-31 16:00:15 127.0.0.1 - - [31/May/2019 16:00:15] "GET / HTTP/1.1" 502 - 2019-05-31 16:00:15 127.0.0.1 - - [31/May/2019 16:00:15] "GET /favicon.ico HTTP/1.1" 403

[rsibanez89]

I solved it by downgrading the SAM CLI version to 0.15.0

sam local start-api doesn't work on SAM CLI v0.16.1. However, if you deploy it to AWS you won't get the error.

[luillyfe]

@rsibanez89 sorry for the late answer. I am glad it is working for you now. The thing to keep in mind here is the Output Format of a Lambda Function for Proxy Integration requires that validation but when we are in the console we do not normally (by default) mark the Lambda proxy integration checkbox. That is why it behaves differently from AWS Console to local-api server. I hope this clarify a little bit this topic.

[sukumarbarman]

Hi rsibanez89,
I am also facing same issue for version 0.19.0. But I tried to download SAM CLI version to 0.15.0. But did not get link. Can you please provide the link.

Regards,
Sukumar

[sukumarbarman]

@luillyfe ,
I did not get your solution. What changes you did in the following handler:
public APIGatewayProxyResponse Handle() => new APIGatewayProxyResponse
{
Body = "The lambda function is working!",
StatusCode = 200,
Headers = new Dictionary
{
{ "Content-Type", "application/json" },
{ "Access-Control-Allow-Origin", "*" }
}
};

[rsibanez89]

@sukumarbarman These are my steps:
https://github.com/rsibanez89/aws-projects/tree/master/SAMApiGatewayLambda

[sukumarbarman]

@rsibanez89 Thanks for your reply. Tried to install SAM CLI version 0.15.0. But I did not get the link to download. Can you please provide the link.

[rsibanez89]

@sukumarbarman Check all the releases here: https://github.com/awslabs/aws-sam-cli/releases

[ianpogi5]

@rsibanez89 sorry for the late answer. I am glad it is working for you now. The thing to keep in mind here is the Output Format of a Lambda Function for Proxy Integration requires that validation but when we are in the console we do not normally (by default) mark the Lambda proxy integration checkbox. That is why it behaves differently from AWS Console to local-api server. I hope this clarify a little bit this topic.

How can we disable response validation in sam local start-api?

[chunkjs]

In my case I upgraded to the latest version (0.22), that did the trick 🌬 🏆

brew upgrade aws-sam-cli

[BJCheng]

@rsibanez89 sorry for the late answer. I am glad it is working for you now. The thing to keep in mind here is the Output Format of a Lambda Function for Proxy Integration requires that validation but when we are in the console we do not normally (by default) mark the Lambda proxy integration checkbox. That is why it behaves differently from AWS Console to local-api server. I hope this clarify a little bit this topic.

From the AWS 'Running API Gateway Locally' tutorial it says 'By default, AWS SAM uses Proxy Integration'. Since you already assume our confuse of why AWS Console to local-api server behaves differently, so would you mind share how to uncheck the Running API Gateway Locally?