Multiple queryStringParameters ignored in sam local start-api for HTTP APIs

[EpicSquid]

Description:

I have a simple lambda function which takes multiple query string parameters, however only the last query string parameter is kept.

Steps to reproduce:

I have defined a function as follows:

TestFunction:
    Type: AWS::Serverless::Function 
    Properties:
      CodeUri: rest_api/test/
      Events:
        GetTest:
          Type: HttpApi
          Properties:
            Path: /api/test
            Method: get

Then run the application with sam local start-api --debug

Then sent a query to it using postman as a GET request: http://localhost:3000/api/test?test_ids=1&test_ids=2

Observed result:

The event output for the function is the following

Constructed String representation of Event Version 2.0 to invoke Lambda. Event: 
{
  "version": "2.0",
  "routeKey": "GET /api/test",
  "rawPath": "/api/test",
  "rawQueryString": "test_ids=1&test_ids=2",
  "cookies": [],
  "headers": {
    "Content-Type": "application/json",
    "User-Agent": "PostmanRuntime/7.28.3",
    "Accept": "*/*",
    "Postman-Token": "cb0df40e-920d-4f8d-bbf8-9381f9ee5e45",
    "Host": "localhost:3000",
    "Accept-Encoding": "gzip, deflate, br",
    "Connection": "keep-alive",
    "Content-Length": "21",
    "X-Forwarded-Proto": "http",
    "X-Forwarded-Port": "3000"
  },
  "queryStringParameters": {
    "test_ids": "2"
  },
  "requestContext": {
    "accountId": "123456789012",
    "apiId": "1234567890",
    "http": {
      "method": "GET",
      "path": "/api/test",
      "protocol": "HTTP/1.1",
      "sourceIp": "127.0.0.1",
      "userAgent": "Custom User Agent String"
    },
    "requestId": "46b22e74-8e33-4f90-8f5c-3af887356c8e",
    "routeKey": "GET /api/test",
    "stage": null
  },
  "body": "",
  "pathParameters": {},
  "stageVariables": null,
  "isBase64Encoded": false
}

Critically:

"queryStringParameters": {
    "test_ids": "2"
  },

Expected result:

I expected the following parsing for the queryStringParameters, as per the documentation

"queryStringParameters": {
    "test_ids": "1,2"
  },

Additional environment details (Ex: Windows, Mac, Amazon Linux etc)

1. OS: Windows 10
2. sam --version: 1.29.0
3. AWS region: ap-southeast-2

Add --debug flag to command you are running

[ssenchenko]

Doesn't it work only with sam local? When you run it on AWS everything is okay isn't it?

[EpicSquid]

Correct, this works totally fine running on AWS, but does not work locally. Just double checked and cloudwatch logs say the request correctly gets the multiple query string parameters as expected

[jlapier]

Can confirm, I observed the same behavior when using an HTTP API: the extra values are dropped and the event only contains the first parameter.

[ssenchenko]

Solution merged. Closing