When testing HttpApi in local, queryStringParameters should be either undefined or non-empty

[mastazi]

Description:

I have this function:

fakeFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: src/handlers/handlers.fake
      Description: A Lambda function.
      Events:
        Api:
          Type: HttpApi
          Properties:
            Path: /my-path/
            Method: get

When I test this in local, even if I call the function without any queryString parameters, the event object still has the property queryStringParameters. However, after deployment, the property is not created at all.

so as an example, if my function was in Node.js, attempting this check: if (event.queryStringParameters.hasOwnProperty('myproperty')){...} will work in SAM local, but after deployment will result in the error “cannot read property ‘myproperty’ of undefined”.

the only way it would work after deployment, is this:
if (event.hasOwnProperty('queryStringParameters') && event.queryStringParameters.hasOwnProperty('myproperty'))

I think the emulator should work in the same way as "real world" Api Gateway, so queryStringParameters should be either undefined or non-empty.

Steps to reproduce:

1. create a function defined as in the template.yml snippet above, then include this check in the function:

if (event.queryStringParameters.hasOwnProperty('myproperty')) {
  console.log("checking)
}

2. run sam local start-api and call the function without any query string parameters. It will work.
3. deploy the function, then call it without any query string parameters. You will get 500 error.

Observed result:

Go to CloudWatch and check the function logs after completing step 3 above.
In CloudWatch you will find an error message such as the one below:

{
    "errorType": "TypeError",
    "errorMessage": "Cannot read property 'hasOwnProperty' of undefined",
    "stack": [
        "TypeError: Cannot read property 'hasOwnProperty' of undefined",
        "    at Runtime.exports.fakeFunction [as handler] (/var/task/src/handlers/handlers.js:43:37)",
        "    at processTicksAndRejections (internal/process/task_queues.js:95:5)"
    ]
}

However there will be no error when executing the function locally, as observed at point 2 above.

Expected result:

The expected result is that the same error "Cannot read property 'hasOwnProperty' of undefined" should also be thrown in local simulator.

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

1. OS: Windows 10
2. sam --version: SAM CLI, version 1.23.0
3. AWS region: ap-southeast-2

[jfuss]

@mastazi Thanks for the report. We do try to replicate what we can from the "real" API Gateway. It looks like this might be caused by

aws-sam-cli/samcli/local/events/api_event.py

Line 411 in 234655e

"queryStringParameters": self.query_string_params,

. Compare this to what what we do for Rest:

aws-sam-cli/samcli/local/events/api_event.py

Line 231 in 234655e

"queryStringParameters": dict(self.query_string_params) if self.query_string_params else None,

. So we might need the same logic in the V2 version.

Updating labels

[mastazi]

@jfuss thanks for identifying the code responsible for it, yes I agree looks like the if ... else None will do the trick here.

[tomatod]

This seems has been fixed in #3497.
I did not reproduce this issue #3018 with version 1.40.0.

[super132]

Since PR #3497 fixed the issue, I'm closing it now.