LambdaAnnotations | Proper use of HttpResults and [FromBody] attribute.

[sergio-asenjo]

Hello!

I've been trying to figure out how to properly use HttpResults returning statement in the "Mock Lambda Test Tool".

As a short example, I've tried this:

[LambdaFunction()]
[HttpApi(LambdaHttpMethod.Get, "/")]
public IHttpResult Test(ILambdaContext context)
{
    return HttpResults.Ok("Ok");
}

Doing so, and returning any type of HttpResults, from the UI of Mock Lambda Test Tool I'm getting a base64 return in response. As for this case, I'm getting:

"eyJzdGF0dXNDb2RlIjoyMDAsImhlYWRlcnMiOnsiY29udGVudC10eXBlIjoidGV4dC9wbGFpbiJ9LCJDb29raWVzIjpudWxsLCJib2R5IjoiT2siLCJpc0Jhc2U2NEVuY29kZWQiOmZhbHNlfQ=="

Which translate to:

{
    "statusCode": 200,
    "headers": {
        "content-type": "text/plain"
    },
    "Cookies": null,
    "body": "Ok",
    "isBase64Encoded": false
}

That's correct overall, but for testing purposes, having to decode the base64 to see what I got it's not what I would want to do recurrently. Is this intended or am I missing something? If I deploy it, through browsers I can get instantly a decoded response.

───

A second thing is that I'm trying to use a [FromBody] attribute to get some data passed in the body, like this:

[LambdaFunction()]
[HttpApi(LambdaHttpMethod.Post, "/")]
public IHttpResult Test([FromBody] Request request, ILambdaContext context)
{
    return HttpResults.Ok("Ok");
}

public class Request
{
    public string Name { get; set; }
}

If through the UI Mock Lambda Test Tool I try to send { "name": "test" }, I get a ValidationException, so it doesn't even enter the Test Function completely.
This is the response (which is also base64 encoded in the UI).

{
    "statusCode": 400,
    "headers": {
        "Content-Type": "application/json",
        "x-amzn-ErrorType": "ValidationException"
    },
    "cookies": null,
    "body": "{\u0022message\u0022: \u00221 validation error(s) detected: Value  at \u0027body\u0027 failed to satisfy constraint: Value cannot be null. (Parameter \u0027json\u0027)\u0022}",
    "isBase64Encoded": false
}

Am I using this correctly for this case? Before trying annotations, I was using the template that comes with Powertools, there I'd just pass the type (in this case would be Request) and I wouldn't get this error.

For both cases, I'm using the base template Serverless Annotation, and deleted what's inside the main Class, everything else is untouched.

[ashishdhingra]

@sergio-asenjo Thanks for starting discussion. The probable reason on why in 1st scenario, Lambda Test tool displays Base64 encoded string is may be because of below generated code behind the scenes:

public System.IO.Stream Test(Amazon.Lambda.APIGatewayEvents.APIGatewayHttpApiV2ProxyRequest __request__, Amazon.Lambda.Core.ILambdaContext __context__)
        {
            // Create a scope for every request,
            // this allows creating scoped dependencies without creating a scope manually.
            using var scope = serviceProvider.CreateScope();
            var functions = scope.ServiceProvider.GetRequiredService<Functions>();

            var httpResults = functions.Test(__context__);
            HttpResultSerializationOptions.ProtocolFormat serializationFormat = HttpResultSerializationOptions.ProtocolFormat.HttpApi;
            HttpResultSerializationOptions.ProtocolVersion serializationVersion = HttpResultSerializationOptions.ProtocolVersion.V2;
            var serializationOptions = new HttpResultSerializationOptions { Format = serializationFormat, Version = serializationVersion };
            var response = httpResults.Serialize(serializationOptions);
            return response;
        }

The IHttpResult interface declares Serialize() method whose return type is Stream. The above generated code invokes the Serialize() method on HttpResult.Ok() return object, which is a Stream and hence Base64 encoded.

For 2nd scenario, in test tool, you need to select API Gateway AWS Proxy in example requests drop down, and modify the body attribute per your needs (working example for your model class below):

{
  "body": "{\"Name\":\"TestName\"}",
  "resource": "/{proxy+}",
  "path": "/path/to/resource",
  "httpMethod": "POST",
  "queryStringParameters": {
    "foo": "bar"
  },
  "pathParameters": {
    "proxy": "path/to/resource"
  },
  "stageVariables": {
    "baz": "qux"
  },
  "headers": {
    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8",
    "Accept-Encoding": "gzip, deflate, sdch",
    "Accept-Language": "en-US,en;q=0.8",
    "Cache-Control": "max-age=0",
    "CloudFront-Forwarded-Proto": "https",
    "CloudFront-Is-Desktop-Viewer": "true",
    "CloudFront-Is-Mobile-Viewer": "false",
    "CloudFront-Is-SmartTV-Viewer": "false",
    "CloudFront-Is-Tablet-Viewer": "false",
    "CloudFront-Viewer-Country": "US",
    "Host": "1234567890.execute-api.{dns_suffix}",
    "Upgrade-Insecure-Requests": "1",
    "User-Agent": "Custom User Agent String",
    "Via": "1.1 08f323deadbeefa7af34d5feb414ce27.cloudfront.net (CloudFront)",
    "X-Amz-Cf-Id": "cDehVQoZnx43VYQb9j2-nvCh-9z396Uhbp027Y2JvkCPNLmGJHqlaA==",
    "X-Forwarded-For": "127.0.0.1, 127.0.0.2",
    "X-Forwarded-Port": "443",
    "X-Forwarded-Proto": "https"
  },
  "requestContext": {
    "accountId": "123456789012",
    "resourceId": "123456",
    "stage": "prod",
    "requestId": "c6af9ac6-7b61-11e6-9a41-93e8deadbeef",
    "identity": {
      "cognitoIdentityPoolId": null,
      "accountId": null,
      "cognitoIdentityId": null,
      "caller": null,
      "apiKey": null,
      "sourceIp": "127.0.0.1",
      "cognitoAuthenticationType": null,
      "cognitoAuthenticationProvider": null,
      "userArn": null,
      "userAgent": "Custom User Agent String",
      "user": null
    },
    "resourcePath": "/{proxy+}",
    "httpMethod": "POST",
    "apiId": "1234567890"
  }
}

CC @normj

Thanks,
Ashish

@github-actions proposed-answer

[github-actions[bot]]

Hello! A team member has marked the above comment as the likely answer to this discussion thread.

• If you agree, please upvote that comment, or click on Mark as answer. I will automatically mark the comment as the answer next time I check.

• If this answer does not help you, please downvote the answer instead and let us know why it was not helpful. I will add a label to this discussion to gain attention from the team.

[normj]

Seeing the base64 is a bug in the mock test tool. I think what is going on is the following block of code from the tool does not have a check in the non Task else block to check if the return is a stream and return it like the first Task if block. So the Stream is accidentally being run the the ILambdaSerializer. @ashishdhingra can you convert this into a issue tag as a bug.

https://github.com/aws/aws-lambda-dotnet/blob/master/Tools/LambdaTestTool/src/Amazon.Lambda.TestTool/Runtime/LambdaExecutor.cs#L184

// If the return was a Task then wait till the task is complete.
if (lambdaReturnObject is Task task)
{
    await task;

    // Check to see if the Task returns back an object.
    // The return type from the Lambda functions MethodInfo must be used for checking if it generic.
    // If you check the type from the object instance returned the non generic Task gets converted
    // by the runtime to Task<VoidTaskResult>.
    if (request.Function.LambdaMethod.ReturnType.IsGenericType)
    {
        var resultProperty = task.GetType().GetProperty("Result", BindingFlags.Public | BindingFlags.Instance);
        if (resultProperty != null)
        {
            var taskResult = resultProperty.GetMethod.Invoke(task, null);
            if (taskResult is Stream stream)
            {
                lambdaReturnStream = stream;
            }
            else
            {
                lambdaReturnStream = new MemoryStream();
                MakeGenericSerializerCall(request.Function.Serializer, taskResult, lambdaReturnStream);
            }
        }
    }
}
else
{
    lambdaReturnStream = new MemoryStream();
    MakeGenericSerializerCall(request.Function.Serializer, lambdaReturnObject, lambdaReturnStream);
}

[ashishdhingra]

Opened issue #1576 from this discussion. Closing this discussion.

[github-actions[bot]]

Hello! Reopening this discussion to make it searchable.