Serialization of CognitoMigrateUserEvent throws

[ThomasEg]

Describe the bug

Having an event handler for user migration in Cognito:

[assembly: LambdaSerializer(typeof(Amazon.Lambda.Serialization.SystemTextJson.DefaultLambdaJsonSerializer))]
...
public void CognitoMigrateUserHandler(CognitoMigrateUserEvent cognitoEvent, ILambdaContext context)
{
   ...
}

Throws an exception during serialization of CognitoMigrateUserEvent:

Amazon.Lambda.Serialization.SystemTextJson.JsonSerializerException: 
Error converting the Lambda event JSON payload to type Amazon.Lambda.CognitoEvents.CognitoMigrateUserEvent: 
The JSON value could not be converted to System.Boolean. 
Path: $.response.forceAliasCreation | LineNumber: 0 | BytePositionInLine: 401.

The data sent from cognito was:

{
    "version": "1",
    "triggerSource": "UserMigration_Authentication",
    "region": "...",
    "userPoolId": "...",
    "userName": "...",
    "callerContext": {
        "awsSdkVersion": "...",
        "clientId": "..."
    },
    "request": {
        "password": "...",
        "validationData": null,
        "userAttributes": null
    },
    "response": {
        "userAttributes": null,
        "forceAliasCreation": null,
        "enableSMSMFA": null,
        "finalUserStatus": null,
        "messageAction": null,
        "desiredDeliveryMediums": null
    }
}

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

I expect it to serialize correctly and then call the method.

Current Behavior

It throws a deserialization exception.

Reproduction Steps

Setup a Cognito UserPool to have a Migrate user trigger with this target:

[assembly: LambdaSerializer(typeof(Amazon.Lambda.Serialization.SystemTextJson.DefaultLambdaJsonSerializer))]
...
public void CognitoMigrateUserHandler(CognitoMigrateUserEvent cognitoEvent, ILambdaContext context)
{
}

Possible Solution

My guess is that the types of the properties in the response-object needs to be nullable.

Additional Information/Context

No response

AWS .NET SDK and/or Package version used

Amazon.Lambda.CognitoEvents: 4.0.0
Amazon.Lambda.Serialization.SystemTextJson:2.4.4

Targeted .NET Platform

.NET 8

Operating System and version

Windows 11

[peterrsongg]

I was able to reproduce this, seems like making the property nullable is the easiest fix. I have a PR here: #2170

Will bring it up with the team