Help required: Cognito callback function signature

[chippyash]

I'm writing a Cognito pre token generation lambda using bref. The docs at https://docs.aws.amazon.com/cognito/latest/developerguide/user-pool-lambda-pre-token-generation.html suggest that the callback is called with 2 parameters. If I do that in php e.g.

$callback(null, $event);

then I get an error :

{
    "errorType": "ArgumentCountError",
    "errorMessage": "Too few arguments to function {closure}(), 2 passed in /var/task/vendor/bref/bref/src/Runtime/LambdaRuntime.php on line 109 and exactly 3 expected",
    "stack": [
        "#0 /var/task/vendor/bref/bref/src/Runtime/LambdaRuntime.php(109): {closure}()",
        "#1 /opt/bref/bootstrap.php(38): Bref\\Runtime\\LambdaRuntime->processNextEvent()",
        "#2 {main}"
    ]
}

I also looked at https://aws.amazon.com/blogs/mobile/how-to-use-cognito-pre-token-generators-to-customize-claims-in-id-tokens/ and simply returned the event which leads to the same error being thrown.

Does anyone know what that callback signature should be for PHP as the node/python examples don't translate.

[mnapoli]

I think you need to return $event.

[nephele42]

Did anyone test this? I have tried returning $event, and many other versions but cognito always fails with invalid lambda response.

[hmimthiaz]

@chippyash I am trying to do merge the social account with existing user. Account creation all works and when the authentication process starts it end with the message in the client callback url.

@nephele42 did you succeed with this. I get the same error "Unrecognizable+lambda+output"

[nephele42]

@hmimthiaz no I did not, gave up and wrote the lambda in node.

[hmimthiaz]

@nephele42 thanks for the update. I did raise this issue in bref slack community and no response.

Cognito trigger is expecting valid response for the continuation of events. I went mad for two days.

I gave up and updated the app in node 😂

Nice article on merging identities on Coginto - https://www.codewithyou.com/blog/how-to-link-a-cognito-account-with-a-google-accountfull-stack