APIGW Response using Lambda custom (non-proxy) integration

[ymwjbxxq]

Hello all,

we have 2 libs:

• lambda_http
• lambda_runtime

And you cannot mix them, and I have a third, and I can only solve with lambda_runtime and try to return a lambda_http response.

PROBLEM:
My APIGW has a Lambda Request Authorizer. The output of the Authorizer is a context, for example:
context: { email: a@a.com }

To pass the context to Lambda, you must disable the LambdaProxy and create an integration template.
Using the default one from AWS, I end up having a payload that is not compatible with the types of lambda_http
Because of this, I need to create my custom structure and switch to lambda_runtime.

LINKS:

• https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-lambda-authorizer-output.html
• https://aws.amazon.com/premiumsupport/knowledge-center/custom-headers-api-gateway-lambda/#:~:text=To%20pass%20custom%20headers%20from,from%20the%20original%20API%20request

#[derive(Debug, Serialize, Deserialize)]
pub struct Payload {
    #[serde(rename = "auth")]
    #[serde(skip_serializing_if = "Option::is_none")]
    pub auth: Option<Auth>,

    #[serde(rename = "body")]
    pub body: HashMap<String, Value>,

    #[serde(rename = "params")]
    #[serde(skip_serializing_if = "Option::is_none")]
    pub params: Option<Params>,
}

The Lambda become :

 lambda_runtime::run(service_fn(|event: LambdaEvent<Value>| {
        execute(event)
    }))
    .await?;
...

pub async fn execute(event: LambdaEvent<Value>) -> Result<Value, Error> {
     let request = MyStruct::deserialize(MapDeserializer::new(result.body.into_iter())).unwrap();
    ...my code...
    
    Ok(response)

The problem is the response. End of the day, I need to return something like the:

{
  "statusCode": 200,
  "body": "ok",
  "headers": { 
    "Access-Control-Allow-Origin": "*",
    ...
    "Accept": "application/json"
  }
}

If I use:
serde_json::from_str(response)?

It will return all as JSON in the body, and so it will skip the headers (see images)

Question is:

• how can I do it?

If I return Result<Response<String>, Error lambda_runtime complain

 the trait bound `lambda_http::Response<std::string::String>: Serialize` is not satisfied
the following other types implement trait `Serialize`:

[jdisanti]

I think you will have better luck asking this in https://github.com/awslabs/aws-lambda-rust-runtime

[ymwjbxxq]

OK I did it
awslabs/aws-lambda-rust-runtime#548

[github-actions[bot]]

Hello! Reopening this discussion to make it searchable.