bs-aws-lambda

bs-aws-lambda is a set of types to use when creating AWS lambda handlers.

Those types are inspired by the @types/aws-lambda package with typescript types.

Installation

yarn add @ahrefs/bs-aws-lambda

or to follow the master version:

yarn add https://github.com/ahrefs/bs-aws-lambda.git

Usage

Add @ahrefs/bs-aws-lambda to the bs-dependencies of bsconfig.json.

Then when you create a function handler for a lambda, you can annotate it with one of AwsLambda.Scheduled.handler, AwsLambda.Dynamodb.streamHandler, AwsLambda.Sns.handler, etc. This way you are sure to expose a function which respect the signature expected by Lambda and you get types information for all the parameters this function will receive.

Example

A full example is documented here. It is using the sources from the example directory.

Simple echo function for the API Gateway. This might seem a little verbose compare to a typescript version. But using this package, you are sure to handle all the possible cases where a value is actually null or base64 encoded. Plus the returned object given to the callback will always have the expected fields and types.

let handler: AwsLambda.APIGatewayProxy.handler =
  (event, _context, cb) => {
    open AwsLambda.APIGatewayProxy;
    let parameter =
      event
      |. Event.queryStringParameters
      |> Js.Option.andThen((. params) => Js.Dict.get(params, "userid"));
    switch (parameter) {
    | Some(userid) => Js.log2("executing lambda for", userid)
    | None => Js.log("executing lambda for anonymous user")
    };
    let result =
      switch (event |. Event.body) {
      | None =>
        Js.log("error: no body available in the request");
        result(
          ~body=`Plain({|{"status": "no body available in the request"}|}),
          ~statusCode=400,
          (),
        );
      | Some(body) =>
        Result.make(~statusCode=200, ~body, ~isBase64Encoded=event |. Event.isBase64Encoded, ())
      };
    cb(Js.null, result);
    Js.Promise.resolve();
  };

let handler: AwsLambda.APIGatewayProxy.handler =
  fun event  ->
    fun _context  ->
      fun cb  ->
        let open AwsLambda.APIGatewayProxy in
          let parameter =
            (event |. Event.queryStringParameters) |>
              (Js.Option.andThen
                 ((fun params  -> Js.Dict.get params "userid")[@bs ])) in
          (match parameter with
           | ((Some (userid))[@explicit_arity ]) ->
               Js.log2 "executing lambda for" userid
           | None  -> Js.log "executing lambda for anonymous user");
          (let result =
             match event |. Event.body with
             | None  ->
                 (Js.log "error: no body available in the request";
                  result
                    ~body:(`Plain
                             {|{"status": "no body available in the request"}|})
                    ~statusCode:400 ())
             | ((Some (body))[@explicit_arity ]) ->
                 Result.make ~statusCode:200 ~body
                   ~isBase64Encoded:(event |. Event.isBase64Encoded) () in
           cb Js.null result; Js.Promise.resolve ())

The typescript equivalent of the type annotation is actually more verbose:

export const handle: Lambda.APIGatewayProxyHandler = async (
    event: Lambda.APIGatewayEvent,
    context: Lambda.Context,
    cb: Lambda.APIGatewayProxyCallback) => {
}

bs-aws-lambda

Installation

Usage

Example

Project

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