CfnFunction Not Initializing Event Source Properties for Api Event

[SherMM]

🐛 Bug Report

What is the problem?

I am trying to build a lambda-backed API gateway, but instead of using the Lambda and API GW constructs, I am using aws_sam.CfnFunction and aws_sam.CfnApi, due to my use case. I was able to build and deploy the lambda function, but when I started adding the API to it using CfnApi, I am unable to get things initialized as expected. When I attempt to initialize the events parameter of the aws_sam.CfnFunction object, the "Properties" key, nested under the "Events" key, is just an empty pair of brackets, and not the expected, initialized "Path", "Method", and "RestApiId" keys. I have attempted to initialize this multiple ways, but none have worked so far.

Reproduction Steps

echo_api = aws_sam.CfnApi(
    self,
    "EchoApi",
    stage_name=<stage-name>,
    definition_body=<swagger-definition>
)

echo_lambda = aws_sam.CfnFunction(
    self,
    "EchoLambda",
    code_uri=aws_sam.CfnFunction.S3LocationProperty(
        bucket=<bucket-string>,
        key=<key-string>,
    runtime=_lambda.Runtime.PYTHON_3_6.to_string(),
    handler="lambda/echo.handler",
    description="An example lambda that echos a message",
    events={
        "Echo": aws_sam.CfnFunction.EventSourceProperty(
            properties=aws_sam.CfnFunction.ApiEventProperty(
                method="get",
                path="/echo",
                rest_api_id=echo_api.logical_id
            ),
            type="Api"
        )
    }
)

Verbose Log

"Handler": "lambda/echo.handler",
"Runtime": "python3.6",
"Description": "An example lambda that echos a message",
"Events": {
    "Echo": {
    "Properties": {},
    "Type": "Api"
    }
}

Environment

• CDK CLI Version: 1.0.0
• Module Version: 1.4
• OS: Linux RHEL
• Language: Python

Other information

[nija-at]

This seems to be a Python specific problem. I'm able to reproduce this with Python running CDK version 1.9.0 but not Typescript.

This seems to occur for not just ApiEventProperty but also S3EventProperty (see Py snippet below) and probably for others.

This is my working typescript code -

#!/usr/bin/env node
import cdk = require('@aws-cdk/core');
import sam = require('@aws-cdk/aws-sam');

const app = new cdk.App();
const stack = new cdk.Stack(app, 'mystack');

new sam.CfnFunction(stack, 'myfunction', {
  codeUri: {
    bucket: 'b', key: 'k'
  },
  runtime: 'nodejs10.x',
  handler: 'index.handler',
  events: {
    'echo': {
      type: 'api',
      properties: {
        method: 'get',
        path: '/echo'
      }
    }
  }
});

app.synth();

And this is the Python CDK app where I could replicate this issue -

#!/usr/bin/env python3

from aws_cdk import (
    core,
    aws_sam as sam
)

app = core.App()
stack = core.Stack(app, "hello-cdk")
api = sam.CfnApi(
    stack,
    "myapi",
    name="myapi",
    stage_name="mystagename",
)

fn = sam.CfnFunction(
    stack,
    "myfn",
    code_uri=sam.CfnFunction.S3LocationProperty(
        bucket="b",
        key="k"
    ),
    runtime="nodejs10.x",
    handler="index.handler",
    events={
        "echo": sam.CfnFunction.EventSourceProperty(
            properties=sam.CfnFunction.ApiEventProperty(
                method="get",
                path="/echo",
                #rest_api_id=api.logical_id
            ),
            type="Api"
        ),
        "s3": sam.CfnFunction.EventSourceProperty(
            properties=sam.CfnFunction.S3EventProperty(
                bucket="b",
                events=["1"]
            ),
            type="aaa"
        )
    }
)

app.synth()

The output CF template had empty Properties bags against the events key

...
        "Handler": "index.handler",
        "Runtime": "nodejs10.x",
        "Events": {
          "echo": {
            "Properties": {},
            "Type": "Api"
          },
          "s3": {
            "Properties": {},
            "Type": "aaa"
          }
        }
...

[RomainMuller]

The same problem happens in Java:

package com.myorg;

import java.util.Arrays;

import com.google.common.collect.ImmutableMap;

import software.amazon.awscdk.core.App;
import software.amazon.awscdk.core.Stack;
import software.amazon.awscdk.services.sam.CfnFunction;
import software.amazon.awscdk.services.sam.CfnFunction.ApiEventProperty;
import software.amazon.awscdk.services.sam.CfnFunction.EventSourceProperty;
import software.amazon.awscdk.services.sam.CfnFunction.S3EventProperty;
import software.amazon.awscdk.services.sam.CfnFunction.S3LocationProperty;
import software.amazon.awscdk.services.sam.CfnFunctionProps;

public class HelloApp {
    public static void main(final String argv[]) {
        final App app = new App();
        final Stack stack = new Stack(app, "mystack");

        final CfnFunctionProps functionProps =
                CfnFunctionProps.builder()
                                .codeUri(S3LocationProperty.builder().bucket("b").key("k").build())
                                .runtime("nodejs10.x")
                                .handler("index.handler")
                                .events(ImmutableMap.of("echo",
                                                        EventSourceProperty.builder()
                                                                           .type("Api")
                                                                           .properties(ApiEventProperty.builder()
                                                                                                       .method("get")
                                                                                                       .path("/echo")
                                                                                                       .build())
                                                                           .build(),
                                                        "s3",
                                                        EventSourceProperty.builder()
                                                                           .type("aaa")
                                                                           .properties(S3EventProperty.builder()
                                                                                                      .bucket("b")
                                                                                                      .events(Arrays.asList("1"))
                                                                                                      .build())
                                                                           .build()))
                                .build();
        new CfnFunction(stack, "myfunction", functionProps);

        app.synth();
    }
}

[RomainMuller]

Found this to be caused by a bug in the jsii kernel (aws/jsii#822).