SQS Event Source on Alias has race condition

[sam-goodwin]

If you create a SQS event source pointing at an Alias, CFN won't wait for the Alias to be created before attempting to create the event source mapping, causing the stack to fail.

Repro:

const fn = new lambda.Function(this, 'Function', {
  code: lambda.Code.inline('exports.handler = function() { return "hello"; }'),
  handler: 'index.handler',
  runtime: lambda.Runtime.NodeJS810
});
const version = fn.addVersion('1');
const alias = new lambda.Alias(this, 'Alias', {
  version,
  aliasName: 'test'
});

const queue = new sqs.Queue(this, 'Queue');
alias.addEventSource(new event_sources.SqsEventSource(queue));

Error:

Function does not exist (Service: AWSLambda; Status Code: 400; Error Code: InvalidParameterValueException;

[eladb]

What's the solution?

[rix0rrr]

How can this be true? Doesn't the event source refer to the alias ARN?

[sam-goodwin]

@RomainMuller identified that it's because the alias's ARN is created with a Fn:Join, so we can fix that or add a dependency (ew).