• What was the config you used?

functions:
  myFunction:
    handler: handler.myFunction
    events:
      - http:
          ...
          authorizer:
            arn: { "Fn::Join" : [ ":", [ "arn:aws:lambda", { "Ref" : "AWS::Region" }, { "Ref" : "AWS::AccountId" }, "function:myAuthorizer" ] ] }
            ...

• What stacktrace or error message from your provider did you see?

Serverless: Packaging service...

  Type Error ---------------------------------------------

     functionArn.split is not a function

     For debugging logs, run again after setting the "SLS_DEBUG=*" environment variable.

  Get Support --------------------------------------------
     Docs:          docs.serverless.com
     Bugs:          github.com/serverless/serverless/issues

     Please report this error. We think it might be a bug.

  Your Environment Information -----------------------------
     OS:                 darwin
     Node Version:       4.3.2
     Serverless Version: 1.6.1

Similar or dependent issues:

• Bug Report : Not be able to use Fn::ImportValue or Ref in the Authorizer section of a File in *.YAML File #3129

Additional Data

• Serverless Framework Version you're using: 1.6.1
• Operating System: macOS Sierra 10.12.3

Proposed solution:

This report signals two issues:

1. Messed up error reporting (functionArn.split is not a function)

No need to do anything here, as such errors will be handled neatly, once schema is configured for this event (see: #8018)

2. No support for CF intrinsic functions at authorizer.arn.

See: #3212 (comment)

1. When arn is passed in object form, require name property (validate it's existence inline, at least it might be hard to validate it with schema, and receive human friendly error message).
2. When arn is passed in string form and no name is passed. deprecate name resolution with message that it won't be auto-resolved in next major and to have authorizer named, name has to be explicitly set in config