feat(plugin/aws-lambda)accept string type statusCode as return when working in proxy integration mode

[windmgc]

Summary

Hi, I would like to add some compatibility to Kong's aws-lambda plugin so that it can receive string type status code when working in the proxy integration mode.

When AWS Lambda function is working as a proxy integration, the statusCode returned by lambda function will become the HTTP status code returned by API gateway.

Currently, we only accept number type statusCode,

kong/kong/plugins/aws-lambda/handler.lua

Line 75 in 23f50ea

if type(response.statusCode) ~= "number" then

After some tests I found that AWS API gateway works fine if the type of statusCode is either number or string. And if the statusCode is an invalid HTTP status code, such as 600(smaller than 100 or larger than 599) or 200a(containing non-numeric characters), it will throw an "internal server error".

It would be good for us to be compatible with a string type status code, according to FTI-4014.

Full changelog

• Add a feature that make aws-lambda handler be compatible with string type statusCode
• Add validation function to check if the statusCode is legal

Issue reference

Fix FTI-4014

[CLAassistant]

All committers have signed the CLA.

[fffonion]

🎉 First PR!

[ms2008]

LGTM

[windmgc]

@dndx Could you review the PR again? Thanks!

[dndx]

This should be moved inside the if block above, if the status_code is not string then there is no reason to check it again here.

[windmgc]

Fixed

I wonder if it needs more strict check on types, like

  if type(status_code) == "string" or type(status_code) == "number" then
    status_code = tonumber(status_code)

    if not status_code then
      return false
    end

  else
    -- Validation failed if status code is not string or number
    return false
  end
  
  end