feat: Support Ruby handlers with :: in path definition

[njyjn]

Description

This enhancement adds support for Ruby handlers that have namespace resolution operators (::) in their path definition, e.g. handler: 'src/lambdas/examples/hello.Hello::Handler.process', etc. This was officially mentioned in the AWS documentation (see below). Logic was preserved for existing scenarios (without ::) to reduce the risk of regression.

Without this enhancement, the following error message is triggered when the handler is invoked

offline: Failure: Command failed with exit code 1: ruby /PATH_TO_PROJECT/node_modules/serverless-offline/dist/lambda/handler-runner/ruby-runner/invoke.rb src/functions/source.LambdaFunctions::Handler process
~/.rbenv/versions/2.7.1/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:92:in `require': cannot load such file -- ./src/functions/source.LambdaFunctions::Handler (LoadError)

This seems to be because the handler paths and names are not being split correctly. For such Ruby handlers, the name should have the resolution operator instead of the path. Support for this already seems to be built-in

serverless-offline/src/lambda/handler-runner/ruby-runner/invoke.rb

Lines 75 to 78 in d319174

	# handler name is either a global method or a static method in a class
	# my_method or MyModule::MyClass.my_method
	handler_method, handler_class = handler_name.split(".").reverse
	handler_class ||= "Kernel"

Motivation and Context

AWS officially demonstrates the use of handler methods within modules and classes. The specific example given is

module LambdaFunctions
  class Handler
    def self.process(event:,context:)
      "Hello!"
    end
  end
end

where the handler setting is source.LambdaFunctions::Handler.process. Since this is the entry point for many developers, it would be great if it is supported by serverless-offline.

For projects that implement a large number of handlers, it would be optimal to not pollute the Kernel private_method namespace if such handlers can be encapsulated into their own modules and classes.

Resolves #1031

How Has This Been Tested?

Unit tests were added in 4a6d0dc to validate this enhancement, as well as the original functionality that was left in tact.

In addition to the additional unit tests, I was able to use serverless-offline for Ruby handlers with and without namespace separators

"serverless.ts"

  functions: {
    hello: {
      environment: {
        GEM_PATH: 'vendor/bundle/ruby/2.7.0/',
      },
      handler: 'src/lambdas/examples/hello.Hello::Handler.process',
      events: [
        {
          http: {
            path: '/hello',
            method: 'post',
            request: {
              schema: {
                'application/json': "${file(schemas/examples/hello.json)}"
              },
            },
          }
        }
      ]
    },
    hello2: {
      environment: {
        GEM_PATH: 'vendor/bundle/ruby/2.7.0/',
      },
      handler: 'src/lambdas/examples/hello2.handler',
      events: [
        {
          http: {
            path: '/hello2',
            method: 'post',
            request: {
              schema: {
                'application/json': "${file(schemas/examples/hello2.json)}"
              },
            },
          }
        }
      ]
    }
  }
...

Built locally using package.json and compiled used Babel per the contribution guide.

Please let me know if you have any questions or if there is something I can improve on. Thanks!

Edit: Added more details on the current way serverless-offline is failing to invoke such handlers. Clarified that as long as the path string contains ::, the enhancement will take effect.

Screenshots (if appropriate):

[SirFixAL0t]

This feature would be really helpful for teams that have unit tests build around multiple lambda functions. Without handling handlers in classes, the alternative is having lambda handlers in the global scope which causes scope creep of some functions resulting in false positives and blocking issues for ruby lambdas.

Thanks!

[pgrzesik]

Thank you @njyjn for submitting this PR. It looks good, well done 🙇