Typed input and output

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Hi! I am trying to get rid of JSON.parse(input) and JSON.dump(output) in activities/workflows and wanted to define Input and Output classes with dry-struct to define the structure.

Then I found this line in https://github.com/coinbase/temporal-ruby/blob/master/lib/temporal/concerns/typed.rb#L22

unless klass.is_a?(Dry::Types::Type)

Now I am stuck on how to make reusable structs with validation for workflow/activity params. I have three questions:

1. Does it make sense to change condition in typed.rb to allow dry structs?
2. How I can add typed output, so I don't need to serialize and deserialize outputs multiple time?
3. Any best practices to validate inputs before activating the workflow?

Any ideas how to solve this?

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For now I monkeypatched typed.rb with

module Temporal
  module Concerns
    module Typed
      module ClassMethods
        attr_reader :output_class

        def execute_in_context(context, input)
          if input_class
            input = input.first if input.is_a?(Array) && input.size == 1
            input = input_class.new(input)
          end
          output = super(context, input)
          return output unless output_class
          output_class.new(output)
        end

        def input(klass = nil, &block)
          if klass
            unless klass.is_a?(Dry::Types::Type) || klass << Dry::Struct
              raise 'Unsupported input class. Use one of the provided Temporal::Types'
            end
            @input_class = klass
          else
            @input_class = generate_struct
            @input_class.instance_eval(&block)
          end
        end

        def output(klass = nil, &block)
          if klass
            unless klass.is_a?(Dry::Types::Type) || klass << Dry::Struct
              raise 'Unsupported output class. Use one of the provided Temporal::Types'
            end
            @output_class = klass
          else
            @output_class = generate_struct
            @output_class.instance_eval(&block)
          end
        end

        private

        def generate_struct
          # TODO: Get rid of deprecation warning
          Class.new(Dry::Struct::Value) { transform_keys(&:to_sym) }
        end
      end
    end
  end
end

Would it be good to create PR with this?

[cdimitroulas]

Why do you need JSON.parse/JSON.dump in activities and workflows? There shouldn't be any need to do that 🤔

If you return hashes from activities/workflows, those are already handled automatically by the library. We simply use hashes (with string keys instead of symbols) for all activity inputs/outputs and it works fine.