Module: T::Props::Private::DeserializerGenerator

Extended by:
Sig
Defined in:
lib/types/props/private/deserializer_generator.rb

Overview

Generates a specialized ‘deserialize` implementation for a subclass of T::Props::Serializable.

The basic idea is that we analyze the props and for each prop, generate the simplest possible logic as a block of Ruby source, so that we don’t pay the cost of supporting types like T:::Hash[CustomType, SubstructType] when deserializing a simple Integer. Then we join those together, with a little shared logic to be able to detect when we get input keys that don’t match any prop.

Class Method Summary collapse

Methods included from Sig

sig

Class Method Details

.generate(props, defaults) ⇒ Object

[View source]

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# File 'lib/types/props/private/deserializer_generator.rb', line 31

def self.generate(props, defaults)
  stored_props = props.reject {|_, rules| rules[:dont_store]}
  parts = stored_props.map do |prop, rules|
    # All of these strings should already be validated (directly or
    # indirectly) in `validate_prop_name`, so we don't bother with a nice
    # error message, but we double check here to prevent a refactoring
    # from introducing a security vulnerability.
    raise unless T::Props::Decorator::SAFE_NAME.match?(prop.to_s)

    hash_key = rules.fetch(:serialized_form)
    raise unless T::Props::Decorator::SAFE_NAME.match?(hash_key)

    ivar_name = rules.fetch(:accessor_key).to_s
    raise unless ivar_name.start_with?('@') && T::Props::Decorator::SAFE_NAME.match?(ivar_name[1..-1])

    transformation = SerdeTransform.generate(
      T::Utils::Nilable.get_underlying_type_object(rules.fetch(:type_object)),
      SerdeTransform::Mode::DESERIALIZE,
      'val'
    )
    transformed_val = if transformation
      # Rescuing exactly NoMethodError is intended as a temporary hack
      # to preserve the semantics from before codegen. More generally
      # we are inconsistent about typechecking on deser and need to decide
      # our strategy here.
      <<~RUBY
        begin
          #{transformation}
        rescue NoMethodError => e
          raise_deserialization_error(
            #{prop.inspect},
            val,
            e,
          )
          val
        end
      RUBY
    else
      'val'
    end

    nil_handler = generate_nil_handler(
      prop: prop,
      serialized_form: hash_key,
      default: defaults[prop],
      nilable_type: T::Props::Utils.optional_prop?(rules),
      raise_on_nil_write: !!rules[:raise_on_nil_write],
    )

    <<~RUBY
      val = hash[#{hash_key.inspect}]
      #{ivar_name} = if val.nil?
        found -= 1 unless hash.key?(#{hash_key.inspect})
        #{nil_handler}
      else
        #{transformed_val}
      end
    RUBY
  end

  <<~RUBY
    def __t_props_generated_deserialize(hash)
      found = #{stored_props.size}
      #{parts.join("\n\n")}
      found
    end
  RUBY
end