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.

Constant Summary collapse

CAN_USE_SYMBOL_NAME = 
T.let(RUBY_VERSION >= "3.3.0", T::Boolean)

Class Method Summary collapse

Methods included from Sig

sig

Methods included from T::Private::Methods::SingletonMethodHooks

#singleton_method_added

Methods included from T::Private::Methods::MethodHooks

#method_added

Class Method Details

.generate(props, defaults) ⇒ Object 



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# File 'lib/types/props/private/deserializer_generator.rb', line 33

def self.generate(props, defaults)
  parts = props.filter_map do |prop, rules|
    next if rules[:dont_store]

    # 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?(CAN_USE_SYMBOL_NAME ? prop.name : prop.to_s)

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

    key = rules.fetch(:accessor_key)
    ivar_name = CAN_USE_SYMBOL_NAME ? key.name : key.to_s
    raise unless ivar_name.start_with?('@') && T::Props::Decorator::SAFE_ACCESSOR_KEY_NAME.match?(ivar_name)

    transformation = SerdeTransform.generate(
      T::Utils::Nilable.get_underlying_type_object(rules.fetch(:type_object)),
      SerdeTransform::Mode::DESERIALIZE,
      'val'
    )
    transformed_val = transformation || 'val'

    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],
    )

    # The `.freeze` on the `hash.key?` argument matters: when this source
    # is eval'd lazily (without a frozen-string-literal prefix, unlike
    # `eagerly_define_lazy_methods!`), a bare literal here would allocate
    # a new String on every call for each nil/missing prop. `"str".freeze`
    # compiles to a no-allocation VM instruction (opt_str_freeze). The
    # `hash[...]` read doesn't need it because of opt_aref_with.
    <<~RUBY
      val = hash[#{hash_key.inspect}]
      #{ivar_name} = if val.nil?
        found -= 1 unless hash.key?(#{hash_key.inspect}.freeze)
        #{nil_handler}
      else
        #{transformed_val}
      end
    RUBY
  end

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