Use T::Utils.unwrap_nilable for scalar coerce_input return types

[KaanOzkan]

Motivation

type_for was stripping the T.nilable(...) wrapper from a custom scalar's coerce_input return type by formatting the runtime type to a string and matching a regex. Operating on the runtime type tree is both simpler and ~8x faster on the common T.nilable(SimpleType) case (measured: 15.3ms vs 1.8ms across 1000 calls).

Output is identical for every input the spec covers, including the new nilable-scalar case added in #2618.

Implementation

Use T::Utils.unwrap_nilable || return_type instead. unwrap_nilable returns nil if the type isn't nilable.

Tests

[paracycle]

I hadn't even realized that return_type was already a runtime type. This makes a lot of sense!

[amomchilov]

@paracycle There's actually several places where we to_s a runtime type, only to later try to regex our way into figuring out things back out about it.

e.g.

tapioca/lib/tapioca/dsl/helpers/active_model_type_helper.rb

Lines 11 to 22 in ab86175

	#: (untyped type_value) -> String
	def type_for(type_value)
	return "T.untyped" if Runtime::GenericTypeRegistry.generic_type_instance?(type_value)
	type = lookup_tapioca_type(type_value) ||
	lookup_return_type_of_method(type_value, :deserialize) ||
	lookup_return_type_of_method(type_value, :cast) ||
	lookup_return_type_of_method(type_value, :cast_value) ||
	lookup_arg_type_of_method(type_value, :serialize) ||
	T.untyped
	type.to_s
	end

tapioca/lib/tapioca/dsl/compilers/active_model_attributes.rb

Lines 123 to 124 in ab86175

	type = Helpers::ActiveModelTypeHelper.type_for(attribute_type_value)
	type = as_nilable_type(type) if Helpers::ActiveModelTypeHelper.assume_nilable?(attribute_type_value)

I considered changing it, but the repo deals with types as strings a fair bit. I think it would more clear (and generally faster) to operate on type values, and stringify them later.

What do you think?

[paracycle]

What do you think?

Overall, this is what I think: #2489

If we can move to our own type builder syntax, then we can also start generating RBS syntax if we wanted to.