dry-rb/chat - Gitter

ojab

@ojab

Jun 05 2018 15:26

type = Dry::Types['params.time'].constrained({}).optional
type[Dry::Types::Undefined]
# => Undefined violates constraints (Undefined must be an instance of Time failed) (Dry::Types::ConstraintError)

unconstrained type works fine, is it expected behaviour?

type[nil] doesn't raise, btw

Nikita Shilnikov

@flash-gordon

Jun 05 2018 15:57

why do you pass Undefined to optional?

optional has no default value, it's just strict.nil | whatever

ojab

@ojab

Jun 05 2018 16:03

I'm parsing stuff in constructor and I want to provide a value that will pass .optional and set default value, if exist. So AFAIU if I'll pass nil there will not be default value.

*default value in dry-struct that is used on upper level

ojab

@ojab

Jun 05 2018 16:30

and looks like my issue is a result of messing with dry-struct constructor

ojab

@ojab

Jun 05 2018 16:51

kinda reduced testcase:

type = Dry::Types['params.time'].constrained(
  gteq: ::Time.parse('1753-01-01 12:00:00')
)
type = type.constructor do |input|
  input.respond_to?(:to_time) ? input.to_time : input
end

TYPE = type.optional.meta(omittable: true)

User = Dry.Struct do
  attribute :time, type
end

p User.new(time: nil)
# => [User.new] nil (NilClass) has invalid type for :time violates constraints (nil must be an instance of Time failed) (Dry::Struct::Error)

ouch, passing type instead of TYPE, wrong reduction

ojab

@ojab

Jun 05 2018 17:30

another question then:

struct = Dry.Struct do
  attribute :time, Dry::Types['string']
end

struct = struct.constructor { |input| input }

struct.optional
# => undefined method `optional' for #<Dry::Struct::Constructor type=#<Class:0x000000000175bf10>> (NoMethodError)

dry-s should quack as dry-t, so this should work in theory?

ojab

@ojab

Jun 05 2018 17:38

and why coercion constructor runs before custom one?

hash = Dry::Types['hash'].constructor { |input| { x: 1 } }
coercible = Dry::Types['coercible.hash'].constructor { |input| { x: 1 } }

p hash['foo'] # => { x: 1 }
p coercible['foo'] # => can't convert String into Hash (TypeError)

Nikita Shilnikov

@flash-gordon

Jun 05 2018 17:47

and why not? It's ordinary function composition

we'll likely add option for alternative composition though before 1.0 is out

ojab

@ojab

Jun 05 2018 17:48

yeah, but I'm expecting that latter constructors will run before existing ones

hash = Dry::Types['hash'].constructor { |input| { x: 1 } }
                         .constructor { |input| { y: 2 } }
p hash['foo'] # => { y: 2 }

hmm, so I will receive input from existing constructors

Nikita Shilnikov

@flash-gordon

Jun 05 2018 17:51

I think people may have different opinions on the matter, as in, function composition is usually defined as f . g = \x -> f(g(x)) (read "f after g")

but there's nothing wrong with the opposite order

it's just we need to come up with some API

will add a flag probably