Params namespace disapearing about dry-types HOT 9 OPEN

It's not a bug, it's just how ruby works. You'll get the same results with something like

GemTypes = Dry.Types()
GemTypes::Params::Integer # => returns type, ok

module Types
  include GemTypes
  # here Params::Integer is still available 
  # because it's inherited from GemTypes

  module Params # this shadows Params of GemTypes
    # now Types::Params references to another module, not one defined in GemTypes
  end
end

There are a bunch of workarounds you can apply. Simplest:

# don't use inheritence
Types = Dry.Types() 
# instead, work with the module created by dry-types directly
module Types
  module Params
    PageSize = Types::Params::Integer
  end
end

Another option is avoiding shadowing:

module Types
  include Dry.Types()

  Params::PageSize = Params::Integer
end

or

module Types
  types = Dry::Types().tap { include _1 }

  module types::Params
    PageSize = Types::Params::Integer
  end
end

or

module Types
  include Dry::Types()

  module ancestors[1]::Params
    PageSize = Types::Params::Integer
  end
end

from dry-types.

Wait, this is counter-intuitive. I would expect this to work. Given that Types::Params works, why re-opening the module does not?

from dry-types.

@solnic because it's not reopening the module but creating a new one. We can't control it. We could change our examples to Types = Dry::Types(), it'll help somewhat.

from dry-types.

@flash-gordon do you know if it's possible to define regular modules for Param JSON etc.? It feels like we're violating POLS here.

from dry-types.

@solnic I'm pretty sure you can subscribe to the included hook and define modules there. This would be surprising to me OTOH because it has nothing to do with dry-types rather how ruby operates itself. I've once heard of a framework that tries to improve ruby, not sure they really pulled this off. I suggest updating docs to Types = Dry.Types() and call it a day. Same effect, no magic.
Keep in mind, lexical scoping in ruby is far from being self-evident. For instance, you can't make it work with either approach:

RSpec.describe 'foo' do
  include Dry.Types

  specify do
    Params # boom, no params!
  end
end

Oh! I have another suggestion actually! We can detect when the user overrides exported modules and give a proper warning. WDYT? This way we won't bend ruby (with unforeseeable consequences) and provide robust UX.

from dry-types.

I've been bitten by this before too, ended up scratching my head for a bit and then went for one of the workarounds.

I think if we follow this recommendation of @flash-gordon's:

I suggest updating docs to Types = Dry.Types() and call it a day. Same effect, no magic.

We'd effectively solve this issue for 99.9% of our users.

Is this the one you're suggesting, @flash-gordon?

# don't use inheritence
Types = Dry.Types() 
# instead, work with the module created by dry-types directly
module Types
  module Params
    PageSize = Types::Params::Integer
  end
end

That said, this suggestion does sound good too, if we're able to do it :)

We can detect when the user overrides exported modules and give a proper warning. WDYT?

from dry-types.

Is this the one you're suggesting, @flash-gordon?

Yep.

I think applying both improvements is a good way of solving this.

from dry-types.

Yeah let's just fix it via docs and:

We can detect when the user overrides exported modules and give a proper warning. WDYT?

sounds good to me too.

from dry-types.

hm, it's not possible to detect if there was a constant definition, not without tracepoint API at least, that'd be overkill FWIW https://bugs.ruby-lang.org/issues/17881

from dry-types.