Reusable schema fragments

Support dry-validation
1

One feature I’ve notice dry-validation (or rather dry-schema) lacks is the ability to compose a schema from previously defined chunks.
In plain-old Ruby, common functionality can be extracted into modules and added to other objects using include, extend, or prepend. In a Rails app, Concerns build upon that paradigm.

To give an example of the problem, one of the applications I’m working on has 30 or so instances of this:

params do
  optional(:page).value(:integer, gteq?: 1)
  optional(:per_page).value(:integer, included_in?: [10, 25, 50])
  # Other parameters ...
end

Ideally, this would be pulled out into a Pagination fragment or similar, and then be reused across all of the contracts.
ie.

params do
  fragment(:pagination)
  # Other parameters ...
end

I’ve hacked out something that does work, the ergonomics are rather suboptimal:

module Pagination
  def self.extended(object)
    super(object)
    object.instance_eval do
      optional(:page).value(:integer, gteq?: 1)
      optional(:per_page).value(:integer, included_in?: [10, 25, 50])
    end
  end
end

Then, in the contract:

params do
  extend Pagination
  # Other parameters ...
end

It would be nice for to have a cleaner DSL available to do this since feature extraction plays a major part in DRYing up a codebase. :wink:

2

We are working on exactly this and sooner or later merging schemas will be available. Stay tuned :slight_smile: