How to remove empty Strings from `params` Hash

Support dry-validation
1

How do I use dry-validation or dry-schema to remove empty Strings from a HTTP params Hash entirely? Instead of coercing them to nil, I would prefer to just omit them entirely, so that the params Hash is much smaller before sending it to a backend Sidekiq worker.

2

I think you can use this dry-rb - dry-schema v1.10 - Processor steps

If what you want to do is remove keys with empty values the example is doing exactly that.

3

I guess I could call .reject { |k,v| v.empty? }.

schema = Dry::Schema.Params do
  required(:name).value(:string)
  optional(:age).value(:integer)

  before(:value_coercer) do |result|
    result.to_h.reject { |k,v| v.empty? }
  end
end

schema.call(name: 'Jane', age: '')
# => #<Dry::Schema::Result{:name=>"Jane"} errors={} path=[]>

Is this the ideal way of filtering out empty Strings?

4

Well, I also dont know if there is a better way, I have used this feature in the past but the experimental warning on the docs made me leave a TODO on the code to investigate this a bit better.

5

How would I “DRY” up that before(:value_coercer) code if I needed to add it to multiple Dry::Schemas or Dry::Validation:Contracts? I suppose I could store the block as a constant and pass it in as &BLOCK. Since the actual schema block is evaluated within a Dry::Schema::DSL instance, I cannot call include to include Mixin modules that have self.included hooks. Would I define a Mixin module with a self.extended method and extend the Mixin module inside the Dry::Schema?

6

I dont know the proper way of extracting that.
This really ugly (and probably wrong) monkey patch on Dry::Schema::ProcessorSteps apparently works but I’m positive it will break other stuff

class Dry::Schema::ProcessorSteps
  reject_empty = [proc {|r| r.to_h.reject { |k,v| v.empty? }}]
  option :before_steps, default: -> { {value_coercer: reject_empty} }
end

schema = Dry::Schema.Params do
  required(:name).value(:string)
  optional(:age).value(:integer)
end

p schema.call(name: 'Jane', age: '')
#<Dry::Schema::Result{:name=>"Jane", :age=>""} errors={:age=>["must be an integer"]} path=[]>