Parameter dependecy using `given` does not work with nested arrays and custom block

[nicooga]

What's happening

Given I declared some rules to be dependent on other param using given parameter: -> v { v } and I did it inside a nested array param, it raises error.

Expected behavior

It should apply the rules.

Extended Explanation

Given this params:

params do
  optional :comments, type: Array do
    optional :_destroy, coerce: Boolean
    given _destroy: -> v { !v } do
      requires :name
    end
  end
end

put('/asdf') do
  declared(params)
end

When I call the controller with this params:

{"comments": [{ "_destroy": true}]}

It fails with:

TypeError (no implicit conversion of Symbol into Integer):
  
activesupport (5.0.1) lib/active_support/core_ext/object/try.rb:17:in `[]'
activesupport (5.0.1) lib/active_support/core_ext/object/try.rb:17:in `public_send'
activesupport (5.0.1) lib/active_support/core_ext/object/try.rb:17:in `try!'
activesupport (5.0.1) lib/active_support/core_ext/object/try.rb:6:in `try'
grape (0.19.1) lib/grape/validations/params_scope.rb:49:in `block in should_validate?'

This is the source from grape where it fails:

          if dependency.is_a?(hash)
            dependency_key = dependency.keys[0]
            proc = dependency.values[0]
            require 'pry'
            binding.pry
            return false unless proc.call(params(parameters).try(:[], dependency_key))

I have put a binding.pry here on the source to see what's happening.

[1] pry(#<Grape::Validations::ParamsScope>)> params(parameters)
=> [{"_destroy"=>true}]
[3] pry(#<Grape::Validations::ParamsScope>)> dependency_key
=> :_destroy

The validations are being run over the entire array instead of over each element of it. It basically runs [{"_destroy"=>true}][:_destroy] which raises the TypeError (no implicit conversion of Symbol into Integer) error.

[dblock]

Closing via #1625