Added functionality to given to allow it to pass in multiple arguments which will create nested scopes.

Author: Ozer Chagatai

CHANGELOG.md

@@ -5,6 +5,7 @@
 
 * [#1227](https://github.com/ruby-grape/grape/pull/1227): Store `message_key` on Grape::Exceptions::Validation - [@stjhimy](https://github.com/sthimy).
 * [#1232](https://github.com/ruby-grape/grape/pull/1232): Helpers are now available inside `rescue_from` - [@namusyaka](https://github.com/namusyaka).
+* [#1237](https://github.com/ruby-grape/grape/pull/1237): Allow multiple parameters in `given`, which behaves as if the scopes were nested in the inputted order - [@ochagata](https://github.com/ochagata).
 * Your contribution here.
 
 #### Fixes

lib/grape/dsl/parameters.rb

@@ -165,9 +165,11 @@ def all_or_none_of(*attrs)
       # @raise Grape::Exceptions::UnknownParameter if `attr` has not been
       #   defined in this scope yet
       # @yield a parameter definition DSL
-      def given(attr, &block)
-        fail Grape::Exceptions::UnknownParameter.new(attr) unless declared_param?(attr)
-        new_lateral_scope(dependent_on: attr, &block)
+      def given(*attrs, &block)
+        attrs.each do |attr|
+          fail Grape::Exceptions::UnknownParameter.new(attr) unless declared_param?(attr)
+        end
+        new_lateral_scope(dependent_on: attrs, &block)
       end
 
       # Test for whether a certain parameter has been defined in this params

lib/grape/validations/params_scope.rb

@@ -36,7 +36,9 @@ def initialize(opts, &block)
       #   validated
       def should_validate?(parameters)
         return false if @optional && params(parameters).respond_to?(:all?) && params(parameters).all?(&:blank?)
-        return false if @dependent_on && params(parameters).try(:[], @dependent_on).blank?
+        @dependent_on.each do |dependency|
+          return false if params(parameters).try(:[], dependency).blank?
+        end if @dependent_on
         return true if parent.nil?
         parent.should_validate?(parameters)
       end

spec/grape/validations/params_scope_spec.rb

@@ -298,6 +298,32 @@ def initialize(value)
       expect(last_response.status).to eq(200)
     end
 
+    it 'applies the validations of multiple parameters' do
+      subject.params do
+        optional :a, :b
+        given :a, :b do
+          requires :c
+        end
+      end
+      subject.get('/multiple') { declared(params).to_json }
+
+      get '/multiple'
+      expect(last_response.status).to eq(200)
+
+      get '/multiple', a: true
+      expect(last_response.status).to eq(200)
+
+      get '/multiple', b: true
+      expect(last_response.status).to eq(200)
+
+      get '/multiple', a: true, b: true
+      expect(last_response.status).to eq(400)
+      expect(last_response.body).to eq('c is missing')
+
+      get '/multiple', a: true, b: true, c: true
+      expect(last_response.status).to eq(200)
+    end
+
     it 'raises an error if the dependent parameter was never specified' do
       expect do
         subject.params do