Fix alias on dependent param bug

CHANGELOG.md

@@ -14,6 +14,7 @@
 * [#1776](https://github.com/ruby-grape/grape/pull/1776): Validate response returned by the exception handler - [@darren987469](https://github.com/darren987469).
 * [#1787](https://github.com/ruby-grape/grape/pull/1787): Add documented but not implemented ability to `.insert` a middleware in the stack - [@michaellennox](https://github.com/michaellennox).
 * [#1788](https://github.com/ruby-grape/grape/pull/1788): Fix route requirements bug - [@darren987469](https://github.com/darren987469), [@darrellnash](https://github.com/darrellnash).
+* [#1810](https://github.com/ruby-grape/grape/pull/1810): Fix support in `given` for aliased params - [@darren987469](https://github.com/darren987469).
 
 ### 1.1.0 (8/4/2018)
 

README.md

@@ -1175,6 +1175,18 @@ params do
 end
 ```
 
+You can set alias for parameter:
+
+```ruby
+params do
+  optional :category, as: :type
+  given type: ->(val) { val == 'foo' } do
+    requires :description
+  end
+end
+```
+
+Note: param in `given` should be the aliased one. In the example, it should be `type`, not `category`.
 
 ### Group Options
 

lib/grape/validations/params_scope.rb

@@ -121,6 +121,7 @@ def push_declared_params(attrs, **opts)
           if opts && opts[:as]
             @api.route_setting(:aliased_params, @api.route_setting(:aliased_params) || [])
             @api.route_setting(:aliased_params) << { attrs.first => opts[:as] }
+            attrs = [opts[:as]]
           end
 
           @declared_params.concat attrs

spec/grape/validations/params_scope_spec.rb

@@ -497,6 +497,34 @@ def initialize(value)
       expect(body.keys).to_not include('b')
     end
 
+    it 'allows aliasing of dependent on parameter' do
+      subject.params do
+        optional :a, as: :b
+        given b: ->(val) { val == 'x' } do
+          requires :c
+        end
+      end
+      subject.get('/') { declared(params) }
+
+      get '/', a: 'x'
+      expect(last_response.status).to eq 400
+      expect(last_response.body).to eq 'c is missing'
+
+      get '/', a: 'y'
+      expect(last_response.status).to eq 200
+    end
+
+    it 'raises an error if the dependent parameter is not the aliased one' do
+      expect do
+        subject.params do
+          optional :a, as: :b
+          given :a do
+            requires :c
+          end
+        end
+      end.to raise_error(Grape::Exceptions::UnknownParameter)
+    end
+
     it 'does not validate nested requires when given is false' do
       subject.params do
         requires :a, type: String, allow_blank: false, values: %w[x y z]