Extended given to receive a Proc

CHANGELOG.md

@@ -8,8 +8,9 @@
 * [#1390](https://github.com/ruby-grape/grape/pull/1390): Allow inserting middleware at arbitrary points in the middleware stack - [@Rosa](https://github.com/Rosa).
 * [#1366](https://github.com/ruby-grape/grape/pull/1366): Store `message_key` on `Grape::Exceptions::Validation` - [@mkou](https://github.com/mkou).
 * [#1398](https://github.com/ruby-grape/grape/pull/1398): Added `rescue_from :grape_exceptions` - allow Grape to use the built-in `Grape::Exception` handing and use `rescue :all` behavior for everything else - [@mmclead](https://github.com/mmclead).
+* [#1443](https://github.com/ruby-grape/grape/pull/1443): Extended `given` to receive a `Proc` - [@glaucocustodio](https://github.com/glaucocustodio).
 * Your contribution here.
- 
+
 #### Fixes
 
 * [#1430](https://github.com/ruby-grape/grape/pull/1430): Fix for `declared(params)` inside `route_param` - [@Arkanain](https://github.com/Arkanain).

README.md

@@ -987,6 +987,19 @@ params do
 end
 ```
 
+In the example above Grape will use `blank?` to check whether the `shelf_id` param is present.
+
+Given also takes a `Proc` with custom code. Below, the param `description` is required only if the value of `category` is equal `foo`:
+
+```ruby
+params do
+  optional :category
+  given category: ->(val) { val == 'foo' } do
+    requires :description
+  end
+end
+```
+
 ### Built-in Validators
 
 #### `allow_blank`

lib/grape/dsl/parameters.rb

@@ -167,7 +167,8 @@ def all_or_none_of(*attrs)
       # @yield a parameter definition DSL
       def given(*attrs, &block)
         attrs.each do |attr|
-          raise Grape::Exceptions::UnknownParameter.new(attr) unless declared_param?(attr)
+          attr_ = attr.is_a?(Hash) ? attr.keys[0] : attr
+          raise Grape::Exceptions::UnknownParameter.new(attr_) unless declared_param?(attr_)
         end
         new_lateral_scope(dependent_on: attrs, &block)
       end

lib/grape/validations/params_scope.rb

@@ -39,7 +39,13 @@ def should_validate?(parameters)
                                        any_element_blank?(parameters))
 
         @dependent_on.each do |dependency|
-          return false if params(parameters).try(:[], dependency).blank?
+          if dependency.is_a?(Hash)
+            dependency_key = dependency.keys[0]
+            proc = dependency.values[0]
+            return false unless proc.call(params(parameters).try(:[], dependency_key))
+          elsif params(parameters).try(:[], dependency).blank?
+            return false
+          end
         end if @dependent_on
 
         return true if parent.nil?

spec/grape/validations/params_scope_spec.rb

@@ -405,4 +405,91 @@ def initialize(value)
       expect(JSON.parse(last_response.body)).to eq('bar' => { 'a' => 'true', 'c' => { 'b' => 'yes' } })
     end
   end
+
+  context 'when validations are dependent on a parameter with specific value' do
+    before do
+      subject.params do
+        optional :a
+        given a: ->(val) { val == 'x' } do
+          requires :b
+        end
+      end
+      subject.get('/test') { declared(params).to_json }
+    end
+
+    it 'applies the validations only if the parameter has the specific value' do
+      get '/test'
+      expect(last_response.status).to eq(200)
+
+      get '/test', a: 'x'
+      expect(last_response.status).to eq(400)
+      expect(last_response.body).to eq('b is missing')
+
+      get '/test', a: 'x', b: 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
+          given :c do
+          end
+        end
+      end.to raise_error(Grape::Exceptions::UnknownParameter)
+    end
+
+    it 'includes the parameter within #declared(params)' do
+      get '/test', a: true, b: true
+
+      expect(JSON.parse(last_response.body)).to eq('a' => 'true', 'b' => 'true')
+    end
+
+    it 'returns a sensible error message within a nested context' do
+      subject.params do
+        requires :bar, type: Hash do
+          optional :a
+          given a: ->(val) { val == 'x' } do
+            requires :b
+          end
+        end
+      end
+      subject.get('/nested') { 'worked' }
+
+      get '/nested', bar: { a: 'x' }
+      expect(last_response.status).to eq(400)
+      expect(last_response.body).to eq('bar[b] is missing')
+    end
+
+    it 'includes the nested parameter within #declared(params)' do
+      subject.params do
+        requires :bar, type: Hash do
+          optional :a
+          given a: ->(val) { val == 'x' } do
+            requires :b
+          end
+        end
+      end
+      subject.get('/nested') { declared(params).to_json }
+
+      get '/nested', bar: { a: 'x', b: 'yes' }
+      expect(JSON.parse(last_response.body)).to eq('bar' => { 'a' => 'x', 'b' => 'yes' })
+    end
+
+    it 'includes level 2 nested parameters outside the given within #declared(params)' do
+      subject.params do
+        requires :bar, type: Hash do
+          optional :a
+          given a: ->(val) { val == 'x' } do
+            requires :c, type: Hash do
+              requires :b
+            end
+          end
+        end
+      end
+      subject.get('/nested') { declared(params).to_json }
+
+      get '/nested', bar: { a: 'x', c: { b: 'yes' } }
+      expect(JSON.parse(last_response.body)).to eq('bar' => { 'a' => 'x', 'c' => { 'b' => 'yes' } })
+    end
+  end
 end