Allow empty model definitions for Swagger 2.0

.rspec

@@ -1,3 +1,4 @@
 --color
 --profile
 --format documentation
+--require 'spec_helper'

lib/grape-swagger/doc_methods/build_model_definition.rb

@@ -22,7 +22,7 @@ def parse_params_from_model(parsed_response, model, model_name)
             }
           else
             properties, required = parsed_response
-            unless properties&.any?
+            if properties.nil?
               raise GrapeSwagger::Errors::SwaggerSpec,
                     "Empty model #{model_name}, swagger 2.0 doesn't support empty definitions."
             end

spec/issues/539_array_post_body_spec.rb

@@ -74,7 +74,8 @@ class ArrayOfElements < Grape::Entity
           'id' => { 'type' => 'string' },
           'description' => { 'type' => 'string' },
           'role' => { 'type' => 'string' }
-        }
+        },
+        'required' => %w[id description role]
       }
     )
   end

spec/issues/962_polymorphic_entity_with_custom_documentation_spec.rb

@@ -0,0 +1,110 @@
+# frozen_string_literal: true
+
+describe '#962 polymorphic entity with custom documentation' do
+  let(:app) do
+    Class.new(Grape::API) do
+      namespace :issue_962 do
+        module Issue962
+          class EmptyEntity < Grape::Entity
+          end
+
+          class EntityWithHiddenProperty < Grape::Entity
+            expose :hidden_prop, documentation: { hidden: true, desc: 'This property is not exposed.' }
+          end
+
+          class EntityWithNestedEmptyEntity < Grape::Entity
+            expose :array_of_empty_entities,
+                   as: :empty_items,
+                   using: Issue962::EmptyEntity,
+                   documentation: {
+                     is_array: true,
+                     desc: 'This is a nested empty entity.'
+                   }
+            expose :array_of_hidden_entities,
+                   as: :hidden_items,
+                   using: Issue962::EntityWithHiddenProperty,
+                   documentation: {
+                     is_array: true,
+                     desc: 'This is a nested entity with hidden props'
+                   }
+          end
+        end
+
+        desc 'Get a report',
+             success: Issue962::EntityWithNestedEmptyEntity
+        get '/' do
+          present({ foo: [] }, with: Issue962::EntityWithNestedEmptyEntity)
+        end
+      end
+
+      add_swagger_documentation format: :json
+    end
+  end
+
+  subject do
+    get '/swagger_doc'
+    JSON.parse(last_response.body)
+  end
+
+  let(:definitions) { subject['definitions'] }
+  let(:entity_definition) { definitions['Issue962_EntityWithNestedEmptyEntity'] }
+  let(:empty_items_property) { entity_definition['properties']['empty_items'] }
+  let(:hidden_items_property) { entity_definition['properties']['hidden_items'] }
+  let(:empty_entity_definition) { definitions['Issue962_EmptyEntity'] }
+  let(:hidden_entity_definition) { definitions['Issue962_EntityWithHiddenProperty'] }
+
+  specify 'should generate swagger documentation without error' do
+    expect { subject }.not_to raise_error
+  end
+
+  specify do
+    expect(definitions.keys).to include(
+      'Issue962_EntityWithNestedEmptyEntity',
+      'Issue962_EntityWithHiddenProperty',
+      'Issue962_EmptyEntity'
+    )
+  end
+
+  specify do
+    expect(empty_items_property).to eql({
+      'type' => 'array',
+      'description' => 'This is a nested empty entity.',
+      'items' => {
+        '$ref' => '#/definitions/Issue962_EmptyEntity'
+      }
+    })
+  end
+
+  specify do
+    expect(hidden_items_property).to eql({
+      'type' => 'array',
+      'description' => 'This is a nested entity with hidden props',
+      'items' => {
+        '$ref' => '#/definitions/Issue962_EntityWithHiddenProperty'
+      }
+    })
+  end
+
+  specify do
+    expect(empty_entity_definition).to eql({
+      'type' => 'object',
+      'properties' => {}
+    })
+  end
+
+  specify do
+    expect(hidden_entity_definition).to eql({
+      'type' => 'object',
+      'properties' => {},
+      'required' => ['hidden_prop']
+    })
+  end
+
+  let(:response_schema) { subject['paths']['/issue_962']['get']['responses']['200']['schema'] }
+
+  specify do
+    expect(response_schema).to eql({
+      '$ref' => '#/definitions/Issue962_EntityWithNestedEmptyEntity'
+    })
+  end
+end

spec/swagger_v2/errors_spec.rb

@@ -34,8 +34,8 @@
       end
     end
 
-    it 'should raise SwaggerSpec exception' do
-      expect { get '/v3/swagger_doc' }.to raise_error(GrapeSwagger::Errors::SwaggerSpec, "Empty model EmptyClass, swagger 2.0 doesn't support empty definitions.")
+    it 'should not raise SwaggerSpec exception' do
+      expect { get '/v3/swagger_doc' }.not_to raise_error(GrapeSwagger::Errors::SwaggerSpec)
     end
   end
 

spec/swagger_v2/reference_entity_spec.rb

@@ -90,7 +90,9 @@ def app
 
       expect(subject['definitions'].keys).to include 'SomethingCustom'
       expect(subject['definitions']['SomethingCustom']).to eq(
-        'type' => 'object', 'properties' => { 'text' => { 'type' => 'string', 'description' => 'Content of something.' } }
+        'type' => 'object',
+        'properties' => { 'text' => { 'type' => 'string', 'description' => 'Content of something.' } },
+        'required' => ['text']
       )
 
       expect(subject['definitions'].keys).to include 'KindCustom'
@@ -103,6 +105,7 @@ def app
             'description' => 'Something interesting.'
           }
         },
+        'required' => %w[title something],
         'description' => 'KindCustom model'
       )
     end
@@ -122,6 +125,7 @@ def app
           'title' => { 'type' => 'string', 'description' => 'Title of the parent.' },
           'child' => { 'type' => 'string', 'description' => 'Child property.' }
         },
+        'required' => %w[title child],
         'description' => 'MyAPI::Child model'
       )
     end