Fix: be defensive with nil types in the API documentation.

CHANGELOG.md

@@ -1,6 +1,7 @@
 ### 0.10.1 (Next)
 
 * [#227](https://github.com/tim-vandecasteele/grape-swagger/issues/227): Fix: nested routes under prefix not documented - [@dblock](https://github.com/dblock).
+* [#226](https://github.com/tim-vandecasteele/grape-swagger/issues/226): Fix: be defensive with nil exposure types - [@dblock](https://github.com/dblock).
 * Your contribution here.
 
 ### 0.10.0 (March 10, 2015)

lib/grape-swagger.rb

@@ -332,8 +332,9 @@ def parse_entity_models(models)
 
                   type = if p[:type]
                            p.delete(:type)
-                         elsif (entity = model.exposures[property_name][:using])
-                           parse_entity_name(entity)
+                         else
+                           exposure = model.exposures[property_name]
+                           parse_entity_name(exposure[:using]) if exposure
                          end
 
                   if p.delete(:is_array)

spec/api_with_nil_types.rb

@@ -0,0 +1,50 @@
+require 'spec_helper'
+
+describe 'API with minimally documented models' do
+  def app
+    entity_klass = Class.new do
+      def self.exposures
+        {}
+      end
+
+      def self.documentation
+        {
+          bar: { type: String },
+          foo: {}
+        }
+      end
+
+      def self.entity_name
+        'Foo'
+      end
+    end
+
+    Class.new(Grape::API) do
+      format :json
+
+      get :foo do
+      end
+
+      add_swagger_documentation \
+        format: :json,
+        models: [Class.new(entity_klass)]
+    end
+  end
+
+  subject do
+    get '/swagger_doc/foo'
+    JSON.parse(last_response.body)['models']
+  end
+
+  it 'returns model' do
+    expect(subject).to eq(
+      'Foo' => {
+        'id' => 'Foo',
+        'properties' => {
+          'bar' => { 'type' => 'string' },
+          'foo' => { '$ref' => nil }
+        }
+      }
+    )
+  end
+end