Allow Proc for enum values in documentation (#77)

* Allow Proc for enum values in documentation

Enables the use of a Proc for the `values` option within
Grape::Entity documentation. This allows for dynamic generation of
enum values based on runtime logic when generating Swagger
specifications.

For example, this is useful when you want to specify a model's enum
for the `values` option and need to lazy-load the model, like this:

```ruby
expose :some, documentation: { values: -> { Model.some_enum.keys } }
```

This provides consistency, as Proc is also allowed for the `values`
option in request parameters:
https://github.com/ruby-grape/grape-swagger/blob/3e842a138b0f5edd2538d9da4aa23276e63e5d5c/lib/grape-swagger/doc_methods/parse_params.rb#L179-L180

* Set enum only if the return value of Proc is an Array

Author: krororo

.rubocop_todo.yml

@@ -100,7 +100,7 @@ RSpec/DescribeClass:
 # Offense count: 4
 # Configuration parameters: CountAsOne.
 RSpec/ExampleLength:
-  Max: 186
+  Max: 187
 
 # Offense count: 24
 RSpec/LeakyConstantDeclaration:

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 * Your contribution here.
 * [#76](https://github.com/ruby-grape/grape-swagger-entity/pull/76): Update ci matrix and gemfile for multi-version grape testing - [@numbata](https://github.com/numbata).
+* [#77](https://github.com/ruby-grape/grape-swagger-entity/pull/77): Allow proc for enum values in documentation - [@krororo](https://github.com/krororo).
 
 #### Fixes
 

lib/grape-swagger/entity/attribute_parser.rb

@@ -95,9 +95,9 @@ def document_data_type(documentation, data_type)
 
         type[:format] = documentation[:format] if documentation.key?(:format)
 
-        if (values = documentation[:values]) && values.is_a?(Array)
-          type[:enum] = values
-        end
+        values = documentation[:values]
+        values = values.call if values.is_a?(Proc)
+        type[:enum] = values if values.is_a?(Array)
 
         type
       end

spec/grape-swagger/entities/response_model_spec.rb

@@ -100,6 +100,7 @@ class Values < Grape::Entity
           expose :guid, documentation: { desc: 'Some values', values: %w[a b c], default: 'c' }
           expose :uuid, documentation: { desc: 'customer uuid', type: String, format: 'own',
                                          example: 'e3008fba-d53d-4bcc-a6ae-adc56dff8020' }
+          expose :color, documentation: { desc: 'Color', type: String, values: -> { %w[red blue] } }
         end
 
         class Kind < Grape::Entity
@@ -231,7 +232,8 @@ def app
       'properties' => {
         'guid' => { 'type' => 'string', 'enum' => %w[a b c], 'default' => 'c', 'description' => 'Some values' },
         'uuid' => { 'type' => 'string', 'format' => 'own', 'description' => 'customer uuid',
-                    'example' => 'e3008fba-d53d-4bcc-a6ae-adc56dff8020' }
+                    'example' => 'e3008fba-d53d-4bcc-a6ae-adc56dff8020' },
+        'color' => { 'type' => 'string', 'enum' => %w[red blue], 'description' => 'Color' }
       }
     )
     expect(subject['TheseApi_Entities_Kind']).to eql(