allow headers to be set in the configuration of rswag-api

README.md

@@ -44,9 +44,9 @@ Once you have an API that can describe itself in Swagger, you've opened the trea
     ```ruby
     rails g rswag:install
     ```
-    
+
     Or run the install generators for each package separately if you installed Rswag as separate gems, as indicated above:
-    
+
     ```ruby
     rails g rswag:api:install rswag:ui:install
     RAILS_ENV=test rails g rswag:specs:install
@@ -466,6 +466,19 @@ end
 
 Note how the filter is passed the rack env for the current request. This provides a lot of flexibilty. For example, you can assign the "host" property (as shown) or you could inspect session information or an Authoriation header and remove operations based on user permissions.
 
+### Custom Headers for Swagger Files ###
+
+You can specify custom headers for serving your generated Swagger JSON. For example you may want to force a specific charset for the 'Content-Type' header. You can configure a hash of headers to be sent with the request:
+
+```ruby
+Rswag::Api.configure do |c|
+  ...
+  
+  c.swagger_headers = { 'Content-Type' => 'application/json; charset=UTF-8' }
+end
+```
+
+
 ### Enable Swagger Endpoints for swagger-ui ###
 
 You can update the _rswag-ui.rb_ initializer, installed with rswag-ui, to specify which Swagger endpoints should be available to power the documentation UI. If you're using rswag-api, these should correspond to the Swagger endpoints it exposes. When the UI is rendered, you'll see these listed in a drop-down to the top right of the page:

rswag-api/lib/rswag/api/configuration.rb

@@ -1,7 +1,7 @@
 module Rswag
   module Api
     class Configuration
-      attr_accessor :swagger_root, :swagger_filter
+      attr_accessor :swagger_root, :swagger_filter, :swagger_headers
 
       def resolve_swagger_root(env)
         path_params = env['action_dispatch.request.path_parameters'] || {}

rswag-api/lib/rswag/api/middleware.rb

@@ -2,7 +2,7 @@ require 'json'
 
 module Rswag
   module Api
-    class Middleware 
+    class Middleware
 
       def initialize(app, config)
         @app = app
@@ -16,14 +16,15 @@ module Rswag
         if env['REQUEST_METHOD'] == 'GET' && File.file?(filename)
           swagger = load_json(filename)
           @config.swagger_filter.call(swagger, env) unless @config.swagger_filter.nil?
+          headers = { 'Content-Type' => 'application/json' }.merge(@config.swagger_headers || {})
 
           return [
             '200',
-            { 'Content-Type' => 'application/json' },
+            headers,
             [ JSON.dump(swagger) ]
           ]
         end
-          
+
         return @app.call(env)
       end
 

rswag-api/spec/rswag/api/middleware_spec.rb

@@ -37,6 +37,42 @@ module Rswag
           end
         end
 
+        context 'when swagger_headers is configured' do
+          let(:env) { env_defaults.merge('PATH_INFO' => 'v1/swagger.json') }
+
+          context 'replacing the default content type header' do
+            before do
+              config.swagger_headers = { 'Content-Type' => 'application/json; charset=UTF-8' }
+            end
+            it 'returns a 200 status' do
+              expect(response.length).to eql(3)
+              expect(response.first).to eql('200')
+            end
+
+            it 'applies the headers to the response' do
+              expect(response[1]).to include( 'Content-Type' => 'application/json; charset=UTF-8')
+            end
+          end
+
+          context 'adding an additional header' do
+            before do
+              config.swagger_headers = { 'Access-Control-Allow-Origin' => '*' }
+            end
+            it 'returns a 200 status' do
+              expect(response.length).to eql(3)
+              expect(response.first).to eql('200')
+            end
+
+            it 'applies the headers to the response' do
+              expect(response[1]).to include( 'Access-Control-Allow-Origin' => '*')
+            end
+
+            it 'keeps the default header' do
+              expect(response[1]).to include( 'Content-Type' => 'application/json')
+            end
+          end
+        end
+
         context "given a path that doesn't map to any swagger file" do
           let(:env) { env_defaults.merge('PATH_INFO' => 'foobar.json') }
           before do