[#1719] Fix missing headers before error! call

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 * Your contribution here.
 * [#1864](https://github.com/ruby-grape/grape/pull/1864): Adds `finally` on the API - [@myxoh](https://github.com/myxoh).
+* [#1869](https://github.com/ruby-grape/grape/pull/1869): Fix issue with empty headers after `error!` method call - [@anaumov](https://github.com/anaumov).
 
 #### Fixes
 

lib/grape/dsl/inside_route.rb

@@ -134,8 +134,9 @@ def version
       #
       # @param message [String] The message to display.
       # @param status [Integer] the HTTP Status Code. Defaults to default_error_status, 500 if not set.
-      def error!(message, status = nil, headers = nil)
+      def error!(message, status = nil, additional_headers = nil)
         self.status(status || namespace_inheritable(:default_error_status))
+        headers = additional_headers.present? ? header.merge(additional_headers) : header
         throw :error, message: message, status: self.status, headers: headers
       end
 

spec/grape/endpoint_spec.rb

@@ -1089,6 +1089,17 @@ def app
       expect(last_response.headers['X-Custom']).to eq('value')
     end
 
+    it 'returns headers set before error!' do
+      subject.get '/hey' do
+        header 'X-Test', 'sample'
+        error!({ 'dude' => 'rad' }, 403)
+      end
+
+      get '/hey.json'
+      expect(last_response.status).to eq(403)
+      expect(last_response.headers['X-Test']).to eq('sample')
+    end
+
     it 'sets the status code for the endpoint' do
       memoized_endpoint = nil