API only apps: Preserve request format for HTML requests too

- Earlier we were responding with JSON format for HTML requests in a API
  app.
- Now we will respond with HTML format for such requests in API apps.
- Also earlier we were not testing the API app's JSON requests
  properly. We were actually sending HTML requests. Now we send correct
  JSON requests. Also added more test coverage.
- Based on the discussion from this commit -
  https://github.com/rails/rails/commit/05d89410bf97d0778e78558db3c9fed275f8a614.

[Prathamesh Sonpatki, Jorge Bejar]

1 files changed, 12 insertions, 8 deletions

diff --git a/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb b/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb
index 51a471fb23..5f758d641a 100644
--- a/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb
+++ b/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb
@@ -67,18 +67,19 @@ module ActionDispatch
       log_error(request, wrapper)
 
       if request.get_header('action_dispatch.show_detailed_exceptions')
-        case @response_format
-        when :api
-          render_for_api_application(request, wrapper)
-        when :default
-          render_for_default_application(request, wrapper)
+        content_type = request.formats.first
+
+        if api_request?(content_type)
+          render_for_api_request(content_type, wrapper)
+        else
+          render_for_browser_request(request, wrapper)
         end
       else
         raise exception
       end
     end
 
-    def render_for_default_application(request, wrapper)
+    def render_for_browser_request(request, wrapper)
       template = create_template(request, wrapper)
       file = "rescues/#{wrapper.rescue_template}"
 
@@ -92,7 +93,7 @@ module ActionDispatch
       render(wrapper.status_code, body, format)
     end
 
-    def render_for_api_application(request, wrapper)
+    def render_for_api_request(content_type, wrapper)
       body = {
         status: wrapper.status_code,
         error:  Rack::Utils::HTTP_STATUS_CODES.fetch(
@@ -103,7 +104,6 @@ module ActionDispatch
         traces: wrapper.traces
       }
 
-      content_type = request.formats.first
       to_format = "to_#{content_type.to_sym}"
 
       if content_type && body.respond_to?(to_format)
@@ -181,5 +181,9 @@ module ActionDispatch
         ActionDispatch::Routing::RoutesInspector.new(@routes_app.routes.routes)
       end
     end
+
+    def api_request?(content_type)
+      @response_format == :api && !content_type.html?
+    end
   end
 end