Introduce Kemal::InitHandler to initialize HTTP::Server::Context with defaults

src/kemal/common_exception_handler.cr

@@ -7,12 +7,10 @@ module Kemal
       begin
         call_next(context)
       rescue Kemal::Exceptions::RouteNotFound
-        context.response.content_type = "text/html"
         call_exception_with_status_code(context, 404)
       rescue Kemal::Exceptions::CustomException
         call_exception_with_status_code(context, context.response.status_code)
       rescue ex : Exception
-        context.response.content_type = "text/html"
         Kemal.config.logger.write("Exception: #{ex.inspect_with_backtrace}\n")
         return call_exception_with_status_code(context, 500) if Kemal.config.error_handlers.has_key?(500)
         verbosity = Kemal.config.env == "production" ? false : true

src/kemal/config.cr

@@ -58,33 +58,38 @@ module Kemal
       ERROR_HANDLERS[status_code] = ->(context : HTTP::Server::Context) { handler.call(context).to_s }
     end
 
+    def extra_options(&@extra_options : OptionParser ->)
+    end
+
     def setup
+      setup_init_handler
       setup_log_handler
       setup_error_handler
       setup_static_file_handler
     end
 
-    def setup_log_handler
+    private def setup_init_handler
+      HANDLERS.insert(0, Kemal::InitHandler::INSTANCE)
+    end
+
+    private def setup_log_handler
       @logger ||= if @logging
                     Kemal::CommonLogHandler.new
                   else
                     Kemal::NullLogHandler.new
                   end
-      HANDLERS.insert(0, @logger.not_nil!)
-    end
-
-    def extra_options(&@extra_options : OptionParser ->)
+      HANDLERS.insert(1, @logger.not_nil!)
     end
 
     private def setup_error_handler
       if @always_rescue
         @error_handler ||= Kemal::CommonExceptionHandler.new
-        HANDLERS.insert(1, @error_handler.not_nil!)
+        HANDLERS.insert(2, @error_handler.not_nil!)
       end
     end
 
     private def setup_static_file_handler
-      HANDLERS.insert(2, Kemal::StaticFileHandler.new(@public_folder)) if @serve_static
+      HANDLERS.insert(3, Kemal::StaticFileHandler.new(@public_folder)) if @serve_static
     end
   end
 

src/kemal/init_handler.cr

@@ -0,0 +1,12 @@
+module Kemal
+  # Kemal::InitHandler is the first handler thus initializes the context with default values such as
+  # Content-Type, X-Powered-By.
+  class InitHandler < HTTP::Handler
+    INSTANCE = new
+
+    def call(context)
+      context.response.content_type = "text/html"
+      context.response.headers.add "X-Powered-By", "Kemal"
+    end
+  end
+end

src/kemal/route_handler.cr

@@ -13,8 +13,6 @@ module Kemal
     end
 
     def call(context)
-      context.response.headers.add "X-Powered-By", "Kemal"
-      context.response.content_type = "text/html" unless context.response.headers.has_key?("Content-Type")
       process_request(context)
     end
 

src/kemal/view.cr

@@ -48,7 +48,6 @@ def render_500(context, backtrace, verbosity)
       </body>
       </html>
   HTML
-  context.response.content_type = "text/html"
   context.response.status_code = 500
   context.response.print template
   context