exceptions_app is called with safe format

Author: yskkin

actionpack/lib/action_dispatch/middleware/public_exceptions.rb

@@ -25,11 +25,7 @@ def initialize(public_path)
     def call(env)
       request      = ActionDispatch::Request.new(env)
       status       = request.path_info[1..-1].to_i
-      begin
-        content_type = request.formats.first
-      rescue ActionDispatch::Http::MimeNegotiation::InvalidType
-        content_type = Mime[:text]
-      end
+      content_type = request.formats.first
       body = { status: status, error: Rack::Utils::HTTP_STATUS_CODES.fetch(status, Rack::Utils::HTTP_STATUS_CODES[500]) }
 
       render(status, content_type, body)

guides/source/configuring.md

@@ -370,40 +370,6 @@ Sets up the application-wide encoding. Defaults to UTF-8.
 Sets the exceptions application invoked by the `ShowException` middleware when an exception happens.
 Defaults to `ActionDispatch::PublicExceptions.new(Rails.public_path)`.
 
-Exceptions applications need to handle `ActionDispatch::Http::MimeNegotiation::InvalidType` errors, which are raised when a client sends an invalid `Accept` or `Content-Type` header.
-The default `ActionDispatch::PublicExceptions` application does this automatically, setting `Content-Type` to `text/html` and returning a `406 Not Acceptable` status.
-Failure to handle this error will result in a `500 Internal Server Error`.
-
-Using the `Rails.application.routes` `RouteSet` as the exceptions application also requires this special handling.
-It might look something like this:
-
-```ruby
-# config/application.rb
-config.exceptions_app = CustomExceptionsAppWrapper.new(exceptions_app: routes)
-
-# lib/custom_exceptions_app_wrapper.rb
-class CustomExceptionsAppWrapper
-  def initialize(exceptions_app:)
-    @exceptions_app = exceptions_app
-  end
-
-  def call(env)
-    request = ActionDispatch::Request.new(env)
-
-    fallback_to_html_format_if_invalid_mime_type(request)
-
-    @exceptions_app.call(env)
-  end
-
-  private
-    def fallback_to_html_format_if_invalid_mime_type(request)
-      request.formats
-    rescue ActionDispatch::Http::MimeNegotiation::InvalidType
-      request.set_header "CONTENT_TYPE", "text/html"
-    end
-end
-```
-
 #### `config.file_watcher`
 
 Is the class used to detect file updates in the file system when `config.reload_classes_only_on_change` is `true`. Rails ships with `ActiveSupport::FileUpdateChecker`, the default, and `ActiveSupport::EventedFileUpdateChecker`. Custom classes must conform to the `ActiveSupport::FileUpdateChecker` API.