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This middleware rescues any exception returned by the application and calls an exceptions app that will wrap it in a format for the end user.

The exceptions app should be passed as a parameter on initialization of ShowExceptions. Every time there is an exception, ShowExceptions will store the exception in env["action_dispatch.exception"], rewrite the PATH_INFO to the exception status code and call the Rack app.

In Rails applications, the exceptions app can be configured with config.exceptions_app, which defaults to ActionDispatch::PublicExceptions.

If the application returns an "X-Cascade" => "pass" response, this middleware will send an empty response as a result with the correct status code. If any exception happens inside the exceptions app, this middleware catches the exceptions and returns a failsafe response.


Class Public methods

new(app, exceptions_app)

# File actionpack/lib/action_dispatch/middleware/show_exceptions.rb, line 22
def initialize(app, exceptions_app)
  @app = app
  @exceptions_app = exceptions_app

Instance Public methods


# File actionpack/lib/action_dispatch/middleware/show_exceptions.rb, line 27
def call(env)
  request = env
rescue Exception => exception
  if request.show_exceptions?
    render_exception(request, exception)
    raise exception