# `paste.recursive` – internal requests

Middleware to make internal requests and forward requests internally.

When applied, several keys are added to the environment that will allow you to trigger recursive redirects and forwards.

> paste.recursive.include:

>   When you call `environ['paste.recursive.include'](new_path_info)` a response will be returned. The response has a `body` attribute, a `status` attribute, and a `headers` attribute.

> paste.recursive.script_name:

>   The `SCRIPT_NAME` at the point that recursive lives. Only paths underneath this path can be redirected to.

> paste.recursive.old_path_info:

>   A list of previous `PATH_INFO` values from previous redirects.

Raise `ForwardRequestException(new_path_info)` to do a forward (aborting the current request).

## Module Contents

class `paste.recursive.``RecursiveMiddleware`(application, global_conf=None)

  A WSGI middleware that allows for recursive and forwarded calls. All these calls go to the same ‘application’, but presumably that application acts differently with different URLs. The forwarded URLs must be relative to this container.

  Interface is entirely through the `paste.recursive.forward` and `paste.recursive.include` environmental keys.

`paste.recursive.``ForwardRequestException`(url=None, environ={}, factory=None, path_info=None)

  Used to signal that a request should be forwarded to a different location.

  `url`

    The URL to forward to starting with a `/` and relative to `RecursiveMiddleware`. URL fragments can also contain query strings so `/error?code=404` would be a valid URL fragment.

  `environ`

    An altertative WSGI environment dictionary to use for the forwarded request. If specified is used instead of the `url_fragment`

  `factory`

    If specifed `factory` is used instead of `url` or `environ`. `factory` is a callable that takes a WSGI application object as the first argument and returns an initialised WSGI middleware which can alter the forwarded response.

  Basic usage (must have `RecursiveMiddleware` present) :

      from paste.recursive import ForwardRequestException
      def app(environ, start_response):
          if environ['PATH_INFO'] == '/hello':
              start_response("200 OK", [('Content-type', 'text/plain')])
              return [b'Hello World!']
          elif environ['PATH_INFO'] == '/error':
              start_response("404 Not Found", [('Content-type', 'text/plain')])
              return [b'Page not found']
          else:
              raise ForwardRequestException('/error')

      from paste.recursive import RecursiveMiddleware
      app = RecursiveMiddleware(app)

  If you ran this application and visited `/hello` you would get a `Hello World!` message. If you ran the application and visited `/not_found` a `ForwardRequestException` would be raised and the caught by the `RecursiveMiddleware`. The `RecursiveMiddleware` would then return the headers and response from the `/error` URL but would display a `404 Not found` status message.

  You could also specify an `environ` dictionary instead of a url. Using the same example as before:

      def app(environ, start_response):
          ... same as previous example ...
          else:
              new_environ = environ.copy()
              new_environ['PATH_INFO'] = '/error'
              raise ForwardRequestException(environ=new_environ)

  Finally, if you want complete control over every aspect of the forward you can specify a middleware factory. For example to keep the old status code but use the headers and resposne body from the forwarded response you might do this:

      from paste.recursive import ForwardRequestException
      from paste.recursive import RecursiveMiddleware
      from paste.errordocument import StatusKeeper

      def app(environ, start_response):
          if environ['PATH_INFO'] == '/hello':
              start_response("200 OK", [('Content-type', 'text/plain')])
              return [b'Hello World!']
          elif environ['PATH_INFO'] == '/error':
              start_response("404 Not Found", [('Content-type', 'text/plain')])
              return [b'Page not found']
          else:
              def factory(app):
                  return StatusKeeper(app, status='404 Not Found', url='/error')
              raise ForwardRequestException(factory=factory)

      app = RecursiveMiddleware(app)