# Werkzeug

# Lint Validation Middleware

New in version 0.5.

This module provides a middleware that performs sanity checks of the WSGI application. It checks that PEP 333 is properly implemented and warns on some common HTTP errors such as non-empty responses for 304 status codes.

This module provides a middleware, the `LintMiddleware`. Wrap your application with it and it will warn about common problems with WSGI and HTTP while your application is running.

It’s strongly recommended to use it during development.

class `werkzeug.contrib.lint.``LintMiddleware`(app)

  This middleware wraps an application and warns on common errors. Among other thing it currently checks for the following problems:

  - invalid status codes
  - non-bytestrings sent to the WSGI server
  - strings returned from the WSGI application
  - non-empty conditional responses
  - unquoted etags
  - relative URLs in the Location header
  - unsafe calls to wsgi.input
  - unclosed iterators

  Detected errors are emitted using the standard Python `warnings` system and usually end up on `stderr`.

      from werkzeug.contrib.lint import LintMiddleware
      app = LintMiddleware(app)

  Parameter: | app – the application to wrap