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343 lines
12 KiB
343 lines
12 KiB
# -*- coding: utf-8 -*-
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"""
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werkzeug.contrib.lint
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~~~~~~~~~~~~~~~~~~~~~
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.. versionadded:: 0.5
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This module provides a middleware that performs sanity checks of the WSGI
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application. It checks that :pep:`333` is properly implemented and warns
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on some common HTTP errors such as non-empty responses for 304 status
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codes.
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This module provides a middleware, the :class:`LintMiddleware`. Wrap your
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application with it and it will warn about common problems with WSGI and
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HTTP while your application is running.
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It's strongly recommended to use it during development.
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:copyright: (c) 2014 by the Werkzeug Team, see AUTHORS for more details.
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:license: BSD, see LICENSE for more details.
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"""
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try:
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from urllib.parse import urlparse
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except ImportError:
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from urlparse import urlparse
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from warnings import warn
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from werkzeug.datastructures import Headers
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from werkzeug.http import is_entity_header
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from werkzeug.wsgi import FileWrapper
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from werkzeug._compat import string_types
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class WSGIWarning(Warning):
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"""Warning class for WSGI warnings."""
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class HTTPWarning(Warning):
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"""Warning class for HTTP warnings."""
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def check_string(context, obj, stacklevel=3):
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if type(obj) is not str:
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warn(WSGIWarning('%s requires bytestrings, got %s' %
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(context, obj.__class__.__name__)))
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class InputStream(object):
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def __init__(self, stream):
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self._stream = stream
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def read(self, *args):
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if len(args) == 0:
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warn(WSGIWarning('wsgi does not guarantee an EOF marker on the '
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'input stream, thus making calls to '
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'wsgi.input.read() unsafe. Conforming servers '
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'may never return from this call.'),
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stacklevel=2)
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elif len(args) != 1:
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warn(WSGIWarning('too many parameters passed to wsgi.input.read()'),
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stacklevel=2)
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return self._stream.read(*args)
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def readline(self, *args):
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if len(args) == 0:
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warn(WSGIWarning('Calls to wsgi.input.readline() without arguments'
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' are unsafe. Use wsgi.input.read() instead.'),
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stacklevel=2)
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elif len(args) == 1:
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warn(WSGIWarning('wsgi.input.readline() was called with a size hint. '
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'WSGI does not support this, although it\'s available '
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'on all major servers.'),
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stacklevel=2)
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else:
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raise TypeError('too many arguments passed to wsgi.input.readline()')
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return self._stream.readline(*args)
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def __iter__(self):
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try:
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return iter(self._stream)
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except TypeError:
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warn(WSGIWarning('wsgi.input is not iterable.'), stacklevel=2)
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return iter(())
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def close(self):
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warn(WSGIWarning('application closed the input stream!'),
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stacklevel=2)
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self._stream.close()
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class ErrorStream(object):
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def __init__(self, stream):
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self._stream = stream
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def write(self, s):
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check_string('wsgi.error.write()', s)
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self._stream.write(s)
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def flush(self):
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self._stream.flush()
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def writelines(self, seq):
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for line in seq:
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self.write(seq)
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def close(self):
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warn(WSGIWarning('application closed the error stream!'),
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stacklevel=2)
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self._stream.close()
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class GuardedWrite(object):
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def __init__(self, write, chunks):
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self._write = write
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self._chunks = chunks
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def __call__(self, s):
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check_string('write()', s)
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self._write.write(s)
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self._chunks.append(len(s))
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class GuardedIterator(object):
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def __init__(self, iterator, headers_set, chunks):
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self._iterator = iterator
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self._next = iter(iterator).next
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self.closed = False
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self.headers_set = headers_set
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self.chunks = chunks
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def __iter__(self):
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return self
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def next(self):
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if self.closed:
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warn(WSGIWarning('iterated over closed app_iter'),
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stacklevel=2)
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rv = self._next()
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if not self.headers_set:
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warn(WSGIWarning('Application returned before it '
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'started the response'), stacklevel=2)
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check_string('application iterator items', rv)
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self.chunks.append(len(rv))
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return rv
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def close(self):
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self.closed = True
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if hasattr(self._iterator, 'close'):
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self._iterator.close()
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if self.headers_set:
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status_code, headers = self.headers_set
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bytes_sent = sum(self.chunks)
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content_length = headers.get('content-length', type=int)
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if status_code == 304:
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for key, value in headers:
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key = key.lower()
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if key not in ('expires', 'content-location') and \
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is_entity_header(key):
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warn(HTTPWarning('entity header %r found in 304 '
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'response' % key))
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if bytes_sent:
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warn(HTTPWarning('304 responses must not have a body'))
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elif 100 <= status_code < 200 or status_code == 204:
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if content_length != 0:
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warn(HTTPWarning('%r responses must have an empty '
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'content length' % status_code))
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if bytes_sent:
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warn(HTTPWarning('%r responses must not have a body' %
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status_code))
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elif content_length is not None and content_length != bytes_sent:
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warn(WSGIWarning('Content-Length and the number of bytes '
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'sent to the client do not match.'))
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def __del__(self):
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if not self.closed:
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try:
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warn(WSGIWarning('Iterator was garbage collected before '
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'it was closed.'))
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except Exception:
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pass
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class LintMiddleware(object):
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"""This middleware wraps an application and warns on common errors.
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Among other thing it currently checks for the following problems:
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- invalid status codes
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- non-bytestrings sent to the WSGI server
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- strings returned from the WSGI application
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- non-empty conditional responses
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- unquoted etags
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- relative URLs in the Location header
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- unsafe calls to wsgi.input
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- unclosed iterators
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Detected errors are emitted using the standard Python :mod:`warnings`
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system and usually end up on :data:`stderr`.
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::
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from werkzeug.contrib.lint import LintMiddleware
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app = LintMiddleware(app)
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:param app: the application to wrap
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"""
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def __init__(self, app):
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self.app = app
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def check_environ(self, environ):
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if type(environ) is not dict:
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warn(WSGIWarning('WSGI environment is not a standard python dict.'),
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stacklevel=4)
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for key in ('REQUEST_METHOD', 'SERVER_NAME', 'SERVER_PORT',
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'wsgi.version', 'wsgi.input', 'wsgi.errors',
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'wsgi.multithread', 'wsgi.multiprocess',
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'wsgi.run_once'):
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if key not in environ:
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warn(WSGIWarning('required environment key %r not found'
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% key), stacklevel=3)
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if environ['wsgi.version'] != (1, 0):
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warn(WSGIWarning('environ is not a WSGI 1.0 environ'),
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stacklevel=3)
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script_name = environ.get('SCRIPT_NAME', '')
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if script_name and script_name[:1] != '/':
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warn(WSGIWarning('SCRIPT_NAME does not start with a slash: %r'
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% script_name), stacklevel=3)
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path_info = environ.get('PATH_INFO', '')
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if path_info[:1] != '/':
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warn(WSGIWarning('PATH_INFO does not start with a slash: %r'
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% path_info), stacklevel=3)
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def check_start_response(self, status, headers, exc_info):
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check_string('status', status)
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status_code = status.split(None, 1)[0]
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if len(status_code) != 3 or not status_code.isdigit():
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warn(WSGIWarning('Status code must be three digits'), stacklevel=3)
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if len(status) < 4 or status[3] != ' ':
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warn(WSGIWarning('Invalid value for status %r. Valid '
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'status strings are three digits, a space '
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'and a status explanation'), stacklevel=3)
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status_code = int(status_code)
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if status_code < 100:
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warn(WSGIWarning('status code < 100 detected'), stacklevel=3)
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if type(headers) is not list:
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warn(WSGIWarning('header list is not a list'), stacklevel=3)
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for item in headers:
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if type(item) is not tuple or len(item) != 2:
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warn(WSGIWarning('Headers must tuple 2-item tuples'),
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stacklevel=3)
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name, value = item
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if type(name) is not str or type(value) is not str:
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warn(WSGIWarning('header items must be strings'),
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stacklevel=3)
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if name.lower() == 'status':
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warn(WSGIWarning('The status header is not supported due to '
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'conflicts with the CGI spec.'),
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stacklevel=3)
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if exc_info is not None and not isinstance(exc_info, tuple):
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warn(WSGIWarning('invalid value for exc_info'), stacklevel=3)
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headers = Headers(headers)
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self.check_headers(headers)
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return status_code, headers
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def check_headers(self, headers):
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etag = headers.get('etag')
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if etag is not None:
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if etag.startswith(('W/', 'w/')):
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if etag.startswith('w/'):
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warn(HTTPWarning('weak etag indicator should be upcase.'),
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stacklevel=4)
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etag = etag[2:]
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if not (etag[:1] == etag[-1:] == '"'):
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warn(HTTPWarning('unquoted etag emitted.'), stacklevel=4)
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location = headers.get('location')
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if location is not None:
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if not urlparse(location).netloc:
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warn(HTTPWarning('absolute URLs required for location header'),
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stacklevel=4)
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def check_iterator(self, app_iter):
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if isinstance(app_iter, string_types):
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warn(WSGIWarning('application returned string. Response will '
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'send character for character to the client '
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'which will kill the performance. Return a '
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'list or iterable instead.'), stacklevel=3)
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def __call__(self, *args, **kwargs):
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if len(args) != 2:
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warn(WSGIWarning('Two arguments to WSGI app required'), stacklevel=2)
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if kwargs:
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warn(WSGIWarning('No keyword arguments to WSGI app allowed'),
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stacklevel=2)
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environ, start_response = args
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self.check_environ(environ)
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environ['wsgi.input'] = InputStream(environ['wsgi.input'])
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environ['wsgi.errors'] = ErrorStream(environ['wsgi.errors'])
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# hook our own file wrapper in so that applications will always
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# iterate to the end and we can check the content length
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environ['wsgi.file_wrapper'] = FileWrapper
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headers_set = []
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chunks = []
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def checking_start_response(*args, **kwargs):
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if len(args) not in (2, 3):
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warn(WSGIWarning('Invalid number of arguments: %s, expected '
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'2 or 3' % len(args), stacklevel=2))
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if kwargs:
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warn(WSGIWarning('no keyword arguments allowed.'))
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status, headers = args[:2]
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if len(args) == 3:
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exc_info = args[2]
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else:
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exc_info = None
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headers_set[:] = self.check_start_response(status, headers,
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exc_info)
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return GuardedWrite(start_response(status, headers, exc_info),
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chunks)
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app_iter = self.app(environ, checking_start_response)
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self.check_iterator(app_iter)
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return GuardedIterator(app_iter, headers_set, chunks)
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