433 lines
14 KiB
Python
433 lines
14 KiB
Python
# (c) 2005 Ian Bicking and contributors; written for Paste (http://pythonpaste.org)
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# Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php
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# Also licenced under the Apache License, 2.0: http://opensource.org/licenses/apache2.0.php
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# Licensed to PSF under a Contributor Agreement
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"""
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Middleware to check for obedience to the WSGI specification.
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Some of the things this checks:
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* Signature of the application and start_response (including that
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keyword arguments are not used).
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* Environment checks:
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- Environment is a dictionary (and not a subclass).
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- That all the required keys are in the environment: REQUEST_METHOD,
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SERVER_NAME, SERVER_PORT, wsgi.version, wsgi.input, wsgi.errors,
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wsgi.multithread, wsgi.multiprocess, wsgi.run_once
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- That HTTP_CONTENT_TYPE and HTTP_CONTENT_LENGTH are not in the
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environment (these headers should appear as CONTENT_LENGTH and
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CONTENT_TYPE).
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- Warns if QUERY_STRING is missing, as the cgi module acts
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unpredictably in that case.
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- That CGI-style variables (that don't contain a .) have
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(non-unicode) string values
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- That wsgi.version is a tuple
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- That wsgi.url_scheme is 'http' or 'https' (@@: is this too
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restrictive?)
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- Warns if the REQUEST_METHOD is not known (@@: probably too
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restrictive).
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- That SCRIPT_NAME and PATH_INFO are empty or start with /
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- That at least one of SCRIPT_NAME or PATH_INFO are set.
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- That CONTENT_LENGTH is a positive integer.
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- That SCRIPT_NAME is not '/' (it should be '', and PATH_INFO should
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be '/').
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- That wsgi.input has the methods read, readline, readlines, and
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__iter__
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- That wsgi.errors has the methods flush, write, writelines
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* The status is a string, contains a space, starts with an integer,
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and that integer is in range (> 100).
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* That the headers is a list (not a subclass, not another kind of
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sequence).
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* That the items of the headers are tuples of strings.
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* That there is no 'status' header (that is used in CGI, but not in
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WSGI).
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* That the headers don't contain newlines or colons, end in _ or -, or
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contain characters codes below 037.
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* That Content-Type is given if there is content (CGI often has a
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default content type, but WSGI does not).
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* That no Content-Type is given when there is no content (@@: is this
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too restrictive?)
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* That the exc_info argument to start_response is a tuple or None.
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* That all calls to the writer are with strings, and no other methods
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on the writer are accessed.
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* That wsgi.input is used properly:
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- .read() is called with zero or one argument
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- That it returns a string
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- That readline, readlines, and __iter__ return strings
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- That .close() is not called
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- No other methods are provided
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* That wsgi.errors is used properly:
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- .write() and .writelines() is called with a string
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- That .close() is not called, and no other methods are provided.
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* The response iterator:
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- That it is not a string (it should be a list of a single string; a
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string will work, but perform horribly).
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- That .next() returns a string
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- That the iterator is not iterated over until start_response has
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been called (that can signal either a server or application
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error).
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- That .close() is called (doesn't raise exception, only prints to
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sys.stderr, because we only know it isn't called when the object
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is garbage collected).
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"""
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__all__ = ['validator']
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import re
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import sys
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from types import DictType, StringType, TupleType, ListType
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import warnings
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header_re = re.compile(r'^[a-zA-Z][a-zA-Z0-9\-_]*$')
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bad_header_value_re = re.compile(r'[\000-\037]')
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class WSGIWarning(Warning):
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"""
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Raised in response to WSGI-spec-related warnings
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"""
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def assert_(cond, *args):
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if not cond:
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raise AssertionError(*args)
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def validator(application):
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"""
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When applied between a WSGI server and a WSGI application, this
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middleware will check for WSGI compliancy on a number of levels.
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This middleware does not modify the request or response in any
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way, but will raise an AssertionError if anything seems off
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(except for a failure to close the application iterator, which
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will be printed to stderr -- there's no way to raise an exception
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at that point).
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"""
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def lint_app(*args, **kw):
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assert_(len(args) == 2, "Two arguments required")
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assert_(not kw, "No keyword arguments allowed")
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environ, start_response = args
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check_environ(environ)
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# We use this to check if the application returns without
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# calling start_response:
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start_response_started = []
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def start_response_wrapper(*args, **kw):
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assert_(len(args) == 2 or len(args) == 3, (
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"Invalid number of arguments: %s" % (args,)))
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assert_(not kw, "No keyword arguments allowed")
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status = args[0]
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headers = args[1]
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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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check_status(status)
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check_headers(headers)
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check_content_type(status, headers)
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check_exc_info(exc_info)
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start_response_started.append(None)
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return WriteWrapper(start_response(*args))
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environ['wsgi.input'] = InputWrapper(environ['wsgi.input'])
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environ['wsgi.errors'] = ErrorWrapper(environ['wsgi.errors'])
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iterator = application(environ, start_response_wrapper)
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assert_(iterator is not None and iterator != False,
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"The application must return an iterator, if only an empty list")
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check_iterator(iterator)
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return IteratorWrapper(iterator, start_response_started)
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return lint_app
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class InputWrapper:
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def __init__(self, wsgi_input):
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self.input = wsgi_input
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def read(self, *args):
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assert_(len(args) <= 1)
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v = self.input.read(*args)
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assert_(type(v) is type(""))
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return v
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def readline(self):
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v = self.input.readline()
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assert_(type(v) is type(""))
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return v
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def readlines(self, *args):
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assert_(len(args) <= 1)
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lines = self.input.readlines(*args)
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assert_(type(lines) is type([]))
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for line in lines:
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assert_(type(line) is type(""))
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return lines
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def __iter__(self):
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while 1:
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line = self.readline()
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if not line:
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return
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yield line
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def close(self):
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assert_(0, "input.close() must not be called")
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class ErrorWrapper:
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def __init__(self, wsgi_errors):
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self.errors = wsgi_errors
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def write(self, s):
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assert_(type(s) is type(""))
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self.errors.write(s)
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def flush(self):
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self.errors.flush()
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def writelines(self, seq):
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for line in seq:
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self.write(line)
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def close(self):
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assert_(0, "errors.close() must not be called")
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class WriteWrapper:
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def __init__(self, wsgi_writer):
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self.writer = wsgi_writer
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def __call__(self, s):
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assert_(type(s) is type(""))
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self.writer(s)
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class PartialIteratorWrapper:
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def __init__(self, wsgi_iterator):
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self.iterator = wsgi_iterator
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def __iter__(self):
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# We want to make sure __iter__ is called
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return IteratorWrapper(self.iterator, None)
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class IteratorWrapper:
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def __init__(self, wsgi_iterator, check_start_response):
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self.original_iterator = wsgi_iterator
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self.iterator = iter(wsgi_iterator)
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self.closed = False
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self.check_start_response = check_start_response
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def __iter__(self):
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return self
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def next(self):
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assert_(not self.closed,
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"Iterator read after closed")
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v = self.iterator.next()
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if self.check_start_response is not None:
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assert_(self.check_start_response,
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"The application returns and we started iterating over its body, but start_response has not yet been called")
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self.check_start_response = None
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return v
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def close(self):
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self.closed = True
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if hasattr(self.original_iterator, 'close'):
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self.original_iterator.close()
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def __del__(self):
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if not self.closed:
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sys.stderr.write(
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"Iterator garbage collected without being closed")
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assert_(self.closed,
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"Iterator garbage collected without being closed")
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def check_environ(environ):
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assert_(type(environ) is DictType,
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"Environment is not of the right type: %r (environment: %r)"
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% (type(environ), environ))
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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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assert_(key in environ,
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"Environment missing required key: %r" % (key,))
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for key in ['HTTP_CONTENT_TYPE', 'HTTP_CONTENT_LENGTH']:
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assert_(key not in environ,
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"Environment should not have the key: %s "
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"(use %s instead)" % (key, key[5:]))
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if 'QUERY_STRING' not in environ:
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warnings.warn(
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'QUERY_STRING is not in the WSGI environment; the cgi '
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'module will use sys.argv when this variable is missing, '
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'so application errors are more likely',
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WSGIWarning)
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for key in environ.keys():
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if '.' in key:
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# Extension, we don't care about its type
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continue
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assert_(type(environ[key]) is StringType,
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"Environmental variable %s is not a string: %r (value: %r)"
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% (key, type(environ[key]), environ[key]))
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assert_(type(environ['wsgi.version']) is TupleType,
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"wsgi.version should be a tuple (%r)" % (environ['wsgi.version'],))
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assert_(environ['wsgi.url_scheme'] in ('http', 'https'),
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"wsgi.url_scheme unknown: %r" % environ['wsgi.url_scheme'])
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check_input(environ['wsgi.input'])
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check_errors(environ['wsgi.errors'])
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# @@: these need filling out:
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if environ['REQUEST_METHOD'] not in (
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'GET', 'HEAD', 'POST', 'OPTIONS','PUT','DELETE','TRACE'):
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warnings.warn(
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"Unknown REQUEST_METHOD: %r" % environ['REQUEST_METHOD'],
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WSGIWarning)
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assert_(not environ.get('SCRIPT_NAME')
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or environ['SCRIPT_NAME'].startswith('/'),
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"SCRIPT_NAME doesn't start with /: %r" % environ['SCRIPT_NAME'])
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assert_(not environ.get('PATH_INFO')
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or environ['PATH_INFO'].startswith('/'),
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"PATH_INFO doesn't start with /: %r" % environ['PATH_INFO'])
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if environ.get('CONTENT_LENGTH'):
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assert_(int(environ['CONTENT_LENGTH']) >= 0,
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"Invalid CONTENT_LENGTH: %r" % environ['CONTENT_LENGTH'])
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if not environ.get('SCRIPT_NAME'):
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assert_('PATH_INFO' in environ,
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"One of SCRIPT_NAME or PATH_INFO are required (PATH_INFO "
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"should at least be '/' if SCRIPT_NAME is empty)")
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assert_(environ.get('SCRIPT_NAME') != '/',
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"SCRIPT_NAME cannot be '/'; it should instead be '', and "
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"PATH_INFO should be '/'")
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def check_input(wsgi_input):
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for attr in ['read', 'readline', 'readlines', '__iter__']:
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assert_(hasattr(wsgi_input, attr),
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"wsgi.input (%r) doesn't have the attribute %s"
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% (wsgi_input, attr))
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def check_errors(wsgi_errors):
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for attr in ['flush', 'write', 'writelines']:
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assert_(hasattr(wsgi_errors, attr),
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"wsgi.errors (%r) doesn't have the attribute %s"
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% (wsgi_errors, attr))
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def check_status(status):
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assert_(type(status) is StringType,
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"Status must be a string (not %r)" % status)
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# Implicitly check that we can turn it into an integer:
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status_code = status.split(None, 1)[0]
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assert_(len(status_code) == 3,
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"Status codes must be three characters: %r" % status_code)
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status_int = int(status_code)
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assert_(status_int >= 100, "Status code is invalid: %r" % status_int)
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if len(status) < 4 or status[3] != ' ':
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warnings.warn(
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"The status string (%r) should be a three-digit integer "
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"followed by a single space and a status explanation"
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% status, WSGIWarning)
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def check_headers(headers):
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assert_(type(headers) is ListType,
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"Headers (%r) must be of type list: %r"
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% (headers, type(headers)))
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header_names = {}
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for item in headers:
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assert_(type(item) is TupleType,
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"Individual headers (%r) must be of type tuple: %r"
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% (item, type(item)))
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assert_(len(item) == 2)
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name, value = item
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assert_(name.lower() != 'status',
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"The Status header cannot be used; it conflicts with CGI "
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"script, and HTTP status is not given through headers "
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"(value: %r)." % value)
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header_names[name.lower()] = None
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assert_('\n' not in name and ':' not in name,
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"Header names may not contain ':' or '\\n': %r" % name)
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assert_(header_re.search(name), "Bad header name: %r" % name)
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assert_(not name.endswith('-') and not name.endswith('_'),
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"Names may not end in '-' or '_': %r" % name)
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if bad_header_value_re.search(value):
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assert_(0, "Bad header value: %r (bad char: %r)"
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% (value, bad_header_value_re.search(value).group(0)))
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def check_content_type(status, headers):
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code = int(status.split(None, 1)[0])
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# @@: need one more person to verify this interpretation of RFC 2616
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# http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html
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NO_MESSAGE_BODY = (204, 304)
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for name, value in headers:
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if name.lower() == 'content-type':
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if code not in NO_MESSAGE_BODY:
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return
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assert_(0, ("Content-Type header found in a %s response, "
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"which must not return content.") % code)
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if code not in NO_MESSAGE_BODY:
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assert_(0, "No Content-Type header found in headers (%s)" % headers)
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def check_exc_info(exc_info):
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assert_(exc_info is None or type(exc_info) is type(()),
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"exc_info (%r) is not a tuple: %r" % (exc_info, type(exc_info)))
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# More exc_info checks?
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def check_iterator(iterator):
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# Technically a string is legal, which is why it's a really bad
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# idea, because it may cause the response to be returned
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# character-by-character
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assert_(not isinstance(iterator, str),
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"You should not return a string as your application iterator, "
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"instead return a single-item list containing that string.")
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