Add paste.lint as wsgiref.validate

git-svn-id: svn://svn.eby-sarna.com/svnroot/wsgiref@2166 571e12c6-e1fa-0310-aee7-ff1267fa46bd

2 files changed, 440 insertions, 10 deletions

diff --git a/src/wsgiref/__init__.py b/src/wsgiref/__init__.py
index 9f37850..46c579f 100644
--- a/src/wsgiref/__init__.py
+++ b/src/wsgiref/__init__.py
@@ -2,21 +2,22 @@
 
 Current Contents:
 
-    * util -- Miscellaneous useful functions and wrappers
+* util -- Miscellaneous useful functions and wrappers
 
-    * headers -- Manage response headers
+* headers -- Manage response headers
 
-    * handlers -- base classes for server/gateway implementations
+* handlers -- base classes for server/gateway implementations
 
-    * simple_server -- a simple BaseHTTPServer that supports WSGI
-    
-To-Do:
+* simple_server -- a simple BaseHTTPServer that supports WSGI
+
+* validate -- validation wrapper that sits between an app and a server
+  to detect errors in either
 
-    * validate -- validation library and "lint"-like functions
+To-Do:
 
-    * cgi_gateway -- Run WSGI apps under CGI
+* cgi_gateway -- Run WSGI apps under CGI (pending a deployment standard)
 
-    * cgi_wrapper -- Run CGI apps under WSGI
+* cgi_wrapper -- Run CGI apps under WSGI
 
-    * router -- a simple middleware component that handles URL traversal
+* router -- a simple middleware component that handles URL traversal
 """
diff --git a/src/wsgiref/validate.py b/src/wsgiref/validate.py
new file mode 100755
index 0000000..af903df
--- /dev/null
+++ b/src/wsgiref/validate.py
@@ -0,0 +1,429 @@
+# (c) 2005 Ian Bicking and contributors; written for Paste (http://pythonpaste.org)
+# Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php
+# Also licenced under the Apache License, 2.0: http://opensource.org/licenses/apache2.0.php
+# Licensed to PSF under a Contributor Agreement
+"""
+Middleware to check for obedience to the WSGI specification.
+
+Some of the things this checks:
+
+* Signature of the application and start_response (including that
+  keyword arguments are not used).
+
+* Environment checks:
+
+  - Environment is a dictionary (and not a subclass).
+
+  - That all the required keys are in the environment: REQUEST_METHOD,
+    SERVER_NAME, SERVER_PORT, wsgi.version, wsgi.input, wsgi.errors,
+    wsgi.multithread, wsgi.multiprocess, wsgi.run_once
+
+  - That HTTP_CONTENT_TYPE and HTTP_CONTENT_LENGTH are not in the
+    environment (these headers should appear as CONTENT_LENGTH and
+    CONTENT_TYPE).
+
+  - Warns if QUERY_STRING is missing, as the cgi module acts
+    unpredictably in that case.
+
+  - That CGI-style variables (that don't contain a .) have
+    (non-unicode) string values
+
+  - That wsgi.version is a tuple
+
+  - That wsgi.url_scheme is 'http' or 'https' (@@: is this too
+    restrictive?)
+
+  - Warns if the REQUEST_METHOD is not known (@@: probably too
+    restrictive).
+
+  - That SCRIPT_NAME and PATH_INFO are empty or start with /
+
+  - That at least one of SCRIPT_NAME or PATH_INFO are set.
+
+  - That CONTENT_LENGTH is a positive integer.
+
+  - That SCRIPT_NAME is not '/' (it should be '', and PATH_INFO should
+    be '/').
+
+  - That wsgi.input has the methods read, readline, readlines, and
+    __iter__
+
+  - That wsgi.errors has the methods flush, write, writelines
+
+* The status is a string, contains a space, starts with an integer,
+  and that integer is in range (> 100).
+
+* That the headers is a list (not a subclass, not another kind of
+  sequence).
+
+* That the items of the headers are tuples of strings.
+
+* That there is no 'status' header (that is used in CGI, but not in
+  WSGI).
+
+* That the headers don't contain newlines or colons, end in _ or -, or
+  contain characters codes below 037.
+
+* That Content-Type is given if there is content (CGI often has a
+  default content type, but WSGI does not).
+
+* That no Content-Type is given when there is no content (@@: is this
+  too restrictive?)
+
+* That the exc_info argument to start_response is a tuple or None.
+
+* That all calls to the writer are with strings, and no other methods
+  on the writer are accessed.
+
+* That wsgi.input is used properly:
+
+  - .read() is called with zero or one argument
+
+  - That it returns a string
+
+  - That readline, readlines, and __iter__ return strings
+
+  - That .close() is not called
+
+  - No other methods are provided
+
+* That wsgi.errors is used properly:
+
+  - .write() and .writelines() is called with a string
+
+  - That .close() is not called, and no other methods are provided.
+
+* The response iterator:
+
+  - That it is not a string (it should be a list of a single string; a
+    string will work, but perform horribly).
+
+  - That .next() returns a string
+
+  - That the iterator is not iterated over until start_response has
+    been called (that can signal either a server or application
+    error).
+
+  - That .close() is called (doesn't raise exception, only prints to
+    sys.stderr, because we only know it isn't called when the object
+    is garbage collected).
+"""
+__all__ = ['middleware']
+
+
+import re
+import sys
+from types import DictType, StringType, TupleType, ListType
+import warnings
+
+header_re = re.compile(r'^[a-zA-Z][a-zA-Z0-9\-_]*$')
+bad_header_value_re = re.compile(r'[\000-\037]')
+
+class WSGIWarning(Warning):
+    """
+    Raised in response to WSGI-spec-related warnings
+    """
+
+def middleware(application):
+
+    """
+    When applied between a WSGI server and a WSGI application, this
+    middleware will check for WSGI compliancy on a number of levels.
+    This middleware does not modify the request or response in any
+    way, but will throw an AssertionError if anything seems off
+    (except for a failure to close the application iterator, which
+    will be printed to stderr -- there's no way to throw an exception
+    at that point).
+    """
+
+    def lint_app(*args, **kw):
+        assert len(args) == 2, "Two arguments required"
+        assert not kw, "No keyword arguments allowed"
+        environ, start_response = args
+
+        check_environ(environ)
+
+        # We use this to check if the application returns without
+        # calling start_response:
+        start_response_started = []
+
+        def start_response_wrapper(*args, **kw):
+            assert len(args) == 2 or len(args) == 3, (
+                "Invalid number of arguments: %s" % args)
+            assert not kw, "No keyword arguments allowed"
+            status = args[0]
+            headers = args[1]
+            if len(args) == 3:
+                exc_info = args[2]
+            else:
+                exc_info = None
+
+            check_status(status)
+            check_headers(headers)
+            check_content_type(status, headers)
+            check_exc_info(exc_info)
+
+            start_response_started.append(None)
+            return WriteWrapper(start_response(*args))
+
+        environ['wsgi.input'] = InputWrapper(environ['wsgi.input'])
+        environ['wsgi.errors'] = ErrorWrapper(environ['wsgi.errors'])
+
+        iterator = application(environ, start_response_wrapper)
+        assert iterator is not None and iterator != False, (
+            "The application must return an iterator, if only an empty list")
+
+        check_iterator(iterator)
+
+        return IteratorWrapper(iterator, start_response_started)
+
+    return lint_app
+
+class InputWrapper:
+
+    def __init__(self, wsgi_input):
+        self.input = wsgi_input
+
+    def read(self, *args):
+        assert len(args) <= 1
+        v = self.input.read(*args)
+        assert type(v) is type("")
+        return v
+
+    def readline(self):
+        v = self.input.readline()
+        assert type(v) is type("")
+        return v
+
+    def readlines(self, *args):
+        assert len(args) <= 1
+        lines = self.input.readlines(*args)
+        assert type(lines) is type([])
+        for line in lines:
+            assert type(line) is type("")
+        return lines
+
+    def __iter__(self):
+        while 1:
+            line = self.readline()
+            if not line:
+                return
+            yield line
+
+    def close(self):
+        assert 0, "input.close() must not be called"
+
+class ErrorWrapper:
+
+    def __init__(self, wsgi_errors):
+        self.errors = wsgi_errors
+
+    def write(self, s):
+        assert type(s) is type("")
+        self.errors.write(s)
+
+    def flush(self):
+        self.errors.flush()
+
+    def writelines(self, seq):
+        for line in seq:
+            self.write(line)
+
+    def close(self):
+        assert 0, "errors.close() must not be called"
+
+class WriteWrapper:
+
+    def __init__(self, wsgi_writer):
+        self.writer = wsgi_writer
+
+    def __call__(self, s):
+        assert type(s) is type("")
+        self.writer(s)
+
+class PartialIteratorWrapper:
+
+    def __init__(self, wsgi_iterator):
+        self.iterator = wsgi_iterator
+
+    def __iter__(self):
+        # We want to make sure __iter__ is called
+        return IteratorWrapper(self.iterator)
+
+class IteratorWrapper:
+
+    def __init__(self, wsgi_iterator, check_start_response):
+        self.original_iterator = wsgi_iterator
+        self.iterator = iter(wsgi_iterator)
+        self.closed = False
+        self.check_start_response = check_start_response
+
+    def __iter__(self):
+        return self
+
+    def next(self):
+        assert not self.closed, (
+            "Iterator read after closed")
+        v = self.iterator.next()
+        if self.check_start_response is not None:
+            assert self.check_start_response, (
+                "The application returns and we started iterating over its body, but start_response has not yet been called")
+            self.check_start_response = None
+        return v
+
+    def close(self):
+        self.closed = True
+        if hasattr(self.original_iterator, 'close'):
+            self.original_iterator.close()
+
+    def __del__(self):
+        if not self.closed:
+            sys.stderr.write(
+                "Iterator garbage collected without being closed")
+        assert self.closed, (
+            "Iterator garbage collected without being closed")
+
+def check_environ(environ):
+    assert type(environ) is DictType, (
+        "Environment is not of the right type: %r (environment: %r)"
+        % (type(environ), environ))
+
+    for key in ['REQUEST_METHOD', 'SERVER_NAME', 'SERVER_PORT',
+                'wsgi.version', 'wsgi.input', 'wsgi.errors',
+                'wsgi.multithread', 'wsgi.multiprocess',
+                'wsgi.run_once']:
+        assert key in environ, (
+            "Environment missing required key: %r" % key)
+
+    for key in ['HTTP_CONTENT_TYPE', 'HTTP_CONTENT_LENGTH']:
+        assert key not in environ, (
+            "Environment should not have the key: %s "
+            "(use %s instead)" % (key, key[5:]))
+
+    if 'QUERY_STRING' not in environ:
+        warnings.warn(
+            'QUERY_STRING is not in the WSGI environment; the cgi '
+            'module will use sys.argv when this variable is missing, '
+            'so application errors are more likely',
+            WSGIWarning)
+
+    for key in environ.keys():
+        if '.' in key:
+            # Extension, we don't care about its type
+            continue
+        assert type(environ[key]) is StringType, (
+            "Environmental variable %s is not a string: %r (value: %r)"
+            % (type(environ[key]), environ[key]))
+
+    assert type(environ['wsgi.version']) is TupleType, (
+        "wsgi.version should be a tuple (%r)" % environ['wsgi.version'])
+    assert environ['wsgi.url_scheme'] in ('http', 'https'), (
+        "wsgi.url_scheme unknown: %r" % environ['wsgi.url_scheme'])
+
+    check_input(environ['wsgi.input'])
+    check_errors(environ['wsgi.errors'])
+
+    # @@: these need filling out:
+    if environ['REQUEST_METHOD'] not in (
+        'GET', 'HEAD', 'POST', 'OPTIONS','PUT','DELETE','TRACE'):
+        warnings.warn(
+            "Unknown REQUEST_METHOD: %r" % environ['REQUEST_METHOD'],
+            WSGIWarning)
+
+    assert (not environ.get('SCRIPT_NAME')
+            or environ['SCRIPT_NAME'].startswith('/')), (
+        "SCRIPT_NAME doesn't start with /: %r" % environ['SCRIPT_NAME'])
+    assert (not environ.get('PATH_INFO')
+            or environ['PATH_INFO'].startswith('/')), (
+        "PATH_INFO doesn't start with /: %r" % environ['PATH_INFO'])
+    if environ.get('CONTENT_LENGTH'):
+        assert int(environ['CONTENT_LENGTH']) >= 0, (
+            "Invalid CONTENT_LENGTH: %r" % environ['CONTENT_LENGTH'])
+
+    if not environ.get('SCRIPT_NAME'):
+        assert environ.has_key('PATH_INFO'), (
+            "One of SCRIPT_NAME or PATH_INFO are required (PATH_INFO "
+            "should at least be '/' if SCRIPT_NAME is empty)")
+    assert environ.get('SCRIPT_NAME') != '/', (
+        "SCRIPT_NAME cannot be '/'; it should instead be '', and "
+        "PATH_INFO should be '/'")
+
+def check_input(wsgi_input):
+    for attr in ['read', 'readline', 'readlines', '__iter__']:
+        assert hasattr(wsgi_input, attr), (
+            "wsgi.input (%r) doesn't have the attribute %s"
+            % (wsgi_input, attr))
+
+def check_errors(wsgi_errors):
+    for attr in ['flush', 'write', 'writelines']:
+        assert hasattr(wsgi_errors, attr), (
+            "wsgi.errors (%r) doesn't have the attribute %s"
+            % (wsgi_errors, attr))
+
+def check_status(status):
+    assert type(status) is StringType, (
+        "Status must be a string (not %r)" % status)
+    # Implicitly check that we can turn it into an integer:
+    status_code = status.split(None, 1)[0]
+    assert len(status_code) == 3, (
+        "Status codes must be three characters: %r" % status_code)
+    status_int = int(status_code)
+    assert status_int >= 100, "Status code is invalid: %r" % status_int
+    if len(status) < 4 or status[3] != ' ':
+        warnings.warn(
+            "The status string (%r) should be a three-digit integer "
+            "followed by a single space and a status explanation"
+            % status, WSGIWarning)
+
+def check_headers(headers):
+    assert type(headers) is ListType, (
+        "Headers (%r) must be of type list: %r"
+        % (headers, type(headers)))
+    header_names = {}
+    for item in headers:
+        assert type(item) is TupleType, (
+            "Individual headers (%r) must be of type tuple: %r"
+            % (item, type(item)))
+        assert len(item) == 2
+        name, value = item
+        assert name.lower() != 'status', (
+            "The Status header cannot be used; it conflicts with CGI "
+            "script, and HTTP status is not given through headers "
+            "(value: %r)." % value)
+        header_names[name.lower()] = None
+        assert '\n' not in name and ':' not in name, (
+            "Header names may not contain ':' or '\\n': %r" % name)
+        assert header_re.search(name), "Bad header name: %r" % name
+        assert not name.endswith('-') and not name.endswith('_'), (
+            "Names may not end in '-' or '_': %r" % name)
+        assert not bad_header_value_re.search(value), (
+            "Bad header value: %r (bad char: %r)"
+            % (value, bad_header_value_re.search(value).group(0)))
+
+def check_content_type(status, headers):
+    code = int(status.split(None, 1)[0])
+    # @@: need one more person to verify this interpretation of RFC 2616
+    #     http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html
+    NO_MESSAGE_BODY = (204, 304)
+    for name, value in headers:
+        if name.lower() == 'content-type':
+            if code not in NO_MESSAGE_BODY:
+                return
+            assert 0, (("Content-Type header found in a %s response, "
+                        "which must not return content.") % code)
+    if code not in NO_MESSAGE_BODY:
+        assert 0, "No Content-Type header found in headers (%s)" % headers
+
+def check_exc_info(exc_info):
+    assert exc_info is None or type(exc_info) is type(()), (
+        "exc_info (%r) is not a tuple: %r" % (exc_info, type(exc_info)))
+    # More exc_info checks?
+
+def check_iterator(iterator):
+    # Technically a string is legal, which is why it's a really bad
+    # idea, because it may cause the response to be returned
+    # character-by-character
+    assert not isinstance(iterator, str), (
+        "You should not return a string as your application iterator, "
+        "instead return a single-item list containing that string.")
+