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import os
import sys
import imp
import wsgilib
from paste.docsupport import metadata
class NoDefault:
pass
__all__ = ['URLParser', 'StaticURLParser']
class URLParser(object):
"""
WSGI middleware
Application dispatching, based on URL. An instance of `URLParser` is
an application that loads and delegates to other applications. It
looks for files in its directory that match the first part of
PATH_INFO; these may have an extension, but are not required to have
one, in which case the available files are searched to find the
appropriate file. If it is ambiguous, a 404 is returned and an error
logged.
By default there is a constructor for .py files that loads the module,
and looks for an attribute ``application``, which is a ready
application object, or an attribute that matches the module name,
which is a factory for building applications, and is called with no
arguments.
URLParser will also look in __init__.py for special overrides.
These overrides are:
``urlparser_hook(environ)``
This can modified the environment. Its return value is ignored,
and it cannot be used to change the response in any way. You
*can* use this, for example, to manipulate SCRIPT_NAME/PATH_INFO
(try to keep them consistent with the original URL -- but
consuming PATH_INFO and moving that to SCRIPT_NAME is ok).
``urlparser_wrap(environ, start_response, app)``:
After URLParser finds the application, it calls this function
(if present). If this function doesn't call
``app(environ, start_response)`` then the application won't be
called at all! This can be used to allocate resources (with
``try:finally:``) or otherwise filter the output of the
application.
``not_found_hook(environ, start_response)``:
If no file can be found (*in this directory*) to match the
request, then this WSGI application will be called. You can
use this to change the URL and pass the request back to
URLParser again, or on to some other application. This
doesn't catch all ``404 Not Found`` responses, just missing
files.
``application(environ, start_response)``:
This basically overrides URLParser completely, and the given
application is used for all requests. ``urlparser_wrap`` and
``urlparser_hook`` are still called, but the filesystem isn't
searched in any way.
"""
_config_index_name = metadata.Config(
"""
A list of allowed names for the index file (the file served
for requests that end in ``/``).
""", default=['index', 'Index', 'main', 'Main'])
_config_hide_extensions = metadata.Config(
"""
A list of extensions (with leading ``.``) that should not ever
be served.""", default=['.pyc', '.bak', '.py~'])
_config_ignore_extensions = metadata.Config(
"""
Extensions that will be ignored when searching for a file. If
the extension is given explicitly, files with these extensions
will still be served.""", default=[])
_config_constructors = metadata.Config(
"""
A dictionary of extensions as keys, and application constructors
as values. Also the key ``dir`` for directories, and ``*`` when
no other constructor is found.
Each constructor is called like ``constructor(environ, filename)``
and should return an application or ``None``.
""")
default_options = {
'index_names': ['index', 'Index', 'main', 'Main'],
'hide_extensions': ['.pyc', '.bak', '.py~'],
'ignore_extensions': [],
'constructors': {},
}
parsers_by_directory = {}
# This is lazily initialized
init_module = NoDefault
def __init__(self, directory, base_python_name, add_options=None):
"""
Create a URLParser object that looks at `directory`.
`base_python_name` is the package that this directory
represents, thus any Python modules in this directory will
be given names under this package.
`add_options` overrides individual configuration options for
this instance.
"""
if os.path.sep != '/':
directory = directory.replace(os.path.sep, '/')
self.directory = directory
self.add_options = add_options
self.base_python_name = base_python_name
def __call__(self, environ, start_response):
environ['paste.urlparser.base_python_name'] = self.base_python_name
if self.add_options:
environ.setdefault('paste.urlparser.options', {}).update(
self.add_options)
if self.init_module is NoDefault:
self.init_module = self.find_init_module(environ)
path_info = environ.get('PATH_INFO', '')
if not path_info:
return self.add_slash(environ, start_response)
if (self.init_module
and getattr(self.init_module, 'urlparser_hook', None)):
self.init_module.urlparser_hook(environ)
orig_path_info = environ['PATH_INFO']
orig_script_name = environ['SCRIPT_NAME']
application, filename = self.find_application(environ)
if not application:
if (self.init_module
and getattr(self.init_module, 'not_found_hook', None)
and environ.get('paste.urlparser.not_found_parser') is not self):
not_found_hook = self.init_module.not_found_hook
environ['paste.urlparser.not_found_parser'] = self
environ['PATH_INFO'] = orig_path_info
environ['SCRIPT_NAME'] = orig_script_name
return not_found_hook(environ, start_response)
if filename is None:
name, rest_of_path = wsgilib.path_info_split(environ['PATH_INFO'])
if not name:
name = 'one of %s' % ', '.join(
self.option(environ, 'index_names') or
['(no index_names defined)'])
return self.not_found(
environ, start_response,
'Tried to load %s from directory %s'
% (name, self.directory))
else:
environ['wsgi.errors'].write(
'Found resource %s, but could not construct application\n'
% filename)
return self.not_found(
environ, start_response,
'Tried to load %s from directory %s'
% (filename, self.directory))
if (self.init_module
and getattr(self.init_module, 'urlparser_wrap', None)):
return self.init_module.urlparser_wrap(
environ, start_response, application)
else:
return application(environ, start_response)
def find_application(self, environ):
if (self.init_module
and getattr(self.init_module, 'application', None)
and not environ.get('paste.urlparser.init_application') == environ['SCRIPT_NAME']):
environ['paste.urlparser.init_application'] = environ['SCRIPT_NAME']
return self.init_module.application, None
name, rest_of_path = wsgilib.path_info_split(environ['PATH_INFO'])
environ['PATH_INFO'] = rest_of_path
if name is not None:
environ['SCRIPT_NAME'] = environ.get('SCRIPT_NAME', '') + '/' + name
if not name:
names = self.option(environ, 'index_names') or []
for index_name in names:
filename = self.find_file(environ, index_name)
if filename:
break
else:
# None of the index files found
filename = None
else:
filename = self.find_file(environ, name)
if filename is None:
return None, filename
else:
return self.get_application(environ, filename), filename
def not_found(self, environ, start_response, debug_message=None):
status, headers, body = wsgilib.error_response(
environ,
'404 Not Found',
'The resource at %s could not be found'
% wsgilib.construct_url(environ),
debug_message=debug_message)
start_response(status, headers)
return [body]
def option(self, environ, name):
return environ.get('paste.urlparser.options', {}).get(
name, self.default_options.get(name))
def add_slash(self, environ, start_response):
"""
This happens when you try to get to a directory
without a trailing /
"""
url = wsgilib.construct_url(environ, with_query_string=False)
url += '/'
if environ.get('QUERY_STRING'):
url += '?' + environ['QUERY_STRING']
status = '301 Moved Permanently'
status, headers, body = wsgilib.error_response(
environ,
status,
'''
<p>The resource has moved to <a href="%s">%s</a>. You
should be redirected automatically.</p>''' % (url, url))
start_response(status, headers + [('Location', url)])
return [body]
def find_file(self, environ, base_filename):
possible = []
"""Cache a few values to reduce function call overhead"""
ignore_extensions = self.option(environ, 'ignore_extensions')
hide_extensions = self.option(environ, 'hide_extensions')
for filename in os.listdir(self.directory):
base, ext = os.path.splitext(filename)
full_filename = os.path.join(self.directory, filename)
if (ext in hide_extensions
or not base):
continue
if filename == base_filename:
possible.append(full_filename)
continue
if ext in ignore_extensions:
continue
if base == base_filename:
possible.append(full_filename)
if not possible:
#environ['wsgi.errors'].write(
# 'No file found matching %r in %s\n'
# % (base_filename, self.directory))
return None
if len(possible) > 1:
environ['wsgi.errors'].write(
'Ambiguous URL: %s; matches files %s\n'
% (wsgilib.construct_url(environ),
', '.join(possible)))
return None
return possible[0]
def get_application(self, environ, filename):
constructors = self.option(environ, 'constructors')
if os.path.isdir(filename):
t = 'dir'
else:
t = os.path.splitext(filename)[1]
constructor = constructors.get(t, constructors.get('*'))
if constructor is None:
#environ['wsgi.errors'].write(
# 'No constructor found for %s\n' % t)
return constructor
app = constructor(environ, filename)
if app is None:
#environ['wsgi.errors'].write(
# 'Constructor %s return None for %s\n' %
# (constructor, filename))
pass
return app
def register_constructor(cls, extension, constructor):
"""
Register a function as a constructor. Registered constructors
apply to all instances of `URLParser`.
The extension should have a leading ``.``, or the special
extensions ``dir`` (for directories) and ``*`` (a catch-all).
`constructor` must be a callable that takes two arguments:
``environ`` and ``filename``, and returns a WSGI application.
"""
d = cls.default_options['constructors']
assert not d.has_key(extension), (
"A constructor already exists for the extension %r (%r) "
"when attemption to register constructor %r"
% (extension, d[extension], constructor))
d[extension] = constructor
register_constructor = classmethod(register_constructor)
def get_parser(cls, directory, base_python_name):
"""
Get a parser for the given directory, or create one if
necessary. This way parsers can be cached and reused.
"""
try:
return cls.parsers_by_directory[(directory, base_python_name)]
except KeyError:
parser = cls(directory, base_python_name)
cls.parsers_by_directory[(directory, base_python_name)] = parser
return parser
get_parser = classmethod(get_parser)
def find_init_module(self, environ):
filename = os.path.join(self.directory, '__init__.py')
if not os.path.exists(filename):
return None
return load_module(environ, filename)
def __repr__(self):
return '<%s directory=%r; module=%s at %s>' % (
self.__class__.__name__,
self.directory,
self.base_python_name,
hex(abs(id(self))))
def make_directory(environ, filename):
base_python_name = environ['paste.urlparser.base_python_name']
if base_python_name:
base_python_name += "." + os.path.basename(filename)
else:
base_python_name = os.path.basename(filename)
return URLParser.get_parser(filename, base_python_name)
URLParser.register_constructor('dir', make_directory)
def make_unknown(environ, filename):
return wsgilib.send_file(filename)
URLParser.register_constructor('*', make_unknown)
def load_module(environ, filename):
base_python_name = environ['paste.urlparser.base_python_name']
module_name = os.path.splitext(os.path.basename(filename))[0]
if base_python_name:
module_name = base_python_name + '.' + module_name
return load_module_from_name(environ, filename, module_name,
environ['wsgi.errors'])
def load_module_from_name(environ, filename, module_name, errors):
if sys.modules.has_key(module_name):
return sys.modules[module_name]
init_filename = os.path.join(os.path.dirname(filename), '__init__.py')
if not os.path.exists(init_filename):
try:
f = open(init_filename, 'w')
except (OSError, IOError), e:
errors.write(
'Cannot write __init__.py file into directory %s (%s)\n'
% (os.path.dirname(filename), e))
return None
f.write('#\n')
f.close()
fp = None
if sys.modules.has_key(module_name):
return sys.modules[module_name]
if '.' in module_name:
parent_name = '.'.join(module_name.split('.')[:-1])
base_name = module_name.split('.')[-1]
parent = load_module_from_name(environ, os.path.dirname(filename),
parent_name, errors)
else:
base_name = module_name
fp = None
try:
fp, pathname, stuff = imp.find_module(
base_name, [os.path.dirname(filename)])
module = imp.load_module(module_name, fp, pathname, stuff)
finally:
if fp is not None:
fp.close()
return module
def make_py(environ, filename):
module = load_module(environ, filename)
if not module:
return None
if hasattr(module, 'application') and module.application:
return module.application
base_name = module.__name__.split('.')[-1]
if hasattr(module, base_name):
return getattr(module, base_name)()
environ['wsgi.errors'].write(
"Cound not find application or %s in %s\n"
% (base_name, module))
return None
URLParser.register_constructor('.py', make_py)
class StaticURLParser(object):
"""
Like ``URLParser`` but only serves static files.
"""
# @@: Should URLParser subclass from this?
def __init__(self, directory):
if os.path.sep != '/':
directory = directory.replace(os.path.sep, '/')
self.directory = directory
def __call__(self, environ, start_response):
path_info = environ.get('PATH_INFO', '')
if not path_info:
return self.add_slash(environ, start_response)
if path_info == '/':
# @@: This should obviously be configurable
filename = 'index.html'
else:
filename = wsgilib.path_info_pop(environ)
full = os.path.join(self.directory, filename)
if not os.path.exists(full):
return self.not_found(environ, start_response)
if os.path.isdir(full):
# @@: Cache?
return self.__class__(full)(environ, start_response)
if environ.get('PATH_INFO') and environ.get('PATH_INFO') != '/':
return self.error_extra_path(environ, start_response)
return wsgilib.send_file(full)(environ, start_response)
def add_slash(self, environ, start_response):
"""
This happens when you try to get to a directory
without a trailing /
"""
url = wsgilib.construct_url(environ, with_query_string=False)
url += '/'
if environ.get('QUERY_STRING'):
url += '?' + environ['QUERY_STRING']
status = '301 Moved Permanently'
status, headers, body = wsgilib.error_response(
environ,
status,
'''
<p>The resource has moved to <a href="%s">%s</a>. You
should be redirected automatically.</p>''' % (url, url))
start_response(status, headers + [('Location', url)])
return [body]
def not_found(self, environ, start_response, debug_message=None):
status, headers, body = wsgilib.error_response(
environ,
'404 Not Found',
'The resource at %s could not be found'
% wsgilib.construct_url(environ),
debug_message=debug_message)
start_response(status, headers)
return [body]
def error_extra_path(self, environ, start_response):
status, headers, body = wsgilib.error_response(
environ,
'500 Bad Request',
'The trailing path %r is not allowed' % environ['PATH_INFO'])
start_response(status, headers)
return [body]
def __repr__(self):
return '<%s %r>' % (self.__class__.__name__, self.directory)
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