Mini Shell
"""Representing and manipulating email headers via custom objects.
This module provides an implementation of the HeaderRegistry API.
The implementation is designed to flexibly follow RFC5322 rules.
"""
from types import MappingProxyType
from email import utils
from email import errors
from email import _header_value_parser as parser
class Address:
def __init__(self, display_name='', username='', domain='', addr_spec=None):
"""Create an object representing a full email address.
An address can have a 'display_name', a 'username', and a 'domain'. In
addition to specifying the username and domain separately, they may be
specified together by using the addr_spec keyword *instead of* the
username and domain keywords. If an addr_spec string is specified it
must be properly quoted according to RFC 5322 rules; an error will be
raised if it is not.
An Address object has display_name, username, domain, and addr_spec
attributes, all of which are read-only. The addr_spec and the string
value of the object are both quoted according to RFC5322 rules, but
without any Content Transfer Encoding.
"""
inputs = ''.join(filter(None, (display_name, username, domain, addr_spec)))
if '\r' in inputs or '\n' in inputs:
raise ValueError("invalid arguments; address parts cannot contain CR or LF")
# This clause with its potential 'raise' may only happen when an
# application program creates an Address object using an addr_spec
# keyword. The email library code itself must always supply username
# and domain.
if addr_spec is not None:
if username or domain:
raise TypeError("addrspec specified when username and/or "
"domain also specified")
a_s, rest = parser.get_addr_spec(addr_spec)
if rest:
raise ValueError("Invalid addr_spec; only '{}' "
"could be parsed from '{}'".format(
a_s, addr_spec))
if a_s.all_defects:
raise a_s.all_defects[0]
username = a_s.local_part
domain = a_s.domain
self._display_name = display_name
self._username = username
self._domain = domain
@property
def display_name(self):
return self._display_name
@property
def username(self):
return self._username
@property
def domain(self):
return self._domain
@property
def addr_spec(self):
"""The addr_spec (username@domain) portion of the address, quoted
according to RFC 5322 rules, but with no Content Transfer Encoding.
"""
lp = self.username
if not parser.DOT_ATOM_ENDS.isdisjoint(lp):
lp = parser.quote_string(lp)
if self.domain:
return lp + '@' + self.domain
if not lp:
return '<>'
return lp
def __repr__(self):
return "{}(display_name={!r}, username={!r}, domain={!r})".format(
self.__class__.__name__,
self.display_name, self.username, self.domain)
def __str__(self):
disp = self.display_name
if not parser.SPECIALS.isdisjoint(disp):
disp = parser.quote_string(disp)
if disp:
addr_spec = '' if self.addr_spec=='<>' else self.addr_spec
return "{} <{}>".format(disp, addr_spec)
return self.addr_spec
def __eq__(self, other):
if not isinstance(other, Address):
return NotImplemented
return (self.display_name == other.display_name and
self.username == other.username and
self.domain == other.domain)
class Group:
def __init__(self, display_name=None, addresses=None):
"""Create an object representing an address group.
An address group consists of a display_name followed by colon and a
list of addresses (see Address) terminated by a semi-colon. The Group
is created by specifying a display_name and a possibly empty list of
Address objects. A Group can also be used to represent a single
address that is not in a group, which is convenient when manipulating
lists that are a combination of Groups and individual Addresses. In
this case the display_name should be set to None. In particular, the
string representation of a Group whose display_name is None is the same
as the Address object, if there is one and only one Address object in
the addresses list.
"""
self._display_name = display_name
self._addresses = tuple(addresses) if addresses else tuple()
@property
def display_name(self):
return self._display_name
@property
def addresses(self):
return self._addresses
def __repr__(self):
return "{}(display_name={!r}, addresses={!r}".format(
self.__class__.__name__,
self.display_name, self.addresses)
def __str__(self):
if self.display_name is None and len(self.addresses)==1:
return str(self.addresses[0])
disp = self.display_name
if disp is not None and not parser.SPECIALS.isdisjoint(disp):
disp = parser.quote_string(disp)
adrstr = ", ".join(str(x) for x in self.addresses)
adrstr = ' ' + adrstr if adrstr else adrstr
return "{}:{};".format(disp, adrstr)
def __eq__(self, other):
if not isinstance(other, Group):
return NotImplemented
return (self.display_name == other.display_name and
self.addresses == other.addresses)
# Header Classes #
class BaseHeader(str):
"""Base class for message headers.
Implements generic behavior and provides tools for subclasses.
A subclass must define a classmethod named 'parse' that takes an unfolded
value string and a dictionary as its arguments. The dictionary will
contain one key, 'defects', initialized to an empty list. After the call
the dictionary must contain two additional keys: parse_tree, set to the
parse tree obtained from parsing the header, and 'decoded', set to the
string value of the idealized representation of the data from the value.
(That is, encoded words are decoded, and values that have canonical
representations are so represented.)
The defects key is intended to collect parsing defects, which the message
parser will subsequently dispose of as appropriate. The parser should not,
insofar as practical, raise any errors. Defects should be added to the
list instead. The standard header parsers register defects for RFC
compliance issues, for obsolete RFC syntax, and for unrecoverable parsing
errors.
The parse method may add additional keys to the dictionary. In this case
the subclass must define an 'init' method, which will be passed the
dictionary as its keyword arguments. The method should use (usually by
setting them as the value of similarly named attributes) and remove all the
extra keys added by its parse method, and then use super to call its parent
class with the remaining arguments and keywords.
The subclass should also make sure that a 'max_count' attribute is defined
that is either None or 1. XXX: need to better define this API.
"""
def __new__(cls, name, value):
kwds = {'defects': []}
cls.parse(value, kwds)
if utils._has_surrogates(kwds['decoded']):
kwds['decoded'] = utils._sanitize(kwds['decoded'])
self = str.__new__(cls, kwds['decoded'])
del kwds['decoded']
self.init(name, **kwds)
return self
def init(self, name, *, parse_tree, defects):
self._name = name
self._parse_tree = parse_tree
self._defects = defects
@property
def name(self):
return self._name
@property
def defects(self):
return tuple(self._defects)
def __reduce__(self):
return (
_reconstruct_header,
(
self.__class__.__name__,
self.__class__.__bases__,
str(self),
),
self.__getstate__())
@classmethod
def _reconstruct(cls, value):
return str.__new__(cls, value)
def fold(self, *, policy):
"""Fold header according to policy.
The parsed representation of the header is folded according to
RFC5322 rules, as modified by the policy. If the parse tree
contains surrogateescaped bytes, the bytes are CTE encoded using
the charset 'unknown-8bit".
Any non-ASCII characters in the parse tree are CTE encoded using
charset utf-8. XXX: make this a policy setting.
The returned value is an ASCII-only string possibly containing linesep
characters, and ending with a linesep character. The string includes
the header name and the ': ' separator.
"""
# At some point we need to put fws here if it was in the source.
header = parser.Header([
parser.HeaderLabel([
parser.ValueTerminal(self.name, 'header-name'),
parser.ValueTerminal(':', 'header-sep')]),
])
if self._parse_tree:
header.append(
parser.CFWSList([parser.WhiteSpaceTerminal(' ', 'fws')]))
header.append(self._parse_tree)
return header.fold(policy=policy)
def _reconstruct_header(cls_name, bases, value):
return type(cls_name, bases, {})._reconstruct(value)
class UnstructuredHeader:
max_count = None
value_parser = staticmethod(parser.get_unstructured)
@classmethod
def parse(cls, value, kwds):
kwds['parse_tree'] = cls.value_parser(value)
kwds['decoded'] = str(kwds['parse_tree'])
class UniqueUnstructuredHeader(UnstructuredHeader):
max_count = 1
class DateHeader:
"""Header whose value consists of a single timestamp.
Provides an additional attribute, datetime, which is either an aware
datetime using a timezone, or a naive datetime if the timezone
in the input string is -0000. Also accepts a datetime as input.
The 'value' attribute is the normalized form of the timestamp,
which means it is the output of format_datetime on the datetime.
"""
max_count = None
# This is used only for folding, not for creating 'decoded'.
value_parser = staticmethod(parser.get_unstructured)
@classmethod
def parse(cls, value, kwds):
if not value:
kwds['defects'].append(errors.HeaderMissingRequiredValue())
kwds['datetime'] = None
kwds['decoded'] = ''
kwds['parse_tree'] = parser.TokenList()
return
if isinstance(value, str):
kwds['decoded'] = value
try:
value = utils.parsedate_to_datetime(value)
except ValueError:
kwds['defects'].append(errors.InvalidDateDefect('Invalid date value or format'))
kwds['datetime'] = None
kwds['parse_tree'] = parser.TokenList()
return
kwds['datetime'] = value
kwds['decoded'] = utils.format_datetime(kwds['datetime'])
kwds['parse_tree'] = cls.value_parser(kwds['decoded'])
def init(self, *args, **kw):
self._datetime = kw.pop('datetime')
super().init(*args, **kw)
@property
def datetime(self):
return self._datetime
class UniqueDateHeader(DateHeader):
max_count = 1
class AddressHeader:
max_count = None
@staticmethod
def value_parser(value):
address_list, value = parser.get_address_list(value)
assert not value, 'this should not happen'
return address_list
@classmethod
def parse(cls, value, kwds):
if isinstance(value, str):
# We are translating here from the RFC language (address/mailbox)
# to our API language (group/address).
kwds['parse_tree'] = address_list = cls.value_parser(value)
groups = []
for addr in address_list.addresses:
groups.append(Group(addr.display_name,
[Address(mb.display_name or '',
mb.local_part or '',
mb.domain or '')
for mb in addr.all_mailboxes]))
defects = list(address_list.all_defects)
else:
# Assume it is Address/Group stuff
if not hasattr(value, '__iter__'):
value = [value]
groups = [Group(None, [item]) if not hasattr(item, 'addresses')
else item
for item in value]
defects = []
kwds['groups'] = groups
kwds['defects'] = defects
kwds['decoded'] = ', '.join([str(item) for item in groups])
if 'parse_tree' not in kwds:
kwds['parse_tree'] = cls.value_parser(kwds['decoded'])
def init(self, *args, **kw):
self._groups = tuple(kw.pop('groups'))
self._addresses = None
super().init(*args, **kw)
@property
def groups(self):
return self._groups
@property
def addresses(self):
if self._addresses is None:
self._addresses = tuple(address for group in self._groups
for address in group.addresses)
return self._addresses
class UniqueAddressHeader(AddressHeader):
max_count = 1
class SingleAddressHeader(AddressHeader):
@property
def address(self):
if len(self.addresses)!=1:
raise ValueError(("value of single address header {} is not "
"a single address").format(self.name))
return self.addresses[0]
class UniqueSingleAddressHeader(SingleAddressHeader):
max_count = 1
class MIMEVersionHeader:
max_count = 1
value_parser = staticmethod(parser.parse_mime_version)
@classmethod
def parse(cls, value, kwds):
kwds['parse_tree'] = parse_tree = cls.value_parser(value)
kwds['decoded'] = str(parse_tree)
kwds['defects'].extend(parse_tree.all_defects)
kwds['major'] = None if parse_tree.minor is None else parse_tree.major
kwds['minor'] = parse_tree.minor
if parse_tree.minor is not None:
kwds['version'] = '{}.{}'.format(kwds['major'], kwds['minor'])
else:
kwds['version'] = None
def init(self, *args, **kw):
self._version = kw.pop('version')
self._major = kw.pop('major')
self._minor = kw.pop('minor')
super().init(*args, **kw)
@property
def major(self):
return self._major
@property
def minor(self):
return self._minor
@property
def version(self):
return self._version
class ParameterizedMIMEHeader:
# Mixin that handles the params dict. Must be subclassed and
# a property value_parser for the specific header provided.
max_count = 1
@classmethod
def parse(cls, value, kwds):
kwds['parse_tree'] = parse_tree = cls.value_parser(value)
kwds['decoded'] = str(parse_tree)
kwds['defects'].extend(parse_tree.all_defects)
if parse_tree.params is None:
kwds['params'] = {}
else:
# The MIME RFCs specify that parameter ordering is arbitrary.
kwds['params'] = {utils._sanitize(name).lower():
utils._sanitize(value)
for name, value in parse_tree.params}
def init(self, *args, **kw):
self._params = kw.pop('params')
super().init(*args, **kw)
@property
def params(self):
return MappingProxyType(self._params)
class ContentTypeHeader(ParameterizedMIMEHeader):
value_parser = staticmethod(parser.parse_content_type_header)
def init(self, *args, **kw):
super().init(*args, **kw)
self._maintype = utils._sanitize(self._parse_tree.maintype)
self._subtype = utils._sanitize(self._parse_tree.subtype)
@property
def maintype(self):
return self._maintype
@property
def subtype(self):
return self._subtype
@property
def content_type(self):
return self.maintype + '/' + self.subtype
class ContentDispositionHeader(ParameterizedMIMEHeader):
value_parser = staticmethod(parser.parse_content_disposition_header)
def init(self, *args, **kw):
super().init(*args, **kw)
cd = self._parse_tree.content_disposition
self._content_disposition = cd if cd is None else utils._sanitize(cd)
@property
def content_disposition(self):
return self._content_disposition
class ContentTransferEncodingHeader:
max_count = 1
value_parser = staticmethod(parser.parse_content_transfer_encoding_header)
@classmethod
def parse(cls, value, kwds):
kwds['parse_tree'] = parse_tree = cls.value_parser(value)
kwds['decoded'] = str(parse_tree)
kwds['defects'].extend(parse_tree.all_defects)
def init(self, *args, **kw):
super().init(*args, **kw)
self._cte = utils._sanitize(self._parse_tree.cte)
@property
def cte(self):
return self._cte
class MessageIDHeader:
max_count = 1
value_parser = staticmethod(parser.parse_message_id)
@classmethod
def parse(cls, value, kwds):
kwds['parse_tree'] = parse_tree = cls.value_parser(value)
kwds['decoded'] = str(parse_tree)
kwds['defects'].extend(parse_tree.all_defects)
# The header factory #
_default_header_map = {
'subject': UniqueUnstructuredHeader,
'date': UniqueDateHeader,
'resent-date': DateHeader,
'orig-date': UniqueDateHeader,
'sender': UniqueSingleAddressHeader,
'resent-sender': SingleAddressHeader,
'to': UniqueAddressHeader,
'resent-to': AddressHeader,
'cc': UniqueAddressHeader,
'resent-cc': AddressHeader,
'bcc': UniqueAddressHeader,
'resent-bcc': AddressHeader,
'from': UniqueAddressHeader,
'resent-from': AddressHeader,
'reply-to': UniqueAddressHeader,
'mime-version': MIMEVersionHeader,
'content-type': ContentTypeHeader,
'content-disposition': ContentDispositionHeader,
'content-transfer-encoding': ContentTransferEncodingHeader,
'message-id': MessageIDHeader,
}
class HeaderRegistry:
"""A header_factory and header registry."""
def __init__(self, base_class=BaseHeader, default_class=UnstructuredHeader,
use_default_map=True):
"""Create a header_factory that works with the Policy API.
base_class is the class that will be the last class in the created
header class's __bases__ list. default_class is the class that will be
used if "name" (see __call__) does not appear in the registry.
use_default_map controls whether or not the default mapping of names to
specialized classes is copied in to the registry when the factory is
created. The default is True.
"""
self.registry = {}
self.base_class = base_class
self.default_class = default_class
if use_default_map:
self.registry.update(_default_header_map)
def map_to_type(self, name, cls):
"""Register cls as the specialized class for handling "name" headers.
"""
self.registry[name.lower()] = cls
def __getitem__(self, name):
cls = self.registry.get(name.lower(), self.default_class)
return type('_'+cls.__name__, (cls, self.base_class), {})
def __call__(self, name, value):
"""Create a header instance for header 'name' from 'value'.
Creates a header instance by creating a specialized class for parsing
and representing the specified header by combining the factory
base_class with a specialized class from the registry or the
default_class, and passing the name and value to the constructed
class's constructor.
"""
return self[name](name, value)
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