# Django 2.2.9.dev20191202104323 文档

# django.core.mail.message 源代码

    import mimetypes
    from email import (
        charset as Charset, encoders as Encoders, generator, message_from_string,
    )
    from email.errors import InvalidHeaderDefect, NonASCIILocalPartDefect
    from email.header import Header
    from email.headerregistry import Address
    from email.message import Message
    from email.mime.base import MIMEBase
    from email.mime.message import MIMEMessage
    from email.mime.multipart import MIMEMultipart
    from email.mime.text import MIMEText
    from email.utils import formatdate, getaddresses, make_msgid, parseaddr
    from io import BytesIO, StringIO
    from pathlib import Path

    from django.conf import settings
    from django.core.mail.utils import DNS_NAME
    from django.utils.encoding import force_text

    # Don't BASE64-encode UTF-8 messages so that we avoid unwanted attention from
    # some spam filters.
    utf8_charset = Charset.Charset('utf-8')
    utf8_charset.body_encoding = None  # Python defaults to BASE64
    utf8_charset_qp = Charset.Charset('utf-8')
    utf8_charset_qp.body_encoding = Charset.QP

    # Default MIME type to use on attachments (if it is not explicitly given
    # and cannot be guessed).
    DEFAULT_ATTACHMENT_MIME_TYPE = 'application/octet-stream'

    RFC5322_EMAIL_LINE_LENGTH_LIMIT = 998

    class BadHeaderError(ValueError):
        pass

    # Header names that contain structured address data (RFC #5322)
    ADDRESS_HEADERS = {
        'from',
        'sender',
        'reply-to',
        'to',
        'cc',
        'bcc',
        'resent-from',
        'resent-sender',
        'resent-to',
        'resent-cc',
        'resent-bcc',
    }

    def forbid_multi_line_headers(name, val, encoding):
        """Forbid multi-line headers to prevent header injection."""
        encoding = encoding or settings.DEFAULT_CHARSET
        val = str(val)  # val may be lazy
        if '\n' in val or '\r' in val:
            raise BadHeaderError("Header values can't contain newlines (got %r for header %r)" % (val, name))
        try:
            val.encode('ascii')
        except UnicodeEncodeError:
            if name.lower() in ADDRESS_HEADERS:
                val = ', '.join(sanitize_address(addr, encoding) for addr in getaddresses((val,)))
            else:
                val = Header(val, encoding).encode()
        else:
            if name.lower() == 'subject':
                val = Header(val).encode()
        return name, val

    def split_addr(addr, encoding):
        """
        Split the address into local part and domain and encode them.

        When non-ascii characters are present in the local part, it must be
        MIME-word encoded. The domain name must be idna-encoded if it contains
        non-ascii characters.
        """
        if '@' in addr:
            localpart, domain = addr.split('@', 1)
            # Try to get the simplest encoding - ascii if possible so that
            # to@example.com doesn't become =?utf-8?q?to?=@example.com. This
            # makes unit testing a bit easier and more readable.
            try:
                localpart.encode('ascii')
            except UnicodeEncodeError:
                localpart = Header(localpart, encoding).encode()
            domain = domain.encode('idna').decode('ascii')
        else:
            localpart = Header(addr, encoding).encode()
            domain = ''
        return (localpart, domain)

    def sanitize_address(addr, encoding):
        """
        Format a pair of (name, address) or an email address string.
        """
        if not isinstance(addr, tuple):
            addr = parseaddr(addr)
        nm, addr = addr
        localpart, domain = None, None
        nm = Header(nm, encoding).encode()
        try:
            addr.encode('ascii')
        except UnicodeEncodeError:  # IDN or non-ascii in the local part
            localpart, domain = split_addr(addr, encoding)

        # An `email.headerregistry.Address` object is used since
        # email.utils.formataddr() naively encodes the name as ascii (see #25986).
        if localpart and domain:
            address = Address(nm, username=localpart, domain=domain)
            return str(address)

        try:
            address = Address(nm, addr_spec=addr)
        except (InvalidHeaderDefect, NonASCIILocalPartDefect):
            localpart, domain = split_addr(addr, encoding)
            address = Address(nm, username=localpart, domain=domain)
        return str(address)

    class MIMEMixin:
        def as_string(self, unixfrom=False, linesep='\n'):
            """Return the entire formatted message as a string.
            Optional `unixfrom' when True, means include the Unix From_ envelope
            header.

            This overrides the default as_string() implementation to not mangle
            lines that begin with 'From '. See bug #13433 for details.
            """
            fp = StringIO()
            g = generator.Generator(fp, mangle_from_=False)
            g.flatten(self, unixfrom=unixfrom, linesep=linesep)
            return fp.getvalue()

        def as_bytes(self, unixfrom=False, linesep='\n'):
            """Return the entire formatted message as bytes.
            Optional `unixfrom' when True, means include the Unix From_ envelope
            header.

            This overrides the default as_bytes() implementation to not mangle
            lines that begin with 'From '. See bug #13433 for details.
            """
            fp = BytesIO()
            g = generator.BytesGenerator(fp, mangle_from_=False)
            g.flatten(self, unixfrom=unixfrom, linesep=linesep)
            return fp.getvalue()

    class SafeMIMEMessage(MIMEMixin, MIMEMessage):

        def __setitem__(self, name, val):
            # message/rfc822 attachments must be ASCII
            name, val = forbid_multi_line_headers(name, val, 'ascii')
            MIMEMessage.__setitem__(self, name, val)

    class SafeMIMEText(MIMEMixin, MIMEText):

        def __init__(self, _text, _subtype='plain', _charset=None):
            self.encoding = _charset
            MIMEText.__init__(self, _text, _subtype=_subtype, _charset=_charset)

        def __setitem__(self, name, val):
            name, val = forbid_multi_line_headers(name, val, self.encoding)
            MIMEText.__setitem__(self, name, val)

        def set_payload(self, payload, charset=None):
            if charset == 'utf-8' and not isinstance(charset, Charset.Charset):
                has_long_lines = any(
                    len(l.encode()) > RFC5322_EMAIL_LINE_LENGTH_LIMIT
                    for l in payload.splitlines()
                )
                # Quoted-Printable encoding has the side effect of shortening long
                # lines, if any (#22561).
                charset = utf8_charset_qp if has_long_lines else utf8_charset
            MIMEText.set_payload(self, payload, charset=charset)

    class SafeMIMEMultipart(MIMEMixin, MIMEMultipart):

        def __init__(self, _subtype='mixed', boundary=None, _subparts=None, encoding=None, **_params):
            self.encoding = encoding
            MIMEMultipart.__init__(self, _subtype, boundary, _subparts, **_params)

        def __setitem__(self, name, val):
            name, val = forbid_multi_line_headers(name, val, self.encoding)
            MIMEMultipart.__setitem__(self, name, val)

    class EmailMessage:
        """A container for email information."""
        content_subtype = 'plain'
        mixed_subtype = 'mixed'
        encoding = None     # None => use settings default

        def __init__(self, subject='', body='', from_email=None, to=None, bcc=None,
                     connection=None, attachments=None, headers=None, cc=None,
                     reply_to=None):
            """
            Initialize a single email message (which can be sent to multiple
            recipients).
            """
            if to:
                if isinstance(to, str):
                    raise TypeError('"to" argument must be a list or tuple')
                self.to = list(to)
            else:
                self.to = []
            if cc:
                if isinstance(cc, str):
                    raise TypeError('"cc" argument must be a list or tuple')
                self.cc = list(cc)
            else:
                self.cc = []
            if bcc:
                if isinstance(bcc, str):
                    raise TypeError('"bcc" argument must be a list or tuple')
                self.bcc = list(bcc)
            else:
                self.bcc = []
            if reply_to:
                if isinstance(reply_to, str):
                    raise TypeError('"reply_to" argument must be a list or tuple')
                self.reply_to = list(reply_to)
            else:
                self.reply_to = []
            self.from_email = from_email or settings.DEFAULT_FROM_EMAIL
            self.subject = subject
            self.body = body or ''
            self.attachments = []
            if attachments:
                for attachment in attachments:
                    if isinstance(attachment, MIMEBase):
                        self.attach(attachment)
                    else:
                        self.attach(*attachment)
            self.extra_headers = headers or {}
            self.connection = connection

        def get_connection(self, fail_silently=False):
            from django.core.mail import get_connection
            if not self.connection:
                self.connection = get_connection(fail_silently=fail_silently)
            return self.connection

        def message(self):
            encoding = self.encoding or settings.DEFAULT_CHARSET
            msg = SafeMIMEText(self.body, self.content_subtype, encoding)
            msg = self._create_message(msg)
            msg['Subject'] = self.subject
            msg['From'] = self.extra_headers.get('From', self.from_email)
            self._set_list_header_if_not_empty(msg, 'To', self.to)
            self._set_list_header_if_not_empty(msg, 'Cc', self.cc)
            self._set_list_header_if_not_empty(msg, 'Reply-To', self.reply_to)

            # Email header names are case-insensitive (RFC 2045), so we have to
            # accommodate that when doing comparisons.
            header_names = [key.lower() for key in self.extra_headers]
            if 'date' not in header_names:
                # formatdate() uses stdlib methods to format the date, which use
                # the stdlib/OS concept of a timezone, however, Django sets the
                # TZ environment variable based on the TIME_ZONE setting which
                # will get picked up by formatdate().
                msg['Date'] = formatdate(localtime=settings.EMAIL_USE_LOCALTIME)
            if 'message-id' not in header_names:
                # Use cached DNS_NAME for performance
                msg['Message-ID'] = make_msgid(domain=DNS_NAME)
            for name, value in self.extra_headers.items():
                if name.lower() != 'from':  # From is already handled
                    msg[name] = value
            return msg

        def recipients(self):
            """
            Return a list of all recipients of the email (includes direct
            addressees as well as Cc and Bcc entries).
            """
            return [email for email in (self.to + self.cc + self.bcc) if email]

        def send(self, fail_silently=False):
            """Send the email message."""
            if not self.recipients():
                # Don't bother creating the network connection if there's nobody to
                # send to.
                return 0
            return self.get_connection(fail_silently).send_messages([self])

        def attach(self, filename=None, content=None, mimetype=None):
            """
            Attach a file with the given filename and content. The filename can
            be omitted and the mimetype is guessed, if not provided.

            If the first parameter is a MIMEBase subclass, insert it directly
            into the resulting message attachments.

            For a text/* mimetype (guessed or specified), when a bytes object is
            specified as content, decode it as UTF-8. If that fails, set the
            mimetype to DEFAULT_ATTACHMENT_MIME_TYPE and don't decode the content.
            """
            if isinstance(filename, MIMEBase):
                assert content is None
                assert mimetype is None
                self.attachments.append(filename)
            else:
                assert content is not None
                mimetype = mimetype or mimetypes.guess_type(filename)[0] or DEFAULT_ATTACHMENT_MIME_TYPE
                basetype, subtype = mimetype.split('/', 1)

                if basetype == 'text':
                    if isinstance(content, bytes):
                        try:
                            content = content.decode()
                        except UnicodeDecodeError:
                            # If mimetype suggests the file is text but it's
                            # actually binary, read() raises a UnicodeDecodeError.
                            mimetype = DEFAULT_ATTACHMENT_MIME_TYPE

                self.attachments.append((filename, content, mimetype))

        def attach_file(self, path, mimetype=None):
            """
            Attach a file from the filesystem.

            Set the mimetype to DEFAULT_ATTACHMENT_MIME_TYPE if it isn't specified
            and cannot be guessed.

            For a text/* mimetype (guessed or specified), decode the file's content
            as UTF-8. If that fails, set the mimetype to
            DEFAULT_ATTACHMENT_MIME_TYPE and don't decode the content.
            """
            path = Path(path)
            with path.open('rb') as file:
                content = file.read()
                self.attach(path.name, content, mimetype)

        def _create_message(self, msg):
            return self._create_attachments(msg)

        def _create_attachments(self, msg):
            if self.attachments:
                encoding = self.encoding or settings.DEFAULT_CHARSET
                body_msg = msg
                msg = SafeMIMEMultipart(_subtype=self.mixed_subtype, encoding=encoding)
                if self.body or body_msg.is_multipart():
                    msg.attach(body_msg)
                for attachment in self.attachments:
                    if isinstance(attachment, MIMEBase):
                        msg.attach(attachment)
                    else:
                        msg.attach(self._create_attachment(*attachment))
            return msg

        def _create_mime_attachment(self, content, mimetype):
            """
            Convert the content, mimetype pair into a MIME attachment object.

            If the mimetype is message/rfc822, content may be an
            email.Message or EmailMessage object, as well as a str.
            """
            basetype, subtype = mimetype.split('/', 1)
            if basetype == 'text':
                encoding = self.encoding or settings.DEFAULT_CHARSET
                attachment = SafeMIMEText(content, subtype, encoding)
            elif basetype == 'message' and subtype == 'rfc822':
                # Bug #18967: per RFC2046 s5.2.1, message/rfc822 attachments
                # must not be base64 encoded.
                if isinstance(content, EmailMessage):
                    # convert content into an email.Message first
                    content = content.message()
                elif not isinstance(content, Message):
                    # For compatibility with existing code, parse the message
                    # into an email.Message object if it is not one already.
                    content = message_from_string(force_text(content))

                attachment = SafeMIMEMessage(content, subtype)
            else:
                # Encode non-text attachments with base64.
                attachment = MIMEBase(basetype, subtype)
                attachment.set_payload(content)
                Encoders.encode_base64(attachment)
            return attachment

        def _create_attachment(self, filename, content, mimetype=None):
            """
            Convert the filename, content, mimetype triple into a MIME attachment
            object.
            """
            attachment = self._create_mime_attachment(content, mimetype)
            if filename:
                try:
                    filename.encode('ascii')
                except UnicodeEncodeError:
                    filename = ('utf-8', '', filename)
                attachment.add_header('Content-Disposition', 'attachment', filename=filename)
            return attachment

        def _set_list_header_if_not_empty(self, msg, header, values):
            """
            Set msg's header, either from self.extra_headers, if present, or from
            the values argument.
            """
            if values:
                try:
                    value = self.extra_headers[header]
                except KeyError:
                    value = ', '.join(str(v) for v in values)
                msg[header] = value

    class EmailMultiAlternatives(EmailMessage):
        """
        A version of EmailMessage that makes it easy to send multipart/alternative
        messages. For example, including text and HTML versions of the text is
        made easier.
        """
        alternative_subtype = 'alternative'

        def __init__(self, subject='', body='', from_email=None, to=None, bcc=None,
                     connection=None, attachments=None, headers=None, alternatives=None,
                     cc=None, reply_to=None):
            """
            Initialize a single email message (which can be sent to multiple
            recipients).
            """
            super().__init__(
                subject, body, from_email, to, bcc, connection, attachments,
                headers, cc, reply_to,
            )
            self.alternatives = alternatives or []

        def attach_alternative(self, content, mimetype):
            """Attach an alternative content representation."""
            assert content is not None
            assert mimetype is not None
            self.alternatives.append((content, mimetype))

        def _create_message(self, msg):
            return self._create_attachments(self._create_alternatives(msg))

        def _create_alternatives(self, msg):
            encoding = self.encoding or settings.DEFAULT_CHARSET
            if self.alternatives:
                body_msg = msg
                msg = SafeMIMEMultipart(_subtype=self.alternative_subtype, encoding=encoding)
                if self.body:
                    msg.attach(body_msg)
                for alternative in self.alternatives:
                    msg.attach(self._create_mime_attachment(*alternative))
            return msg