Add future 0.18.2

lib/future/backports/email/generator.py

@@ -0,0 +1,498 @@
+# Copyright (C) 2001-2010 Python Software Foundation
+# Author: Barry Warsaw
+# Contact: email-sig@python.org
+
+"""Classes to generate plain text from a message object tree."""
+from __future__ import print_function
+from __future__ import unicode_literals
+from __future__ import division
+from __future__ import absolute_import
+from future.builtins import super
+from future.builtins import str
+
+__all__ = ['Generator', 'DecodedGenerator', 'BytesGenerator']
+
+import re
+import sys
+import time
+import random
+import warnings
+
+from io import StringIO, BytesIO
+from future.backports.email._policybase import compat32
+from future.backports.email.header import Header
+from future.backports.email.utils import _has_surrogates
+import future.backports.email.charset as _charset
+
+UNDERSCORE = '_'
+NL = '\n'  # XXX: no longer used by the code below.
+
+fcre = re.compile(r'^From ', re.MULTILINE)
+
+
+class Generator(object):
+    """Generates output from a Message object tree.
+
+    This basic generator writes the message to the given file object as plain
+    text.
+    """
+    #
+    # Public interface
+    #
+
+    def __init__(self, outfp, mangle_from_=True, maxheaderlen=None, **_3to2kwargs):
+        if 'policy' in _3to2kwargs: policy = _3to2kwargs['policy']; del _3to2kwargs['policy']
+        else: policy = None
+        """Create the generator for message flattening.
+
+        outfp is the output file-like object for writing the message to.  It
+        must have a write() method.
+
+        Optional mangle_from_ is a flag that, when True (the default), escapes
+        From_ lines in the body of the message by putting a `>' in front of
+        them.
+
+        Optional maxheaderlen specifies the longest length for a non-continued
+        header.  When a header line is longer (in characters, with tabs
+        expanded to 8 spaces) than maxheaderlen, the header will split as
+        defined in the Header class.  Set maxheaderlen to zero to disable
+        header wrapping.  The default is 78, as recommended (but not required)
+        by RFC 2822.
+
+        The policy keyword specifies a policy object that controls a number of
+        aspects of the generator's operation.  The default policy maintains
+        backward compatibility.
+
+        """
+        self._fp = outfp
+        self._mangle_from_ = mangle_from_
+        self.maxheaderlen = maxheaderlen
+        self.policy = policy
+
+    def write(self, s):
+        # Just delegate to the file object
+        self._fp.write(s)
+
+    def flatten(self, msg, unixfrom=False, linesep=None):
+        r"""Print the message object tree rooted at msg to the output file
+        specified when the Generator instance was created.
+
+        unixfrom is a flag that forces the printing of a Unix From_ delimiter
+        before the first object in the message tree.  If the original message
+        has no From_ delimiter, a `standard' one is crafted.  By default, this
+        is False to inhibit the printing of any From_ delimiter.
+
+        Note that for subobjects, no From_ line is printed.
+
+        linesep specifies the characters used to indicate a new line in
+        the output.  The default value is determined by the policy.
+
+        """
+        # We use the _XXX constants for operating on data that comes directly
+        # from the msg, and _encoded_XXX constants for operating on data that
+        # has already been converted (to bytes in the BytesGenerator) and
+        # inserted into a temporary buffer.
+        policy = msg.policy if self.policy is None else self.policy
+        if linesep is not None:
+            policy = policy.clone(linesep=linesep)
+        if self.maxheaderlen is not None:
+            policy = policy.clone(max_line_length=self.maxheaderlen)
+        self._NL = policy.linesep
+        self._encoded_NL = self._encode(self._NL)
+        self._EMPTY = ''
+        self._encoded_EMTPY = self._encode('')
+        # Because we use clone (below) when we recursively process message
+        # subparts, and because clone uses the computed policy (not None),
+        # submessages will automatically get set to the computed policy when
+        # they are processed by this code.
+        old_gen_policy = self.policy
+        old_msg_policy = msg.policy
+        try:
+            self.policy = policy
+            msg.policy = policy
+            if unixfrom:
+                ufrom = msg.get_unixfrom()
+                if not ufrom:
+                    ufrom = 'From nobody ' + time.ctime(time.time())
+                self.write(ufrom + self._NL)
+            self._write(msg)
+        finally:
+            self.policy = old_gen_policy
+            msg.policy = old_msg_policy
+
+    def clone(self, fp):
+        """Clone this generator with the exact same options."""
+        return self.__class__(fp,
+                              self._mangle_from_,
+                              None, # Use policy setting, which we've adjusted
+                              policy=self.policy)
+
+    #
+    # Protected interface - undocumented ;/
+    #
+
+    # Note that we use 'self.write' when what we are writing is coming from
+    # the source, and self._fp.write when what we are writing is coming from a
+    # buffer (because the Bytes subclass has already had a chance to transform
+    # the data in its write method in that case).  This is an entirely
+    # pragmatic split determined by experiment; we could be more general by
+    # always using write and having the Bytes subclass write method detect when
+    # it has already transformed the input; but, since this whole thing is a
+    # hack anyway this seems good enough.
+
+    # Similarly, we have _XXX and _encoded_XXX attributes that are used on
+    # source and buffer data, respectively.
+    _encoded_EMPTY = ''
+
+    def _new_buffer(self):
+        # BytesGenerator overrides this to return BytesIO.
+        return StringIO()
+
+    def _encode(self, s):
+        # BytesGenerator overrides this to encode strings to bytes.
+        return s
+
+    def _write_lines(self, lines):
+        # We have to transform the line endings.
+        if not lines:
+            return
+        lines = lines.splitlines(True)
+        for line in lines[:-1]:
+            self.write(line.rstrip('\r\n'))
+            self.write(self._NL)
+        laststripped = lines[-1].rstrip('\r\n')
+        self.write(laststripped)
+        if len(lines[-1]) != len(laststripped):
+            self.write(self._NL)
+
+    def _write(self, msg):
+        # We can't write the headers yet because of the following scenario:
+        # say a multipart message includes the boundary string somewhere in
+        # its body.  We'd have to calculate the new boundary /before/ we write
+        # the headers so that we can write the correct Content-Type:
+        # parameter.
+        #
+        # The way we do this, so as to make the _handle_*() methods simpler,
+        # is to cache any subpart writes into a buffer.  The we write the
+        # headers and the buffer contents.  That way, subpart handlers can
+        # Do The Right Thing, and can still modify the Content-Type: header if
+        # necessary.
+        oldfp = self._fp
+        try:
+            self._fp = sfp = self._new_buffer()
+            self._dispatch(msg)
+        finally:
+            self._fp = oldfp
+        # Write the headers.  First we see if the message object wants to
+        # handle that itself.  If not, we'll do it generically.
+        meth = getattr(msg, '_write_headers', None)
+        if meth is None:
+            self._write_headers(msg)
+        else:
+            meth(self)
+        self._fp.write(sfp.getvalue())
+
+    def _dispatch(self, msg):
+        # Get the Content-Type: for the message, then try to dispatch to
+        # self._handle_<maintype>_<subtype>().  If there's no handler for the
+        # full MIME type, then dispatch to self._handle_<maintype>().  If
+        # that's missing too, then dispatch to self._writeBody().
+        main = msg.get_content_maintype()
+        sub = msg.get_content_subtype()
+        specific = UNDERSCORE.join((main, sub)).replace('-', '_')
+        meth = getattr(self, '_handle_' + specific, None)
+        if meth is None:
+            generic = main.replace('-', '_')
+            meth = getattr(self, '_handle_' + generic, None)
+            if meth is None:
+                meth = self._writeBody
+        meth(msg)
+
+    #
+    # Default handlers
+    #
+
+    def _write_headers(self, msg):
+        for h, v in msg.raw_items():
+            self.write(self.policy.fold(h, v))
+        # A blank line always separates headers from body
+        self.write(self._NL)
+
+    #
+    # Handlers for writing types and subtypes
+    #
+
+    def _handle_text(self, msg):
+        payload = msg.get_payload()
+        if payload is None:
+            return
+        if not isinstance(payload, str):
+            raise TypeError('string payload expected: %s' % type(payload))
+        if _has_surrogates(msg._payload):
+            charset = msg.get_param('charset')
+            if charset is not None:
+                del msg['content-transfer-encoding']
+                msg.set_payload(payload, charset)
+                payload = msg.get_payload()
+        if self._mangle_from_:
+            payload = fcre.sub('>From ', payload)
+        self._write_lines(payload)
+
+    # Default body handler
+    _writeBody = _handle_text
+
+    def _handle_multipart(self, msg):
+        # The trick here is to write out each part separately, merge them all
+        # together, and then make sure that the boundary we've chosen isn't
+        # present in the payload.
+        msgtexts = []
+        subparts = msg.get_payload()
+        if subparts is None:
+            subparts = []
+        elif isinstance(subparts, str):
+            # e.g. a non-strict parse of a message with no starting boundary.
+            self.write(subparts)
+            return
+        elif not isinstance(subparts, list):
+            # Scalar payload
+            subparts = [subparts]
+        for part in subparts:
+            s = self._new_buffer()
+            g = self.clone(s)
+            g.flatten(part, unixfrom=False, linesep=self._NL)
+            msgtexts.append(s.getvalue())
+        # BAW: What about boundaries that are wrapped in double-quotes?
+        boundary = msg.get_boundary()
+        if not boundary:
+            # Create a boundary that doesn't appear in any of the
+            # message texts.
+            alltext = self._encoded_NL.join(msgtexts)
+            boundary = self._make_boundary(alltext)
+            msg.set_boundary(boundary)
+        # If there's a preamble, write it out, with a trailing CRLF
+        if msg.preamble is not None:
+            if self._mangle_from_:
+                preamble = fcre.sub('>From ', msg.preamble)
+            else:
+                preamble = msg.preamble
+            self._write_lines(preamble)
+            self.write(self._NL)
+        # dash-boundary transport-padding CRLF
+        self.write('--' + boundary + self._NL)
+        # body-part
+        if msgtexts:
+            self._fp.write(msgtexts.pop(0))
+        # *encapsulation
+        # --> delimiter transport-padding
+        # --> CRLF body-part
+        for body_part in msgtexts:
+            # delimiter transport-padding CRLF
+            self.write(self._NL + '--' + boundary + self._NL)
+            # body-part
+            self._fp.write(body_part)
+        # close-delimiter transport-padding
+        self.write(self._NL + '--' + boundary + '--')
+        if msg.epilogue is not None:
+            self.write(self._NL)
+            if self._mangle_from_:
+                epilogue = fcre.sub('>From ', msg.epilogue)
+            else:
+                epilogue = msg.epilogue
+            self._write_lines(epilogue)
+
+    def _handle_multipart_signed(self, msg):
+        # The contents of signed parts has to stay unmodified in order to keep
+        # the signature intact per RFC1847 2.1, so we disable header wrapping.
+        # RDM: This isn't enough to completely preserve the part, but it helps.
+        p = self.policy
+        self.policy = p.clone(max_line_length=0)
+        try:
+            self._handle_multipart(msg)
+        finally:
+            self.policy = p
+
+    def _handle_message_delivery_status(self, msg):
+        # We can't just write the headers directly to self's file object
+        # because this will leave an extra newline between the last header
+        # block and the boundary.  Sigh.
+        blocks = []
+        for part in msg.get_payload():
+            s = self._new_buffer()
+            g = self.clone(s)
+            g.flatten(part, unixfrom=False, linesep=self._NL)
+            text = s.getvalue()
+            lines = text.split(self._encoded_NL)
+            # Strip off the unnecessary trailing empty line
+            if lines and lines[-1] == self._encoded_EMPTY:
+                blocks.append(self._encoded_NL.join(lines[:-1]))
+            else:
+                blocks.append(text)
+        # Now join all the blocks with an empty line.  This has the lovely
+        # effect of separating each block with an empty line, but not adding
+        # an extra one after the last one.
+        self._fp.write(self._encoded_NL.join(blocks))
+
+    def _handle_message(self, msg):
+        s = self._new_buffer()
+        g = self.clone(s)
+        # The payload of a message/rfc822 part should be a multipart sequence
+        # of length 1.  The zeroth element of the list should be the Message
+        # object for the subpart.  Extract that object, stringify it, and
+        # write it out.
+        # Except, it turns out, when it's a string instead, which happens when
+        # and only when HeaderParser is used on a message of mime type
+        # message/rfc822.  Such messages are generated by, for example,
+        # Groupwise when forwarding unadorned messages.  (Issue 7970.)  So
+        # in that case we just emit the string body.
+        payload = msg._payload
+        if isinstance(payload, list):
+            g.flatten(msg.get_payload(0), unixfrom=False, linesep=self._NL)
+            payload = s.getvalue()
+        else:
+            payload = self._encode(payload)
+        self._fp.write(payload)
+
+    # This used to be a module level function; we use a classmethod for this
+    # and _compile_re so we can continue to provide the module level function
+    # for backward compatibility by doing
+    #   _make_boudary = Generator._make_boundary
+    # at the end of the module.  It *is* internal, so we could drop that...
+    @classmethod
+    def _make_boundary(cls, text=None):
+        # Craft a random boundary.  If text is given, ensure that the chosen
+        # boundary doesn't appear in the text.
+        token = random.randrange(sys.maxsize)
+        boundary = ('=' * 15) + (_fmt % token) + '=='
+        if text is None:
+            return boundary
+        b = boundary
+        counter = 0
+        while True:
+            cre = cls._compile_re('^--' + re.escape(b) + '(--)?$', re.MULTILINE)
+            if not cre.search(text):
+                break
+            b = boundary + '.' + str(counter)
+            counter += 1
+        return b
+
+    @classmethod
+    def _compile_re(cls, s, flags):
+        return re.compile(s, flags)
+
+class BytesGenerator(Generator):
+    """Generates a bytes version of a Message object tree.
+
+    Functionally identical to the base Generator except that the output is
+    bytes and not string.  When surrogates were used in the input to encode
+    bytes, these are decoded back to bytes for output.  If the policy has
+    cte_type set to 7bit, then the message is transformed such that the
+    non-ASCII bytes are properly content transfer encoded, using the charset
+    unknown-8bit.
+
+    The outfp object must accept bytes in its write method.
+    """
+
+    # Bytes versions of this constant for use in manipulating data from
+    # the BytesIO buffer.
+    _encoded_EMPTY = b''
+
+    def write(self, s):
+        self._fp.write(str(s).encode('ascii', 'surrogateescape'))
+
+    def _new_buffer(self):
+        return BytesIO()
+
+    def _encode(self, s):
+        return s.encode('ascii')
+
+    def _write_headers(self, msg):
+        # This is almost the same as the string version, except for handling
+        # strings with 8bit bytes.
+        for h, v in msg.raw_items():
+            self._fp.write(self.policy.fold_binary(h, v))
+        # A blank line always separates headers from body
+        self.write(self._NL)
+
+    def _handle_text(self, msg):
+        # If the string has surrogates the original source was bytes, so
+        # just write it back out.
+        if msg._payload is None:
+            return
+        if _has_surrogates(msg._payload) and not self.policy.cte_type=='7bit':
+            if self._mangle_from_:
+                msg._payload = fcre.sub(">From ", msg._payload)
+            self._write_lines(msg._payload)
+        else:
+            super(BytesGenerator,self)._handle_text(msg)
+
+    # Default body handler
+    _writeBody = _handle_text
+
+    @classmethod
+    def _compile_re(cls, s, flags):
+        return re.compile(s.encode('ascii'), flags)
+
+
+_FMT = '[Non-text (%(type)s) part of message omitted, filename %(filename)s]'
+
+class DecodedGenerator(Generator):
+    """Generates a text representation of a message.
+
+    Like the Generator base class, except that non-text parts are substituted
+    with a format string representing the part.
+    """
+    def __init__(self, outfp, mangle_from_=True, maxheaderlen=78, fmt=None):
+        """Like Generator.__init__() except that an additional optional
+        argument is allowed.
+
+        Walks through all subparts of a message.  If the subpart is of main
+        type `text', then it prints the decoded payload of the subpart.
+
+        Otherwise, fmt is a format string that is used instead of the message
+        payload.  fmt is expanded with the following keywords (in
+        %(keyword)s format):
+
+        type       : Full MIME type of the non-text part
+        maintype   : Main MIME type of the non-text part
+        subtype    : Sub-MIME type of the non-text part
+        filename   : Filename of the non-text part
+        description: Description associated with the non-text part
+        encoding   : Content transfer encoding of the non-text part
+
+        The default value for fmt is None, meaning
+
+        [Non-text (%(type)s) part of message omitted, filename %(filename)s]
+        """
+        Generator.__init__(self, outfp, mangle_from_, maxheaderlen)
+        if fmt is None:
+            self._fmt = _FMT
+        else:
+            self._fmt = fmt
+
+    def _dispatch(self, msg):
+        for part in msg.walk():
+            maintype = part.get_content_maintype()
+            if maintype == 'text':
+                print(part.get_payload(decode=False), file=self)
+            elif maintype == 'multipart':
+                # Just skip this
+                pass
+            else:
+                print(self._fmt % {
+                    'type'       : part.get_content_type(),
+                    'maintype'   : part.get_content_maintype(),
+                    'subtype'    : part.get_content_subtype(),
+                    'filename'   : part.get_filename('[no filename]'),
+                    'description': part.get('Content-Description',
+                                            '[no description]'),
+                    'encoding'   : part.get('Content-Transfer-Encoding',
+                                            '[no encoding]'),
+                    }, file=self)
+
+
+# Helper used by Generator._make_boundary
+_width = len(repr(sys.maxsize-1))
+_fmt = '%%0%dd' % _width
+
+# Backward compatibility
+_make_boundary = Generator._make_boundary