194 lines
8.6 KiB
Python
194 lines
8.6 KiB
Python
"""This will be the home for the policy that hooks in the new
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code that adds all the email6 features.
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"""
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from __future__ import unicode_literals
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from __future__ import division
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from __future__ import absolute_import
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from future.builtins import super
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from future.standard_library.email._policybase import (Policy, Compat32,
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compat32, _extend_docstrings)
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from future.standard_library.email.utils import _has_surrogates
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from future.standard_library.email.headerregistry import HeaderRegistry as HeaderRegistry
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__all__ = [
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'Compat32',
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'compat32',
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'Policy',
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'EmailPolicy',
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'default',
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'strict',
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'SMTP',
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'HTTP',
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]
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@_extend_docstrings
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class EmailPolicy(Policy):
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"""+
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PROVISIONAL
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The API extensions enabled by this policy are currently provisional.
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Refer to the documentation for details.
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This policy adds new header parsing and folding algorithms. Instead of
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simple strings, headers are custom objects with custom attributes
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depending on the type of the field. The folding algorithm fully
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implements RFCs 2047 and 5322.
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In addition to the settable attributes listed above that apply to
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all Policies, this policy adds the following additional attributes:
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refold_source -- if the value for a header in the Message object
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came from the parsing of some source, this attribute
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indicates whether or not a generator should refold
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that value when transforming the message back into
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stream form. The possible values are:
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none -- all source values use original folding
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long -- source values that have any line that is
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longer than max_line_length will be
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refolded
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all -- all values are refolded.
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The default is 'long'.
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header_factory -- a callable that takes two arguments, 'name' and
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'value', where 'name' is a header field name and
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'value' is an unfolded header field value, and
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returns a string-like object that represents that
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header. A default header_factory is provided that
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understands some of the RFC5322 header field types.
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(Currently address fields and date fields have
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special treatment, while all other fields are
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treated as unstructured. This list will be
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completed before the extension is marked stable.)
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"""
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refold_source = 'long'
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header_factory = HeaderRegistry()
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def __init__(self, **kw):
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# Ensure that each new instance gets a unique header factory
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# (as opposed to clones, which share the factory).
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if 'header_factory' not in kw:
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object.__setattr__(self, 'header_factory', HeaderRegistry())
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super().__init__(**kw)
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def header_max_count(self, name):
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"""+
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The implementation for this class returns the max_count attribute from
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the specialized header class that would be used to construct a header
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of type 'name'.
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"""
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return self.header_factory[name].max_count
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# The logic of the next three methods is chosen such that it is possible to
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# switch a Message object between a Compat32 policy and a policy derived
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# from this class and have the results stay consistent. This allows a
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# Message object constructed with this policy to be passed to a library
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# that only handles Compat32 objects, or to receive such an object and
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# convert it to use the newer style by just changing its policy. It is
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# also chosen because it postpones the relatively expensive full rfc5322
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# parse until as late as possible when parsing from source, since in many
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# applications only a few headers will actually be inspected.
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def header_source_parse(self, sourcelines):
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"""+
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The name is parsed as everything up to the ':' and returned unmodified.
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The value is determined by stripping leading whitespace off the
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remainder of the first line, joining all subsequent lines together, and
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stripping any trailing carriage return or linefeed characters. (This
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is the same as Compat32).
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"""
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name, value = sourcelines[0].split(':', 1)
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value = value.lstrip(' \t') + ''.join(sourcelines[1:])
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return (name, value.rstrip('\r\n'))
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def header_store_parse(self, name, value):
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"""+
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The name is returned unchanged. If the input value has a 'name'
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attribute and it matches the name ignoring case, the value is returned
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unchanged. Otherwise the name and value are passed to header_factory
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method, and the resulting custom header object is returned as the
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value. In this case a ValueError is raised if the input value contains
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CR or LF characters.
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"""
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if hasattr(value, 'name') and value.name.lower() == name.lower():
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return (name, value)
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if isinstance(value, str) and len(value.splitlines())>1:
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raise ValueError("Header values may not contain linefeed "
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"or carriage return characters")
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return (name, self.header_factory(name, value))
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def header_fetch_parse(self, name, value):
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"""+
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If the value has a 'name' attribute, it is returned to unmodified.
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Otherwise the name and the value with any linesep characters removed
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are passed to the header_factory method, and the resulting custom
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header object is returned. Any surrogateescaped bytes get turned
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into the unicode unknown-character glyph.
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"""
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if hasattr(value, 'name'):
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return value
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return self.header_factory(name, ''.join(value.splitlines()))
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def fold(self, name, value):
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"""+
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Header folding is controlled by the refold_source policy setting. A
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value is considered to be a 'source value' if and only if it does not
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have a 'name' attribute (having a 'name' attribute means it is a header
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object of some sort). If a source value needs to be refolded according
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to the policy, it is converted into a custom header object by passing
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the name and the value with any linesep characters removed to the
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header_factory method. Folding of a custom header object is done by
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calling its fold method with the current policy.
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Source values are split into lines using splitlines. If the value is
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not to be refolded, the lines are rejoined using the linesep from the
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policy and returned. The exception is lines containing non-ascii
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binary data. In that case the value is refolded regardless of the
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refold_source setting, which causes the binary data to be CTE encoded
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using the unknown-8bit charset.
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"""
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return self._fold(name, value, refold_binary=True)
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def fold_binary(self, name, value):
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"""+
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The same as fold if cte_type is 7bit, except that the returned value is
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bytes.
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If cte_type is 8bit, non-ASCII binary data is converted back into
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bytes. Headers with binary data are not refolded, regardless of the
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refold_header setting, since there is no way to know whether the binary
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data consists of single byte characters or multibyte characters.
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"""
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folded = self._fold(name, value, refold_binary=self.cte_type=='7bit')
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return folded.encode('ascii', 'surrogateescape')
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def _fold(self, name, value, refold_binary=False):
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if hasattr(value, 'name'):
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return value.fold(policy=self)
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maxlen = self.max_line_length if self.max_line_length else float('inf')
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lines = value.splitlines()
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refold = (self.refold_source == 'all' or
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self.refold_source == 'long' and
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(lines and len(lines[0])+len(name)+2 > maxlen or
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any(len(x) > maxlen for x in lines[1:])))
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if refold or refold_binary and _has_surrogates(value):
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return self.header_factory(name, ''.join(lines)).fold(policy=self)
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return name + ': ' + self.linesep.join(lines) + self.linesep
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default = EmailPolicy()
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# Make the default policy use the class default header_factory
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del default.header_factory
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strict = default.clone(raise_on_defect=True)
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SMTP = default.clone(linesep='\r\n')
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HTTP = default.clone(linesep='\r\n', max_line_length=None)
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