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#11731: simplify/enhance parser/generator API by introducing policy objects.

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This new interface will also allow for future planned enhancements
in control over the parser/generator without requiring any additional
complexity in the parser/generator API.

Patch reviewed by Éric Araujo and Barry Warsaw.
This commit is contained in:
R David Murray 2011-04-18 13:59:37 -04:00
parent ce16be91dc
commit 3edd22ac95
13 changed files with 912 additions and 81 deletions
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62
Lib/email/generator.py
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@ -13,8 +13,10 @@ import random
import warnings
from io import StringIO, BytesIO
from email import policy
from email.header import Header
from email.message import _has_surrogates
import email.charset as _charset
UNDERSCORE = '_'
NL = '\n' # XXX: no longer used by the code below.
@ -33,7 +35,8 @@ class Generator:
# Public interface
#
def __init__(self, outfp, mangle_from_=True, maxheaderlen=78):
def __init__(self, outfp, mangle_from_=True, maxheaderlen=None, *,
policy=policy.default):
"""Create the generator for message flattening.
outfp is the output file-like object for writing the message to. It
@ -49,16 +52,23 @@ class Generator:
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._maxheaderlen = (maxheaderlen if maxheaderlen is not None else
policy.max_line_length)
self.policy = policy
def write(self, s):
# Just delegate to the file object
self._fp.write(s)
def flatten(self, msg, unixfrom=False, linesep='\n'):
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.
@ -70,17 +80,15 @@ class Generator:
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 the most useful for typical
Python applications, but it can be set to \r\n to produce RFC-compliant
line separators when needed.
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.
self._NL = linesep
self._encoded_NL = self._encode(linesep)
self._NL = linesep if linesep is not None else self.policy.linesep
self._encoded_NL = self._encode(self._NL)
self._EMPTY = ''
self._encoded_EMTPY = self._encode('')
if unixfrom:
@ -338,7 +346,10 @@ class BytesGenerator(Generator):
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.
bytes, these are decoded back to bytes for output. If the policy has
must_be_7bit set true, 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.
"""
@ -361,21 +372,22 @@ class BytesGenerator(Generator):
# strings with 8bit bytes.
for h, v in msg._headers:
self.write('%s: ' % h)
if isinstance(v, Header):
self.write(v.encode(maxlinelen=self._maxheaderlen)+NL)
elif _has_surrogates(v):
# If we have raw 8bit data in a byte string, we have no idea
# what the encoding is. There is no safe way to split this
# string. If it's ascii-subset, then we could do a normal
# ascii split, but if it's multibyte then we could break the
# string. There's no way to know so the least harm seems to
# be to not split the string and risk it being too long.
self.write(v+NL)
else:
# Header's got lots of smarts and this string is safe...
header = Header(v, maxlinelen=self._maxheaderlen,
header_name=h)
self.write(header.encode(linesep=self._NL)+self._NL)
if isinstance(v, str):
if _has_surrogates(v):
if not self.policy.must_be_7bit:
# If we have raw 8bit data in a byte string, we have no idea
# what the encoding is. There is no safe way to split this
# string. If it's ascii-subset, then we could do a normal
# ascii split, but if it's multibyte then we could break the
# string. There's no way to know so the least harm seems to
# be to not split the string and risk it being too long.
self.write(v+NL)
continue
h = Header(v, charset=_charset.UNKNOWN8BIT, header_name=h)
else:
h = Header(v, header_name=h)
self.write(h.encode(linesep=self._NL,
maxlinelen=self._maxheaderlen)+self._NL)
# A blank line always separates headers from body
self.write(self._NL)
@ -384,7 +396,7 @@ class BytesGenerator(Generator):
# just write it back out.
if msg._payload is None:
return
if _has_surrogates(msg._payload):
if _has_surrogates(msg._payload) and not self.policy.must_be_7bit:
self.write(msg._payload)
else:
super(BytesGenerator,self)._handle_text(msg)