* Check intersection of two sets explicitly
Comparing ``len(a) > ``len(a - b)`` is essentially looking for an
intersection between the two sets. If set ``b`` does not intersect ``a``
then ``len(a - b)`` will be equal to ``len(a)``. This logic is more
clearly expressed as ``a & b``.
* Change while/pop to a for-loop
Copying the list, then repeatedly popping the first element was
unnecessarily slow. I also cleaned up a couple other inefficiencies.
There's no need to unpack a tuple, then re-pack and append it. The list
can be created with the first element instead of empty. Secondly, the
``endswith`` method returns a bool, so there's no need for an if-
statement to set ``encoding`` to True or False.
* Use set.intersection to check for intersections
``a.intersection(b)`` method is more clear of purpose than ``not
a.isdisjoint(b)`` and avoids an unnecessary set construction that ``a &
set(b)`` performs.
* Use not isdisjoint instead of intersection
While it reads slightly worse, the isdisjoint method will stop when it
finds a counterexample and returns a bool, rather than looping over the
entire iterable and constructing a new set.
* bpo-35805: Add parser for Message-ID header.
This parser is based on the definition of Identification Fields from RFC 5322
Sec 3.6.4.
This should also prevent folding of Message-ID header using RFC 2047 encoded
words and hence fix bpo-35805.
* Prevent folding of non-ascii message-id headers.
* Add fold method to MsgID token to prevent folding.
The original algorithm tried to delegate the folding to the tokens so
that those tokens whose folding rules differed could specify the
differences. However, this resulted in a lot of duplicated code because
most of the rules were the same.
The new algorithm moves all folding logic into a set of functions
external to the token classes, but puts the information about which
tokens can be folded in which ways on the tokens...with the exception of
mime-parameters, which are a special case (which was not even
implemented in the old folder).
This algorithm can still probably be improved and hopefully simplified
somewhat.
Note that some of the test expectations are changed. I believe the
changes are toward more desirable and consistent behavior: in general
when (re) folding a line the canonical version of the tokens is
generated, rather than preserving errors or extra whitespace.
It is unlikely anyone is using the fact that the dictionary returned
by the 'params' attribute was previously writable, but even if someone
is the API is provisional so this kind of change is acceptable (and
needed, to get the API "right" before it becomes official).
Patch by Stéphane Wirtel.
This code passes all the same tests that the existing RFC mime header
parser passes, plus a bunch of additional ones.
There are a couple of commented out tests where there are issues with the
folding. The folding doesn't normally get invoked for headers parsed from
source, and the cases are marginal anyway (headers with invalid binary data)
so I'm not worried about them, but will fix them after the beta.
There are things that can be done to make this API even more convenient, but I
think this is a solid foundation worth having. And the parser is a full RFC
parser, so it handles cases that the current parser doesn't. (There are also
probably cases where it fails when the current parser doesn't, but I haven't
found them yet ;)
Oh, yeah, and there are some really ugly bits in the parser for handling some
'postel' cases that are unfortunately common.
I hope/plan to to eventually refactor a lot of the code in the parser which
should reduce the line count...but there is no escaping the fact that the
error recovery is welter of special cases.
When I made the checkin of the provisional email policy, I knew that
Address and Group needed to be made accessible from somewhere. The more
I looked at it, though, the more it became clear that since this is a
provisional API anyway, there's no good reason to hide headerregistry as
a private API. It was designed to ultimately be part of the public API,
and so it should be part of the provisional API.
This patch fully documents the headerregistry API, and deletes the
abbreviated version of those docs I had added to the provisional policy
docs.
