mailcap-fix 1.0.1

A patched mailcap module that conforms to RFC 1524

Note

A fix has now been merged into Python 3.6.0.

This package remains as a backport for previous versions.

Summary

This package patches the python standard library’s mailcap module in order to correctly handle windcard entries.

The bug is documented on the bug tracker here: issue 14977

Installation

$ pip install mailcap-fix

Example

Consider a mailcap file that contains the following two lines

image/*; feh %s
image/jpeg; eog %s

Because the image/* entry is defined first, it should take precedence over the image/jpeg entry when searching for a match. This behavior is defined by RFC 1524. However, the standard library’s implementation will always evaluate wildcard entries last.

Before

>>> import mailcap
>>> d = mailcap.getcaps()
>>> # Incorrectly returns the second entry
>>> mailcap.findmatch(d, 'image/jpeg', filename='test.jpg')
('eog test.jpg', {'view': 'eog %s'})

After

>>> from mailcap_fix import mailcap
>>> d = mailcap.getcaps()
>>> # Correctly returns the wildcard entry
>>> mailcap.findmatch(d, 'image/jpeg', filename='test.jpg')
('feh test.jpg', {'view': 'feh %s', 'lineno': 0})

How it works

The goal of this patch is to conform to RFCC 1524, while preserving as much backwards compatibility as possible and without adding any “magic”.

mailcap_fix adds a new field lineno to each entry in the mailcap dict. This line number is then used to sort entries in descending order when searching for a match. For backwards compatability, if lineno is not present entries will simply not be sorted. Because RFC 1524 defines a whitelist of valid mailcap fieldnames, the addition of lineno should not conflict with any other mailcap fields.

Benchmark

Python 3.4.0

Ubuntu 14.04 LTS 64bit

Intel® Core™ i5-3210M CPU @ 2.50GHz × 4

8 GiB RAM

mailcap.get_caps() - per file
	mailcap	mailcap_fix
mailcap_short.txt	0.081881 ms	0.084525 ms
mailcap_long.txt	17.746289 ms	18.407623 ms

mailcap.lookup() - avg function call
	mailcap	mailcap_fix
mailcap_short.txt	0.000996 ms	0.003144 ms
mailcap_long.txt	0.000798 ms	0.002731 ms