Mailcap Fix
Note: An official fix for this issue was released in Python 3.6.0. This package now acts as a backport for all older versions of python.
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-fixExample
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
| 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 |