[Mailman-Developers] Regexp filtering

[Stephen J. Turnbull]

On Mailman-Users, Mark Sapiro writes:

 > Further, in the ban_list (and many other places in Mailman) if an
 > address is intended to be a regular expression pattern, it must begin
 > with '^', so you really want
 > 
 > ^.*@domain\.com$
 > 
 > to match any_address at domain.com.

I hope we haven't propagated this rather user-unfriendly interface
(the convention of accepting both regexps and literals, distinguishing
by "^" in column 0) to Mailman 3.  Even as a Python programmer, I find
Mark's post somewhat confusing: I would design filters using
re.search, so that the above would actually be equivalent as a Python
regular expression to r"@domain\.com$".  OTOH, if the implementation
uses re.match, the "^" is redundant, so I have a "say what?!" event.

If we have, I propose changing it to

    Ban these addresses, one entry per line: [                ]
    [ ] Entries are regular expressions.

or something like that.  We also ought to have a "Python features for
Mailman administrators" section of the FAQ, starting with "what is a
regular expression", and giving examples of how to accomplish common
tasks like banning a whole domain with regular expressions.  Typical
regexp FAQs are hard for non-programmers (and even beginning
programmers) to grasp.

I don't have time to actually work on these now, but if there's uptake
on the suggestion ("let's think about it" at +0 or above :-) I'll file
issues.