[Python-Dev] argparse ambiguity handling

[Cameron Simpson]

On 20Apr2010 15:27, Neal Becker <ndbecker2 at gmail.com> wrote:
| Steven Bethard wrote:
| 
| > On Tue, Apr 20, 2010 at 11:55 AM, Neal Becker <ndbecker2 at gmail.com> wrote:
| >> I've noticed argparse ambiguity handling has changed a bit over last few
| >> revisions.
| >>
| >> I have cases where 1 valid input is a prefix of another:
| >>
| >> e.g.:
| >> '--string'
| >> '--string2'
| >>
| >> With the most recent 1.1, the behavior is:
| >>
| >> --string=hello
| >>
| >> is accepted, while:
| >>
| >> --strin=hello
| >>
| >> is marked as ambiguous.
| >>
| >> I'm OK with this, but just want to know if there is agreement that this
| >> is the behavior we want.
| > 
| > I don't have a strong feeling about this. What was the behavior before?
| > Steve
| 
| At least 1 earlier version said that even exact match was ambiguous.
| 
| I have a preference to allow at least exact matches to succeed even in the 
| case of ambiguity - mainly because I accidentally created this already once, 
| and I feel it's better to at least work somewhat.  Not sure if there is any 
| more elegant solution.  OTOH, I feel this is somewhat inelegant, as it 
| appears to treat exact match as a special case.

I think the new behaviour is desirable. Plenty of commands have both
--foo and --foo-tweak. Usually because --foo came first and --foo-tweak
came later, or simply because --foo is the simple and obvious and
commonly wanted mode and --foo-tweak is a special case.

Real world example: rsync and the --delete* options. I'm sure plenty of
others can be found.

The new behaviour makes this doable. The old behaviour made it
unimplementable. Maybe it is desirable to be _able_ to forbid this
arguably-ambiguous option set, but I definitely feel that the current
behaviour should be available.

Cheers,
-- 
Cameron Simpson <cs at zip.com.au> DoD#743
http://www.cskk.ezoshosting.com/cs/

If it wasn't for lawyers, we wouldn't need them.