Re: User-defined completion listing

[Peter Stephenson <pws@ifh.de>]

"Bart Schaefer" wrote:
> }   compctl ... -Y '$array'
> } or
> }   compctl ... -Y 'func'
> 
> I must confess confusion as to why you'd do it this way.
> 
> If you're going to examine the first character and behave differently
> when it is '$', you could do that with -X and not need a new option.

-X doesn't do the right thing.  It gets displayed with completions,
if there's no unique match, not just listings.  Further, it gets displayed
in addition to a listing, just above.  We want something to be displayed
instead of a listing.  If you simply use -X, there's no way of adapting
the listing at all, and it would be wrong to misuse -X for that
purpose.  Also, -Y *has* to be generated separately for each
completion, because it depends on the actual list; -X doesn't, so
there's no real rationale for making it support $var.

> If you're going to expand a variable, why does it have to be an array?
> The parameter to -X is just a string.

Because -Y replaces a list; it's natural to generate the replacement
list as an array.  As with literal arrays (quoted below), I'd quite
like to alter get_user_var() to turn a scalar into a single element
array, which will solve this problem quite neatly, it just wasn't
a necessary part of yesterday's patch.  I certainly agree it's
desirable.

> If you're going to substitute a string, why pass it around with $reply?

I don't understand this.  The $reply comes only from the function.
The exact $reply array is used for the listing.  There is no more
substitution and $reply has always been for communication back from
functions. Do you mean `why not use $REPLY'?  The answer is because
you can't replace a complete listing with that.  It seems silly
to use both.

In more abstract terms, what gets displayed in a completion listing
is always an array of possibilities.  The whole point of the -Y option
is to allow you to alter that.  It is entirely natural that this altered
list would be an array.  It just so happens you can get away with a one
element array with everything stuck together, if you want.

> } Another thing under the `could perhaps be better, but it's time I did
> } some work' heading:  literal arrays are allowed as with -k, i.e. -Y
> } '(option1 option2 ...)', but there's no way of getting a literal
> } string there.
> 
> Why do you need to pass a literal string to -Y when you can use -X ?

You can't, not for the same thing.  See above.  -X and -Y are
entirely different:  -X gives a single, fixed banner heading for
the listing and for the completion; -Y gives a list of completions
to replace the ones shown when displaying completions.

-- 
Peter Stephenson <pws@ifh.de>       Tel: +49 33762 77366
WWW:  http://www.ifh.de/~pws/       Fax: +49 33762 77413
Deutsches Elektronen-Synchrotron --- Institut fuer Hochenergiephysik Zeuthen
DESY-IfH, Platanenallee 6, 15738 Zeuthen, Germany.