Completion with different values and displayed things

Completion with different values and displayed things

[mbork]

Hi all!

I have a list of "things" and I need to use `completing-read' (or
another completion mechanism) to enable the user to select one of them.
Here's the problem.  Every "thing" has, say, three things, like
(:name "Thing" :description "The important thing" :id 1337)
I want my completion to:
- complete on :name
- display also :description (there could be two different "things" with
  the same :name's but different :description's)
- and return :id

I use Ivy, but I'd prefer to make this work with any completion
framework (or even with Emacs vanilla completion).

Does Emacs has anything like this?  More or less, I'd like an equivalent
of HTML's <select> where displayed thing is different than the "value"
attribute.  It is important though to use some sort of completion
instead of e.g. displaying all options annotated by numbers/letters and
letting the user type the number or a letter associated with the one
they want - there are too many of them for this to be comfortable.

TIA,

-- 
Marcin Borkowski
https://mbork.pl
https://crimsonelevendelightpetrichor.net/

Re: Completion with different values and displayed things

[Stefan Monnier via Users list for the GNU Emacs text editor]

> I want my completion to:
> - complete on :name
> - display also :description (there could be two different "things" with
>   the same :name's but different :description's)

The completion mechanism "funnels" everything through the string the
users type (either directly or via completion), so if completion in only
based on `:name`s (i.e. the strings the user can enter will only ever
take the form of one of the `:name`s), then there is no way for the users
to specify which of several entries they meant if those entries share
the same `:name`.

IOW, make sure the thing on which they complete is unique.

Also, the completion API doesn't conveniently let you display just the
`:description`: you can use the `annotation` metadata (see
`completion-metadata`) to *add* the `:description` to the thing on which
the users complete (e.g. the `:name`), but not to replace it.

As for returning the `:id`, just do it manually after the call to
`completing-read` by searching for the matching entry and extracting its
`:id`.


        Stefan