Re: Simplification of `affixation-function`

[Daniel Mendler <mail@daniel-mendler.de>]

On 4/24/21 10:22 PM, Juri Linkov wrote:
> If the logic of specifying the elements is too confusing,
> then such simplification is welcome.

> Please note that only the documentation could be changed
> to remove mentions of the ability to specify only suffix
> for `affixation-function`.  But code will remain unchanged
> because internally it depends on the predefined order of elements:
> “completion + suffix” or “completion + prefix + suffix”.
> There is no backward-compatible way to change this order.

I think it is slightly confusing and unnecessarily complicated. But if 
you want to retain backward compatibility, there is no way back. However 
since the `affixation-function` has only been introduced recently, there 
should still be a time window to change the definition? There is no 
released version of Emacs with `affixation-function` support.

(If it is decided to change the definition it should be feasible to go 
over all ELPA/MELPA and apply patches to all packages which already make 
use of the `affixation-function`.)

> More than three elements are already supported since e.g. the
> total length is calculated as a sum of lengths of all strings:
> 
>    (apply #'+ (mapcar #'string-width str))

I see. So all the later elements are suffixes and concatenated? This 
seems like an unnecessary completion given that the completion-table 
implementor can already concatenate all the suffixes. Or is the idea 
that the UI can show all these suffixes in some kind of table-like view?
It seems that there is at least need for better documentation.

My proposal is to only allow three-element lists and remove support to 
specify only the suffix.

And one could keep the door open by allowing more than three element 
lists for additional annotations. Let's say you want to specify some 
additional help/tool-tip text for example.

Daniel