bug#39143: 26.3; `widget-complete' in `customize-option'

bug#39143: 26.3; `widget-complete' in `customize-option'

[Drew Adams]

emacs -Q

`M-x customize-option default-frame-alist'

Click `INS'.

Enter `cursor-color' for field `Parameter: '.

Put cursor at beginning of field `Value: ', and delete the default
value, `nil'.

Use `M-TAB' (or `ESC TAB').

You get this error/message: "Not in an editable field".

Two parts to this report.  The first is a bug; the second is an
enhancement request for handling of option `default-frame-alist' and
other frame-alist options.

1. That message is incorrect.  The cursor is definitely in an editable
field.  (Same incorrect message if you first type `Blu', then `M-TAB'.)

2. Emacs should provide reasonable completion for both fields,
`Parameter' and `Value', for `default-frame-alist'.

2a. Completion can be lax for `Parameter', providing candidates that are
predefined parameters, but letting you enter other values too.

2b. Completion can perhaps be strict for `Value' for some known
parameters, but it would probably be better if it were lax in all cases,
unless there is a strict requirement about the possible values in some
case.


In GNU Emacs 26.3 (build 1, x86_64-w64-mingw32)
 of 2019-08-29 built on CIRROCUMULUS
Repository revision: 96dd0196c28bc36779584e47fffcca433c9309cd
Windowing system distributor 'Microsoft Corp.', version 10.0.17763

bug#39143: 26.3; `widget-complete' in `customize-option'

[Eli Zaretskii]

> Date: Wed, 15 Jan 2020 09:54:58 -0800 (PST)
> From: Drew Adams <drew.adams@oracle.com>
> 
> emacs -Q
> 
> `M-x customize-option default-frame-alist'
> 
> Click `INS'.
> 
> Enter `cursor-color' for field `Parameter: '.
> 
> Put cursor at beginning of field `Value: ', and delete the default
> value, `nil'.
> 
> Use `M-TAB' (or `ESC TAB').
> 
> You get this error/message: "Not in an editable field".

In Emacs 27 get the message "No completions available for this field"
instead.  So this problem is already solved.

> 1. That message is incorrect.  The cursor is definitely in an editable
> field.  (Same incorrect message if you first type `Blu', then `M-TAB'.)

This part is already solved.

> 2. Emacs should provide reasonable completion for both fields,
> `Parameter' and `Value', for `default-frame-alist'.

It does provide completions for Parameter, although it's debatable
whether they are "reasonable".

bug#39143: 26.3; `widget-complete' in `customize-option'

[Drew Adams]

> > You get this error/message: "Not in an editable field".
> > 1. That message is incorrect.  The cursor is definitely in an
> > editable field.
> 
> In Emacs 27 get the message "No completions available for this field"
> instead.  So this problem is already solved.

Good.  Thanks for the quick reply.

> > 2. Emacs should provide reasonable completion for both fields,
> > `Parameter' and `Value', for `default-frame-alist'.
> 
> It does provide completions for Parameter, although it's debatable
> whether they are "reasonable".

I guess you mean in Emacs 27.  (Not in Emacs 26, AFAICT.)

Trying an Emacs 27 snapshot from 2019-12-28, it seems
that the completion is reasonable enough.

So this report can be classified as an enhancement request
that we provide some (lax) completion for `Value'.  Thx.