GNU bug report logs - #53012
28.0.90; completion--nth-completion: Throw a meaningful error

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Daniel Mendler <mail <at> daniel-mendler.de>
To: bug-gnu-emacs <at> gnu.org
Cc: Stefan Monnier <monnier <at> iro.umontreal.ca>
Subject: 28.0.90; completion--nth-completion: Throw a meaningful error
Date: Tue, 4 Jan 2022 21:12:47 +0100

In the context of the GNU ELPA Vertico/Mct/Orderless/Embark ecosystem we
teach users to adjust the completion style. Unfortunately
completion--nth-completion is not very robust against misconfiguration.
I propose to throw a more meaningful error instead of the nil error.
Patch follows.

---

From da92169572e375facabb28b6d3c14cb2158ab1c9 Mon Sep 17 00:00:00 2001
From: Daniel Mendler <mail <at> daniel-mendler.de>
Date: Tue, 4 Jan 2022 21:08:04 +0100
Subject: [PATCH] completion--nth-completion: Throw meaningful error

If a configured completion style does not exist, throw a meaningful
error. Also make completion-styles-alist a defvar, since completion
styles like orderless extend it.
---
 lisp/minibuffer.el | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
index 1d596694e4..ab760a42d1 100644
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -900,7 +900,7 @@ completion-auto-help
 the second failed attempt to complete."
   :type '(choice (const nil) (const t) (const lazy)))

-(defconst completion-styles-alist
+(defvar completion-styles-alist
   '((emacs21
      completion-emacs21-try-completion completion-emacs21-all-completions
      "Simple prefix-based completion.
@@ -1076,9 +1076,10 @@ completion--nth-completion
          (result-and-style
           (completion--some
            (lambda (style)
-             (let ((probe (funcall (nth n (assq style
-                                                completion-styles-alist))
-                                   string table pred point)))
+             (let ((probe (funcall
+                           (or (nth n (assq style completion-styles-alist))
+                               (error "Invalid completion style %s" style))
+                           string table pred point)))
                (and probe (cons probe style))))
            (completion--styles md)))
          (adjust-fn (get (cdr result-and-style)
'completion--adjust-metadata)))
-- 
2.20.1

Message #8 received at 53012 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Daniel Mendler <mail <at> daniel-mendler.de>
Cc: 53012 <at> debbugs.gnu.org
Subject: Re: 28.0.90; completion--nth-completion: Throw a meaningful error
Date: Tue, 04 Jan 2022 19:19:22 -0500

Daniel Mendler [2022-01-04 21:12:47] wrote:
> In the context of the GNU ELPA Vertico/Mct/Orderless/Embark ecosystem we
> teach users to adjust the completion style. Unfortunately
> completion--nth-completion is not very robust against misconfiguration.
> I propose to throw a more meaningful error instead of the nil error.

Thanks, looks good.
Pushed to `master`.


        Stefan

Message #11 received at 53012 <at> debbugs.gnu.org (full text, mbox):

From: Daniel Mendler <mail <at> daniel-mendler.de>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 53012 <at> debbugs.gnu.org
Subject: Re: 28.0.90; completion--nth-completion: Throw a meaningful error
Date: Wed, 5 Jan 2022 01:42:19 +0100

On 1/5/22 1:19 AM, Stefan Monnier wrote:
> Daniel Mendler [2022-01-04 21:12:47] wrote:
>> In the context of the GNU ELPA Vertico/Mct/Orderless/Embark ecosystem we
>> teach users to adjust the completion style. Unfortunately
>> completion--nth-completion is not very robust against misconfiguration.
>> I propose to throw a more meaningful error instead of the nil error.
> 
> Thanks, looks good.
> Pushed to `master`.

Thanks!

Message #16 received at 53012-done <at> debbugs.gnu.org (full text, mbox):

From: Stefan Kangas <stefan <at> marxist.se>
To: Daniel Mendler <mail <at> daniel-mendler.de>
Cc: 53012-done <at> debbugs.gnu.org, Stefan Monnier <monnier <at> iro.umontreal.ca>
Subject: Re: bug#53012: 28.0.90; completion--nth-completion: Throw a
 meaningful error
Date: Sun, 9 Jan 2022 09:31:36 -0600

Daniel Mendler <mail <at> daniel-mendler.de> writes:

> On 1/5/22 1:19 AM, Stefan Monnier wrote:
>> Daniel Mendler [2022-01-04 21:12:47] wrote:
>>> In the context of the GNU ELPA Vertico/Mct/Orderless/Embark ecosystem we
>>> teach users to adjust the completion style. Unfortunately
>>> completion--nth-completion is not very robust against misconfiguration.
>>> I propose to throw a more meaningful error instead of the nil error.
>>
>> Thanks, looks good.
>> Pushed to `master`.
>
> Thanks!

I'm therefore closing this bug report.

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