bug#12705: 24.2.50; `Info-complete-menu-item' should use `add-to-list', not `push', to prevent duplicates

bug#12705: 24.2.50; `Info-complete-menu-item' should use `add-to-list', not `push', to prevent duplicates

[Drew Adams]

Subject line says it all.
 
This sexp:
(push (match-string-no-properties 1) completions)
 
should be changed to this:
(add-to-list 'completions (match-string-no-properties 1))

Otherwise the same entry can be added to `completions' multiple times.
 
This might not be manifested in *Completions*, because Emacs removes
duplicate candidates.  But in other completion setups (e.g. Icicles)
duplicate candidates (e.g. same display string, but perhaps different
alist elements) are sometimes allowed.
 
Yes, such other completion setups can specifically remove dups here.
But it would be more polite for `Info-complete-menu-item' to not create
dups in the first place.  There is never any reason for dups in this
context.

In GNU Emacs 24.2.50.1 (i386-mingw-nt5.1.2600)
 of 2012-10-15 on DANI-PC
Bzr revision: 110553 monnier@iro.umontreal.ca-20121015164957-6zms5w2js1xkldtg
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
 `configure --with-gcc (4.7) --no-opt --enable-checking --cflags
 -I../../libs/libxpm-3.5.8/include -I../../libs/libxpm-3.5.8/src
 -I../../libs/libpng-1.4.10 -I../../libs/zlib-1.2.6
 -I../../libs/giflib-4.1.4-1/include -I../../libs/jpeg-6b-4/include
 -I../../libs/tiff-3.8.2-1/include
 -I../../libs/libxml2-2.7.8-w32-bin/include/libxml2
 -I../../libs/gnutls-3.0.16/include
 -I../../libs/libiconv-1.14-2-mingw32-dev/include'
 

bug#12705: 24.2.50; `Info-complete-menu-item' should use `add-to-list', not `push', to prevent duplicates

[Chong Yidong]

"Drew Adams" <drew.adams@oracle.com> writes:

> This sexp:
> (push (match-string-no-properties 1) completions)
>  
> should be changed to this:
> (add-to-list 'completions (match-string-no-properties 1))
>
> Otherwise the same entry can be added to `completions' multiple times.
>  
> This might not be manifested in *Completions*, because Emacs removes
> duplicate candidates.  But in other completion setups (e.g. Icicles)
> duplicate candidates (e.g. same display string, but perhaps different
> alist elements) are sometimes allowed.

Sounds reasonable.  Done in trunk, using delete-dups instead of
add-to-list (in case info.el switches to lexical binding).

bug#12705: 24.2.50; `Info-complete-menu-item' should use `add-to-list', not `push', to prevent duplicates

[Drew Adams]

> Sounds reasonable.  Done in trunk, using delete-dups instead of
> add-to-list (in case info.el switches to lexical binding).

Thx.

Just curious - how would add-to-list interfere with lexical binding (or vice
versa)?

Seems odd that we would add and then delete, instead of adding only if not
present, just to dance around (the possibility of) lexical binding.

To be clear, I have no objection at all - nothing wrong with adding and then
deleting.  I'd just like to understand the problem being avoided.

bug#12705: 24.2.50; `Info-complete-menu-item' should use `add-to-list', not `push', to prevent duplicates

[Stefan Monnier]

>> Sounds reasonable.  Done in trunk, using delete-dups instead of
>> add-to-list (in case info.el switches to lexical binding).

Isn't it better to use cl-pushnew?


        Stefan