Re: master 67ab357cdcc 7/7: Support treesit-thing-settings in search functions

[Yuan Fu]

> On Apr 15, 2023, at 2:58 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> Date: Sat, 15 Apr 2023 09:58:09 +0300
>> From: Eli Zaretskii <eliz@gnu.org>
>> Cc: emacs-devel@gnu.org, casouri@gmail.com
>> 
>>> From: Po Lu <luangruo@yahoo.com>
>>> Cc: Yuan Fu <casouri@gmail.com>
>>> Date: Sat, 15 Apr 2023 10:43:21 +0800
>>> 
>>> Yuan Fu <casouri@gmail.com> writes:
>>> 
>>>> +/* Assq but doesn't signal.  */
>>>> +static Lisp_Object
>>>> +safe_assq (Lisp_Object key, Lisp_Object alist)
>>>> +{
>>>> +  Lisp_Object tail = alist;
>>>> +  FOR_EACH_TAIL_SAFE (tail)
>>>> +    if (CONSP (XCAR (tail)) && EQ (XCAR (XCAR (tail)), key))
>>>> +      return XCAR (tail);
>>>> +  return Qnil;
>>>> +}
>>> 
>>> Please, write more descriptive doc strings.  I would write:
>>> 
>>>  /* Like `assq_no_quit', except it avoids chasing after circular
>>>     lists.  */
>> 
>> It is more efficient to just go ahead and make minor changes like
>> that, than start discussions about them.

And rest assured that I do read git logs and I’ll take note of changes you 
made. Eli and many others have fixes mistakes I made in the code, I’m very 
grateful and try my best to learn from it.

> 
> Btw, Yuan: any reason you couldn't use the existing assq_no_quit here?

To be very honest I didn’t know its existence before. But safe_assq is indeed 
necessary, because assq_no_quit assumes the list is not circular and doesn’t 
try to detect one.

For this particular use-case I just don’t want assq to signal any error, but I 
do want it to detect errors. Circular error, malformed alist, or simply 
couldn’t find the key, all of these will be reported to the user as “couldn’t 
find the key” (as an error). This is easier to understand for the user and 
easier for me to implement (than using unwind-protect and let assq signal).

Yuan