Re: Adding 'compat' from ELPA as an optional dependency to ERC

[Philip Kaludercic <philipk@posteo.net>]

"J.P." <jp@neverwas.me> writes:

> Philip Kaludercic <philipk@posteo.net> writes:
>
>> "J.P." <jp@neverwas.me> writes:
>>
>>>                              Although, I believe doing so would also
>>> define compat- prefixed variants in all versions of Emacs, the idea
>>> being to save third-party packages from having to do stuff like
>>>
>>>   (defmacro erc-compat--json-parse-string (string &rest args)
>>>     `(,(if (fboundp 'compat-json-parse-string)
>>>            'compat-json-parse-string
>>>          'json-parse-string)
>>>       ,string
>>>       ,@args))
>>
>> If a function like this were to be definied upstream
>>
>>         (defun get-compatibility-func (name)
>>           "Return the function NAME of a compatibility alias."
>>           (let* ((compat (intern-soft (format "compat-%s" name))))
>>             (or (symbol-function (if (fboundp name) name compat))
>>                 (error "No definition for %S could be found" name))))
>>
>> then all that ERC would have to do is
>>
>>         (defalias 'erc-json-parse-string
>>           (get-compatibility-func 'json-parse-string))
>>
>
> Nice. That looks really handy.
>
> (BTW, wouldn't a real life `get-compatibility-func' need some extra
> pizzazz to favor the prefixed form for certain versions? Because, as
> shown, something like (erc-jason-parse-string "42") would still signal a
> `json-parse-error' on Emacs 27, no?)

Yes, you are right, I could imagine using an optional argument to
indicate a minimal version.

>>> But in ERC's case, there'd be no avoiding this kind of indirection.
>>> (Please correct me if that's a flawed understanding.)
>>
>> While prefixing is used, no, because we cannot assume that compat is
>> installed.
>
> Right. Makes sense.
>
> So, getting back to the main thrust of this thread, I guess I'll go
> ahead and add the proposed changes to Emacs 29, barring any last-minute
> objections. Thanks.

If there are no technical objects, I think the only thing that could be
added would be a comment explaining why compat is used or linking to
this thread.?