Re: Problem with let/cl-letf binding stuff with org-capture

[Arthur Miller <arthur.miller@live.com>]

Ruijie Yu <ruijie@netyu.xyz> writes:

> Hi Arthur,
>
> Please excuse my brevity and semi-random line of thought, as I’m replying on mobile right now.  See below. 
>
>> On Feb 10, 2023, at 23:11, Arthur Miller <arthur.miller@live.com> wrote:
>> 
>> 
>> Based on a Reddit thread:
>> 
>> https://www.reddit.com/r/emacs/comments/10xhvd8/a_little_readstring_utility_using_an_org_mode/j7xziao/?context=3
>> 
>> I did a small experiment to see if I can re-use org-capture, to just capture a
>> string from a buffer, without actually writing to any file.
>> 
>> My plan was to just let-bind org-capture-finalize with cl-letf:
>> 
>> #+begin_src emacs-lisp
>> (defun my-read-string ()
>> (cl-letf (((symbol-function 'org-capture-finalize) ;; C-c C-c
>>           (lambda (&optional _) (interactive "P") (buffer-string)))
>>          ((symbol-function 'org-kill-note-or-show-branches) #'kill-buffer)) ;; C-c C-k
>>  (let ((org-capture-templates '(("s" "string" plain (function ignore)))))
>>    (org-capture nil "s"))))
>> #+end_src
>
> Based on my somewhat-limited experience with CL (and elisp), I have never seen
> this particular type of letf structure.  What I am used to seeing and writing is
> the following:

It uses "place" or "field" to set the symbol binding, as in setf or incf.

You can read more on SX:

https://stackoverflow.com/questions/39550578/in-emacs-what-is-the-difference-between-cl-flet-and-cl-letf

> (cl-letf ((f (x) (1+ x))
>    (1+ (f 2)))
> ; => 4
>
> In particular, IIUC, I don’t think you would need symbol-function here.  Maybe
> you can learn more from the docstring of cl-letf than me trying to drain my
> memory on this topic without reference.
>
> Also, in the code snippet you provided, what *should* org-capture-finalize be?  A function that can be called like this:
>
>    (org-capture-finalize arg1 arg2)
>
> ? Or a variable containing a function (reference) that can be called like this:
>
>    (funcall org-capture-finalize arg1 arg2)
>
> ?  In the former case you might be able to use cl-letf, and in the latter case you should use let with a lambda value. 
>
>> Unfortunately, that does not work. Regardless of binding, and if I used cl-letf
>> or cl-flet or cl-labels, or old let, or something brewed on the internet, the
>> binding org-capture see for org-capture-finalize, is the original one from
>> org-capture.el.
>> 
>> My second experiment was to abstract the finalize function into a funcallable
>> fariable in org-capture.el (I have patched org-capture.el with this):
>> 
>> #+begin_src emacs-lisp
>> (defvar org-capture-finalizer #'org-capture--default-finalize)
>> 
>> (defun org-capture-finalize (&optional stay-with-capture)
>> "Finalize the capture process.
>> With prefix argument STAY-WITH-CAPTURE, jump to the location of the
>> captured item after finalizing."
>> (interactive "P")
>> (funcall org-capture-finalizer stay-with-capture))
>> 
>> 
>> (defun org-capture--default-finalize (&optional stay-with-capture)
>> "Default implementation for org-capture finalizer function."
>> 
>> ;; this is the original org-capture-finalize just renamed to "default-finalize"
>> )
>> #+end_src
>> 
>> So I could then have something like this (never mind C-c C-k function being
>> removed):
>> 
>> #+begin_src emacs-lisp
>> (defun my-read-string ()
>> (let ((org-capture-templates '(("s" "string" plain (function ignore))))
>>      (org-capture-finalizer
>>       (lambda (&optional _) (interactive "P") (buffer-string))))
>>  (org-capture nil "s")))
>> #+end_src
>> 
>> However I see that the binding for the org-capture-finalizer, in capture buffer,
>> is still the default 'org-capture--default-finalize' and not my lambda.
>
> I guess this answers part of my question in my previous paragraph.  Is
> org-capture-finalizer defined via defvar?  If so, does it help if you put an
> empty defvar before the let binding?  If not, maybe someone actually using Emacs
> right now can be of more help here.

These were two different examples; one that let-binds the function
'org-caputre-finalize', via cl-letf and the latter one that was completely
different in which I have defvared a symbol so I can let-bind it as a variable.

>                                       If not, maybe someone actually using Emacs
> right now can be of more help here.

Don't worry; thanks for the help anyway!

/a