Function behaves differently when debugged

Function behaves differently when debugged

[Matthias Pfeifer]

Hi everybody,

I have this function

(defun mp-ibuffer-show-file-path ()
  (interactive)
   (let ((buf (ibuffer-current-buffer))
        (lsoutput nil))
    (if (not (null buf))
        (when (file-exists-p (buffer-file-name buf))
          (with-temp-buffer
            (let* ((filename (buffer-file-name buf))
                   (file-directory (file-name-directory filename))
                   (just-filename (file-name-nondirectory filename)))
              (setq lsoutput file-directory))))
      (setq lsoutput "Buffer is not backed by a file"))
    (message lsoutput)))

I bind it to some key in ibuffer-mode. it should print the path to a
buffer's file. When point is on a line of a buffer that is not backed by a
file (eg *Messages*) then i get this output:

wrong type argument: strinp, nil

However when I instantiated my defun for debugging and do the same again I
get

"Buffer is not backed by a file"

The second behavior is actually what i had expected when i was writing the
function. The first behavior is a bit unexpected. Also I do not understand
why my function behaves differently when my defun is debugged and when it
run without debugging.


Thanks for your help.


Matthias

Re: Function behaves differently when debugged

[Ralf Fassel]

* Matthias Pfeifer <pfemat@web.de>
| I bind it to some key in ibuffer-mode. it should print the path to a
| buffer's file. When point is on a line of a buffer that is not backed by a
| file (eg *Messages*) then i get this output:
>
| wrong type argument: strinp, nil

You could set the variable debug-on-error to t to see where the error
occurs and protect that function call by 'stringp'.

| Also I do not understand why my function behaves differently when my
| defun is debugged and when it run without debugging.

Probably because the current buffer query function does not return
'nil' when you are in the debugging console...

HTH
R'

Re: Function behaves differently when debugged

[Robert L.]

On 5/14/2018, Matthias Pfeifer wrote:

> Hi everybody,
> 
> I have this function
> 
> (defun mp-ibuffer-show-file-path ()
>   (interactive)
>    (let ((buf (ibuffer-current-buffer))
>         (lsoutput nil))
>     (if (not (null buf))
>         (when (file-exists-p (buffer-file-name buf))
>           (with-temp-buffer
>             (let* ((filename (buffer-file-name buf))
>                    (file-directory (file-name-directory filename))
>                    (just-filename (file-name-nondirectory filename)))
>               (setq lsoutput file-directory))))
>       (setq lsoutput "Buffer is not backed by a file"))
>     (message lsoutput)))
> 
> I bind it to some key in ibuffer-mode. it should print the path to a
> buffer's file. When point is on a line of a buffer that is not backed by a
> file (eg Messages) then i get this output:
> 
> wrong type argument: strinp, nil
> 
> However when I instantiated my defun for debugging and do the same again I
> get
> 
> "Buffer is not backed by a file"
> 
> The second behavior is actually what i had expected when i was writing the
> function. The first behavior is a bit unexpected. Also I do not understand
> why my function behaves differently when my defun is debugged and when it
> run without debugging.

Untested.

(defun mp-ibuffer-show-file-path ()
  (interactive)
  (let ((buf (ibuffer-current-buffer))
        (lsoutput "Buffer is not backed by a file"))
    (when buf
      (let ((filename (buffer-file-name buf)))
        (when (and filename (file-exists-p filename))
          (with-temp-buffer
            (let* ((file-directory (file-name-directory filename))
                   (just-filename (file-name-nondirectory filename)))
              (setq lsoutput file-directory))))))
    (message lsoutput)))

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