Reporting error to user...

Reporting error to user...

[Oleksandr Gavenko]

I wrote blogging program in Elisp and have to report errors to users (when
required file not found or network authorisation failed).

How to report error to users?

I think that showing *Backtrace* buffer from '(error ...)' is not good way to
do this (I have filling that such behavior indicates bug or "not yet
implemented" condition in program).

(message "...") is better but sometimes another modes hide minibufer text
(like semantic when showing symbol type).

Would like to hear suggestions...

-- 
Best regards!

Re: Reporting error to user...

[Jambunathan K]

Last couple of sentences down below may interest you.

,---- From (info "(elisp) Signaling Errors")
|
|  -- Function: user-error format-string &rest args
|      This function behaves exactly like `error', except that it uses
|      the error symbol `user-error' rather than `error'.  As the name
|      suggests, this is intended to report errors on the part of the
|      user, rather than errors in the code itself.  For example, if you
|      try to use the command `Info-history-back' (`l') to move back
|      beyond the start of your Info browsing history, Emacs signals a
|      `user-error'.  Such errors do not cause entry to the debugger,
|      even when `debug-on-error' is non-`nil'.  *Note Error
|      Debugging::.
|
`----

Oleksandr Gavenko <gavenkoa@gmail.com> writes:

> I wrote blogging program in Elisp and have to report errors to users (when
> required file not found or network authorisation failed).
>
> How to report error to users?
>
> I think that showing *Backtrace* buffer from '(error ...)' is not good way to
> do this (I have filling that such behavior indicates bug or "not yet
> implemented" condition in program).
>
> (message "...") is better but sometimes another modes hide minibufer text
> (like semantic when showing symbol type).
>
> Would like to hear suggestions...

-- 

Re: Reporting error to user...

[Oleksandr Gavenko]

On 2013-03-03, Jambunathan K wrote:

> Oleksandr Gavenko <gavenkoa@gmail.com> writes:
>
>> I wrote blogging program in Elisp and have to report errors to users (when
>> required file not found or network authorisation failed).
>>
>> How to report error to users?
>>
>> I think that showing *Backtrace* buffer from '(error ...)' is not good way to
>> do this (I have filling that such behavior indicates bug or "not yet
>> implemented" condition in program).
>>
>> (message "...") is better but sometimes another modes hide minibufer text
>> (like semantic when showing symbol type).
>>
>> Would like to hear suggestions...
>
> Last couple of sentences down below may interest you.
>
> ,---- From (info "(elisp) Signaling Errors")
> |
> |  -- Function: user-error format-string &rest args
> |      This function behaves exactly like `error', except that it uses
> |      the error symbol `user-error' rather than `error'.  As the name
> |      suggests, this is intended to report errors on the part of the
> |      user, rather than errors in the code itself.  For example, if you
> |      try to use the command `Info-history-back' (`l') to move back
> |      beyond the start of your Info browsing history, Emacs signals a
> |      `user-error'.  Such errors do not cause entry to the debugger,
> |      even when `debug-on-error' is non-`nil'.  *Note Error
> |      Debugging::.
> |
> `----

Hm... (describe-function 'user-error) return (void-function user-error).

I use Emacs 24.2.1.


From bzr repo:

  2012-05-04  Stefan Monnier  <monnier@...>

      * data.c (PUT_ERROR): New macro.
      (syms_of_data): Use it.  Add new error type `user-error'.

Build from trunk beep and show error message in minibuffer on 'user-error'.


How to backport 'user-error' into early Emacs versions? Do I need to write
a wrapper:

  (defun my-user-error (format &rest args)
    (if (fboundp 'user-error))
         (apply 'user-error format args)
       (apply 'error format args))

in my mode and use 'my-user-error' instead if 'user-error'?

-- 
Best regards!

Re: Reporting error to user...

[Dmitry Gutov]

Oleksandr Gavenko <gavenkoa@gmail.com> writes:
> How to backport 'user-error' into early Emacs versions? Do I need to write
> a wrapper:
>
>   (defun my-user-error (format &rest args)
>     (if (fboundp 'user-error))
>          (apply 'user-error format args)
>        (apply 'error format args))
>
> in my mode and use 'my-user-error' instead if 'user-error'?

You can just copy the implementation, it's trivial.

Re: Reporting error to user...

[Oleksandr Gavenko]

On 2013-03-05, Dmitry Gutov wrote:

> Oleksandr Gavenko <gavenkoa@gmail.com> writes:
>> How to backport 'user-error' into early Emacs versions? Do I need to write
>> a wrapper:
>>
>>   (defun my-user-error (format &rest args)
>>     (if (fboundp 'user-error))
>>          (apply 'user-error format args)
>>        (apply 'error format args))
>>
>> in my mode and use 'my-user-error' instead if 'user-error'?
>
> You can just copy the implementation, it's trivial.
>
While implementation is trivial (from 'emacs-bzr/trunk/lisp/subr.el'):

  (defun user-error (format &rest args)
    (while t
      (signal 'user-error (list (apply #'format format args)))))

I eval: (symbol-plist 'user-error) and get:

  (error-conditions (user-error error) error-message "")

But I can't find a place which put 'error-conditions' to 'user-error' symbol.

Really this must be done, from 'signal' docs:

     The argument ERROR-SYMBOL must be an "error symbol"--a symbol
     bearing a property `error-conditions' whose value is a list of
     condition names.

-- 
Best regards!