Re: Making debugging possible on expressions executed from ielm

["Jarosław Rzeszótko" <jrzeszotko@gmail.com>]

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Any chances of getting this patch committed?

Thanks and cheers,
Jarosław Rzeszótko

On Mon, Jan 15, 2018 at 8:22 PM, Jarosław Rzeszótko <jrzeszotko@gmail.com>
wrote:

> Stefan,
>
> I did not know about condition-case-unless-debug, it indeed does make
> debugging possible with a simpler change and without any side effects. I
> attach the patch.
>
> Cheers,
> Jarosław Rzeszótko
>
> On Sat, Jan 13, 2018 at 10:22 AM, Jarosław Rzeszótko <jrzeszotko@gmail.com
> > wrote:
>
>> I attach a patch for ielm.el that makes it possible to enter the debugger
>> when executing expressions in ielm, and that makes ielm respect the
>> debug-on-error and debug-on-exit flags.
>>
>> I guess that possibly the reason that was not originally done is that it
>> is not obvious how to restore ielm to a usable state after the debugger has
>> been entered. My patch makes use of the fact that unwind-protect unwind
>> forms are still executed when user resumes execution from the debugger
>> after an error.
>>
>> Without the patch, ielm wraps the evaluation of the expression given by
>> the user in a condition case, and in case of an error, or exit, displays an
>> appropriate message in its buffer, right under the evaluated expression,
>> regardless of debug-on-error and debug-on-exit.
>>
>> With the patch, the message that ielm displays in its buffer will be a
>> generic error message  regardless if there was an error in the evaluated
>> form, or a quit. However:
>>
>> - if debug-on-error is t, emacs will enter the debugger and show a stack
>> trace, just like with almost any other evaluation method. When the user
>> continues the execution from the debugger, ielm will correctly resume
>> execution
>>
>> - if debug-on-error is nil, emacs will display the specific error in the
>> minibuffer anyway
>>
>> Similar things are true for debug-on-quit.
>>
>> I think this is an improvement over the current state of affairs. Of
>> course ideally I would like to preserve the "nice" message in ielm buffer
>> and make the improvements I made, but emacs does not seem to make it
>> possible to do some handling of an error and then to re-raise it while
>> preserving the original stack trace.
>>
>> Cheers,
>> Jarosław Rzeszótko
>>
>>
>>
>

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