Re: Capture template and elisp expression

[Rainer M Krug <r.m.krug@gmail.com>]

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On 01/07/2011 03:14 PM, Carsten Dominik wrote:
> 
> On Jan 7, 2011, at 1:08 PM, Štěpán Němec wrote:
> 
>> Carsten Dominik <carsten.dominik@gmail.com> writes:
>>
>>> On Jan 6, 2011, at 11:26 PM, Nick Dokos wrote:
>>>
>>>> Rainer M Krug <r.m.krug@gmail.com> wrote:
>>>>
>>>>>
>>>>> Hi
>>>>>
>>>>> I want to use a Capture Template to record changes to files under
>>>>> version control. Everything works as expected, but I would like to
>>>>> include the current revision in the template.
>>>>>
>>>>> Therefore I tried the following:
>>>>>
>>>>> * %T %? at %a by Rainer M Krug, email: Rainer@krugs.de
>>>>> %(vc-working-revision buffer-file-name)
>>>>>
>>>>> for the template, but I get an error:
>>>>>
>>>>> **** <2011-01-06 Thu 13:06>  at
>>>>> [[file:~/Documents/Projects/BiocontrolAndAlienDynamics/
>>>>> nonSpatialAcacia/trunc/R/nsa.org::*Finalise][Finalise]]
>>>>> by Rainer M Krug, email: Rainer@krugs.de %![Error: (wrong-type-
>>>>> argument
>>>>> stringp nil)]
>>>>>
>>>>> Any idea how I could get the revision of the org file from which the
>>>>> Capture has been initiated (here
>>>>> ~/Documents/Projects/BiocontrolAndAlienDynamics/nonSpatialAcacia/
>>>>> trunc/R/nsa.org
>>>>> )?
>>>>>
>>>>
>>>> There are a few problems: the evaluation of the sexp happens in the
>>>> capture buffer where buffer-file-name returns nil. Even if you could
>>>> get the file name, vc-working-revision would return nil on a file that
>>>> is not VC-registered and the template would barf.
>>>>
>>>> Those are easy problems to solve but there is another one that seems
>>>> insurmountable (with current code): my original thought was to use the
>>>> %a escape to pass the link to a lisp function, extract the file name
>>>> from it[fn:1] and run vc-working-revision on it (with appropriate
>>>> safeguards
>>>> to catch non-VC files), something like this:
>>>>
>>>> "* %T %? at %a by Rainer M Krug, email: Rainer@krugs.de        %(rk-
>>>> custom-function-to-get-vc-revision \"%a\")"
>>>>
>>>> However, this fails because at the time that %(sexp) constructs are
>>>> expanded, simple %a etc. constructs have not been expanded yet, so what
>>>> the function above gets is a literal "%a": the subtitution sequence is
>>>>
>>>>           ;; %[] Insert contents of a file.
>>>>
>>>>           ...
>>>>
>>>>           ;; %() embedded elisp
>>>>
>>>>           ...
>>>>
>>>>           ;; Simple %-escapes
>>>>
>>>> (see lisp/org-capture.el, lines 1181-1229 or so).
>>>>
>>>> Moreover, this sequence was different and was changed deliberately (see
>>>> the thread http://thread.gmane.org/gmane.emacs.orgmode/27649), so if it
>>>> is changed back, Sebastion Rose will not be happy :-)
>>>>
>>>> So it seems there is no way to pass values from the capture context
>>>> to a
>>>> lisp function in the capture template, but maybe I'm missing something.
>>>>
>>>> Thanks,
>>>> Nick
>>>>
>>>> Footnotes:
>>>> [fn:1] Is there an easier way to get the filename of the file I was
>>>> visiting when I initiated the capture? If not, should there be? Perhaps
>>>> a %f escape?
>>>
>>> Hi Nick,
>>>
>>> you can use
>>>
>>>    (buffer-file-name (org-capture-get :original-buffer))
>>>
>>> and we could certainly introduce a special escape for it if helpful.
>>>
>>> If it is easier, we can also put the filename itself into the
>>> property list,
>>> and any other information we like.  This should happen in the function
>>> org-capture,
>>> close to the location where the buffer is stored, so near this line:
>>>
>>>     (org-capture-put :original-buffer orig-buf :annotation annotation
>>>              :initial initial)
>>>
>>> org-capture uses this property list precisely so that it is simple
>>> to add any information required.
>>>
>>> Note that, after the template has been filled in, it is better
>>> to access information in the property list with
>>>
>>>
>>>  (org-capture-get PROPERTY 'local)
>>>
>>> to avoid conflicts with other ongoing capture processes.
>>>
>>> Hope this helps.
>>
>> Why aren't the %() expressions simply evaluated in the original buffer
>> (if available)? That would solve these issues in a general way. It seems
>> to me that there is no advantage to evaluating the expressions in the
>> temporary capture buffer, but I'm not familiar with the code so I might
>> be missing something. Is there a reason for that?
> 
> The sexp can be used to insert stuff into the template, so I think it
> is correct to evaluate it in the template buffer.

Just an idea - as you said, it makes sense to evaluate it in the
template buffer. But, if it is technically nod difficult, what about
adding an additional escape, e.g.

%ob(sexp)

for which sexp is evaluated in the original buffer, from which capture
is called? in that way, many problems could be solved with a minimum of
effort.

Cheers,

Rainer


> 
> - Carsten


- -- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation
Biology, UCT), Dipl. Phys. (Germany)

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