[babel] VC-Log does not run correctly

[babel] VC-Log does not run correctly

[Sebastien Vauban]

#+TITLE:     Last VC Log
#+AUTHOR:    Seb Vauban
#+DATE:      2011-09-08
#+LANGUAGE:  en
#+OPTIONS:   num:nil toc:nil

* Abstract

I'm trying to get, from the VC backend (currently SVN in my case), the name
and date of the last committer. Eventually, as well the last log message.

Therefore, I try to use the =vc-log= function in the Library of Babel, copied
back in this buffer, for the sake of simplicity.

When calling =C-c C-e b= on this buffer, I get asked by Emacs:

    "Buffer has a running process; kill it? (yes or no)"

- If I don't say anything, the export process is just hanging in the blue...

- If I say yes, the export process really begins, but there is no vc log
  inserted where I expect it.

- Exactly the same (as if I say yes) happens if I say no: export goes on, but
  no vc log!

What could go wrong here?

* Org Source

#+source: vc-log
#+headers: :var limit=-1
#+headers: :var buf=(buffer-name (current-buffer))
#+begin_src emacs-lisp :exports none
  ;; Most of this code is copied from vc.el vc-print-log
  (require 'vc)
  (when (vc-find-backend-function
         (vc-backend (buffer-file-name (get-buffer buf))) 'print-log)
    (let ((limit -1)
          (vc-fileset nil)
          (backend nil)
          (files nil))
      (with-current-buffer (get-buffer buf)
        (setq vc-fileset (vc-deduce-fileset t)) ; FIXME: Why t? --Stef
        (setq backend (car vc-fileset))
        (setq files (cadr vc-fileset)))
      (with-temp-buffer 
        (let ((status (vc-call-backend
                       backend 'print-log files (current-buffer))))
          (when (and (processp status)   ; Make sure status is a process
                     (= 0 (process-exit-status status))) ; which has not terminated
            (while (not (eq 'exit (process-status status)))
              (sit-for 1 t)))
          (buffer-string)))))
#+end_src

Last edited by XXX on XXX

#+call: vc-log()

* HTML Result

#+begin_src html
Last VC Log
Org Source

Last edited by XXX on XXX

Working file: c:/home/sva/ecm.org

Date: 2011-09-08

Author: Seb Vauban
Validate XHTML 1.0
#+end_src

As you can see, there is no vc log at all, well the header of the vc log
buffer:

    "Working file: c:/home/sva/ecm.org"

* Messages buffer

#+begin_src text
Export buffer: 
Exporting...
Running svn status -v ecm.html in foreground...
Running svn status -v ecm.html...OK = 0
Position saved to mark ring, go back with M-x org-mark-ring-goto.
(info) +-> Requiring `help-fns'... already loaded [6 times]
executing Emacs-Lisp code block (vc-log)...

(buf (quote "ecm.org"))

(limit (quote -1))

Running svn log -rHEAD:0 ecm.org in background... done
"Working file: c:/home/sva/ecm.org
"
(info) +-> Requiring `help-fns'... already loaded
executing Emacs-Lisp code block...

(results (quote "Working file: c:/home/sva/ecm.org
"))

Code block evaluation complete.
org-babel-exp processing...
org-babel-exp processing...
Exporting...
Saving file c:/home/sva/ecm.html...
Wrote c:/home/sva/ecm.html
Running svn status -v ecm.html in foreground...
Running svn status -v ecm.html...OK = 0
Exporting... done
#+end_src

Any idea on how to help me going further with this?

Best regards,
  Seb

-- 
Sebastien Vauban

Re: [babel] VC-Log does not run correctly

[Eric Schulte]

Hi Seb,

Off the top of my head I would recommend first running the vc-log code
block interactively to see how it behaves, then possibly expanding the
code block with C-c C-v v, copying the results to your scratch buffer,
evaluating the resulting elisp with edebug (C-M-x with a prefix
argument), which will then allow you to step through the code execution
statement by statement.  This should help to pinpoint the problem.

Hope this helps -- Eric

"Sebastien Vauban" <wxhgmqzgwmuf@spammotel.com> writes:

> #+TITLE:     Last VC Log
> #+AUTHOR:    Seb Vauban
> #+DATE:      2011-09-08
> #+LANGUAGE:  en
> #+OPTIONS:   num:nil toc:nil
>
> * Abstract
>
> I'm trying to get, from the VC backend (currently SVN in my case), the name
> and date of the last committer. Eventually, as well the last log message.
>
> Therefore, I try to use the =vc-log= function in the Library of Babel, copied
> back in this buffer, for the sake of simplicity.
>
> When calling =C-c C-e b= on this buffer, I get asked by Emacs:
>
>     "Buffer has a running process; kill it? (yes or no)"
>
> - If I don't say anything, the export process is just hanging in the blue...
>
> - If I say yes, the export process really begins, but there is no vc log
>   inserted where I expect it.
>
> - Exactly the same (as if I say yes) happens if I say no: export goes on, but
>   no vc log!
>
> What could go wrong here?
>
> * Org Source
>
> #+source: vc-log
> #+headers: :var limit=-1
> #+headers: :var buf=(buffer-name (current-buffer))
> #+begin_src emacs-lisp :exports none
>   ;; Most of this code is copied from vc.el vc-print-log
>   (require 'vc)
>   (when (vc-find-backend-function
>          (vc-backend (buffer-file-name (get-buffer buf))) 'print-log)
>     (let ((limit -1)
>           (vc-fileset nil)
>           (backend nil)
>           (files nil))
>       (with-current-buffer (get-buffer buf)
>         (setq vc-fileset (vc-deduce-fileset t)) ; FIXME: Why t? --Stef
>         (setq backend (car vc-fileset))
>         (setq files (cadr vc-fileset)))
>       (with-temp-buffer 
>         (let ((status (vc-call-backend
>                        backend 'print-log files (current-buffer))))
>           (when (and (processp status)   ; Make sure status is a process
>                      (= 0 (process-exit-status status))) ; which has not terminated
>             (while (not (eq 'exit (process-status status)))
>               (sit-for 1 t)))
>           (buffer-string)))))
> #+end_src
>
> Last edited by XXX on XXX
>
> #+call: vc-log()
>
> * HTML Result
>
> #+begin_src html
> Last VC Log
> Org Source
>
> Last edited by XXX on XXX
>
> Working file: c:/home/sva/ecm.org
>
> Date: 2011-09-08
>
> Author: Seb Vauban
> Validate XHTML 1.0
> #+end_src
>
> As you can see, there is no vc log at all, well the header of the vc log
> buffer:
>
>     "Working file: c:/home/sva/ecm.org"
>
> * Messages buffer
>
> #+begin_src text
> Export buffer: 
> Exporting...
> Running svn status -v ecm.html in foreground...
> Running svn status -v ecm.html...OK = 0
> Position saved to mark ring, go back with M-x org-mark-ring-goto.
> (info) +-> Requiring `help-fns'... already loaded [6 times]
> executing Emacs-Lisp code block (vc-log)...
>
> (buf (quote "ecm.org"))
>
> (limit (quote -1))
>
> Running svn log -rHEAD:0 ecm.org in background... done
> "Working file: c:/home/sva/ecm.org
> "
> (info) +-> Requiring `help-fns'... already loaded
> executing Emacs-Lisp code block...
>
> (results (quote "Working file: c:/home/sva/ecm.org
> "))
>
> Code block evaluation complete.
> org-babel-exp processing...
> org-babel-exp processing...
> Exporting...
> Saving file c:/home/sva/ecm.html...
> Wrote c:/home/sva/ecm.html
> Running svn status -v ecm.html in foreground...
> Running svn status -v ecm.html...OK = 0
> Exporting... done
> #+end_src
>
> Any idea on how to help me going further with this?
>
> Best regards,
>   Seb

-- 
Eric Schulte
http://cs.unm.edu/~eschulte/

Re: [babel] VC-Log does not run correctly

[Sebastien Vauban]

Hi Eric,

Eric Schulte wrote:
> Off the top of my head I would recommend first running the vc-log code
> block interactively to see how it behaves

Had alreayd done it. Same behavior: question asked; whichever the answer, the
results is empty (well, almost: only the first line stating the name of the file).

> then possibly expanding the code block with C-c C-v v, copying the results
> to your scratch buffer, evaluating the resulting elisp with edebug (C-M-x
> with a prefix argument), which will then allow you to step through the code
> execution statement by statement. This should help to pinpoint the problem.

#+begin_src emacs-lisp
(let ((buf (quote "ecm-org.txt"))
      (limit (quote -1)))
  ;; Most of this code is copied from vc.el vc-print-log
  (require 'vc)
  (when (vc-find-backend-function
         (vc-backend (buffer-file-name (get-buffer buf))) 'print-log)
    (let ((limit -1)
          (vc-fileset nil)
          (backend nil)
          (files nil))
      (with-current-buffer (get-buffer buf)
        (setq vc-fileset (vc-deduce-fileset t)) ; FIXME: Why t? --Stef
        (setq backend (car vc-fileset))
        (setq files (cadr vc-fileset)))
      (with-temp-buffer 
        (let ((status (vc-call-backend
                       backend 'print-log files (current-buffer))))
          (when (and (processp status)   ; Make sure status is a process
                     (= 0 (process-exit-status status))) ; which has not terminated
            (while (not (eq 'exit (process-status status)))
              (sit-for 1 t)))
          (buffer-string))))))
#+end_src

The first 2 lines were added.

Executing that block gives the same results. However, I still need to do your
next piece of advice: going through an edebug. I'll do it, and will let you
know.

Best regards,
  Seb

-- 
Sebastien Vauban

Re: [babel] VC-Log does not run correctly

[Sebastien Vauban]

Hi Eric and all,

Eric Schulte wrote:
>> When calling =C-c C-e b= on this buffer, I get asked by Emacs:
>>
>>     "Buffer has a running process; kill it? (yes or no)"
>>
>> - If I don't say anything, the export process is just hanging in the blue...
>>
>> - If I say yes, the export process really begins, but there is no vc log
>>   inserted where I expect it.
>>
>> - Exactly the same (as if I say yes) happens if I say no: export goes on, but
>>   no vc log!
>>
>> What could go wrong here?
>>
>> * Org Source
>>
>> #+source: vc-log
>> #+headers: :var limit=-1
>> #+headers: :var buf=(buffer-name (current-buffer))
>> #+begin_src emacs-lisp :exports none
>>   ;; Most of this code is copied from vc.el vc-print-log
>>   (require 'vc)
>>   (when (vc-find-backend-function
>>          (vc-backend (buffer-file-name (get-buffer buf))) 'print-log)
>>     (let ((limit -1)
>>           (vc-fileset nil)
>>           (backend nil)
>>           (files nil))
>>       (with-current-buffer (get-buffer buf)
>>         (setq vc-fileset (vc-deduce-fileset t)) ; FIXME: Why t? --Stef
>>         (setq backend (car vc-fileset))
>>         (setq files (cadr vc-fileset)))
>>       (with-temp-buffer 
>>         (let ((status (vc-call-backend
>>                        backend 'print-log files (current-buffer))))
>>           (when (and (processp status)   ; Make sure status is a process
>>                      (= 0 (process-exit-status status))) ; which has not terminated
>>             (while (not (eq 'exit (process-status status)))
>>               (sit-for 1 t)))
>>           (buffer-string)))))
>> #+end_src
>
> Off the top of my head I would recommend

Thanks for this clear TODO list, which has giving me some interesting
returns...

> first running the vc-log code block interactively to see how it behaves,

As previously said, that worked OK.

> then possibly expanding the code block with C-c C-v v,

The values in the preamble of the expanded block do look OK (see next
section).

> copying the results to your scratch buffer, evaluating the resulting elisp
> with edebug (C-M-x with a prefix argument), which will then allow you to
> step through the code execution statement by statement.

Did this on the following contents in the scratch buffer:

#+begin_src emacs-lisp
(let ((buf (quote "ecm-vc-log.txt"))
      (limit (quote -1)))
  ;; Most of this code is copied from vc.el vc-print-log
  (require 'vc)
  (when (vc-find-backend-function
         (vc-backend (buffer-file-name (get-buffer buf))) 'print-log)
    (let ((limit -1)
          (vc-fileset nil)
          (backend nil)
          (files nil))
      (with-current-buffer (get-buffer buf)
        (setq vc-fileset (vc-deduce-fileset t)) ; FIXME: Why t? --Stef
        (setq backend (car vc-fileset))
        (setq files (cadr vc-fileset)))
      (with-temp-buffer 
        (let ((status (vc-call-backend
                       backend 'print-log files (current-buffer))))
          (when (and (processp status)   ; Make sure status is a process
                     (= 0 (process-exit-status status))) ; which has not terminated
            (while (not (eq 'exit (process-status status)))
              (sit-for 1 t)))
          (buffer-string))))))
#+end_src

... and it works OK as well. I mean: when I trace the code manually (with
SPC), I do get the correct (thus, full) log history printed in the echo area,
when I arrive at the last lines of this block's execution.

All the vars were as well correctly resolved:
- backend is SVN
- file is a full path to the right location
- etc.

So, there is a difference between:
- executing this code in the scratch buffer, step by step, versus
- executing it in a #+call line

However, these instructions helped me a lot. For example, I've observed that,
in the scratch buffer, C-x C-e doesn't run in the intended way: I also have
the question arising, about the running process.

And this is somehow related to the process returning something, or being still
alive. ...Here begins my point of incompetence...

But, by playing around, I've managed to fix the code so that it now works OK
in my Org buffer.

Working code:

#+source: vc-log
#+headers: :var limit=-1
#+headers: :var buf=(buffer-name (current-buffer))
#+begin_src emacs-lisp :exports none
  ;; Most of this code is copied from vc.el vc-print-log
  (require 'vc)
  (when (vc-find-backend-function
         (vc-backend (buffer-file-name (get-buffer buf))) 'print-log)
    (let ((limit -1)
          (vc-fileset nil)
          (backend nil)
          (files nil))
      (with-current-buffer (get-buffer buf)
        (setq vc-fileset (vc-deduce-fileset t)) ; FIXME: Why t? --Stef
        (setq backend (car vc-fileset))
        (setq files (cadr vc-fileset)))
      (with-temp-buffer 
        (let ((status (vc-call-backend
                       backend 'print-log files (current-buffer))))
          (when (and t ; (processp status)   ; Make sure status is a process
                     ;; (= 0 (process-exit-status status)) ; which has not terminated
                     )
             ;; (while (not (eq 'exit (process-status status)))
              (sit-for 1 t)
               ;; )
            )
          (buffer-string)))))
#+end_src

To get it working, I have had to fix 2 things (to the original version of
vc-log, in the LOB):

1. comment the `and' condition: the lines with `processp status' and
   `process-exit-status' (adding a `t' value to make it success)

   If I don't do that, I do have the question "Buffer has a running process"
   arising... and no results displayed.

2. comment the `while' condition: the line with `process-status'

   If I don't do that, I've the error "edebug-signal: Buffer *temp*<1> has no
   process", and no results displayed.

Finally, to be complete, I've played with the value of the wait timer
(`sit-for'):

- greater or equal to 1 works OK, but delays the execution for that amount of
  time, of course.

- equal to 0, gets me back to the question arising, about "Buffer has a
  running process".

Voilà, there it is. I can't say more about the strange things appearing here.
But I'm willing to answer any question to further test this.

I'm happy to have a workaround, but would be glad someone could help into
making this code chunk robust on all Org platforms, as I guess what I've done
is quite fragile...

Best regards,
  Seb

-- 
Sebastien Vauban

Re: [babel] VC-Log does not run correctly

[suvayu ali]

Hi Seb,

On Thu, Sep 8, 2011 at 4:16 PM, Sebastien Vauban
<wxhgmqzgwmuf@spammotel.com> wrote:
>  (when (vc-find-backend-function
>         (vc-backend (buffer-file-name (get-buffer buf))) 'print-log)
>

AFAIU from a previous issue (more than a year back I think), you need
to ensure buffer-file-name returns  something reasonable. The problem
is if it is evaluated in a temporary buffer (is that the case during
export?) then it will return nil which confuses vc.

Hope this helps.

-- 
Suvayu

Open source is the future. It sets us free.