Re: [O] [babel] Export problem (Wrong type argument: consp, nil)

[Sebastien Vauban]

Hi Eric,

Eric Schulte wrote:
> "Sebastien Vauban" <address@hidden> writes:
>> If there is no value assigned to the code block...
>> ... there is no an error when exporting:
>>
>> #+begin_src text
>> Debugger entered--Lisp error: (wrong-type-argument consp nil)
>>   setcdr(nil "nil=x")
>> #+end_src
>
> All variables must be given a default value, which is why it is an error
> to write a code block like the following.
>
> #+source: circle(x)
> #+begin_src python
> return x*x
> #+end_src
>
> I've just pushed up a change which provides a better error message in
> this case.

It works OK. Thanks a lot for that.

Remark: This did correct a problem that I had with my local LOB, and which
appeared a couple of months ago. I tried to find the post back, but I
couldn't. At that time, you tried my example, but you couldn't reproduce it.
Anyway, I now could check that it was because of this, now that the message is
a lot clearer than "consp, nil".

Question: Would it be possible to add the src-name in the error message?  You
know, in my LOB, I have so many times the same var name coming back again,
that having the name of the source block would be of a great help. I tried
looking into the code to see if I could do it myself, but I must admit it's
still too hard for me. I have the impression many functions must be extended
in order to pass the src-name down to where the error is thrown...

Other thing, I tried to add a test for checking your fix never will be
regressed. This is what I currently have:

* Does not work
  :PROPERTIES:
  :ID:       f2df5ba6-75fa-4e6b-8441-65ed84963627
  :END:

If there is no value assigned to the code block, a proper error should be
thrown.

#+source: carre(x)
#+begin_src python
return x*x
#+end_src

* Test

#+begin_src emacs-lisp
(ert-deftest test-org-babel/no-defaut-value-for-var ()
  "Test that the absence of a default value for a variable does throw a proper
  error."
  (org-test-at-id "f2df5ba6-75fa-4e6b-8441-65ed84963627"
    (org-babel-next-src-block)
    (should-error (org-babel-execute-src-block))
    :type 'error))
#+end_src

Though, I have 2 questions:

- How can I differentiate between the clean error (with a message) and the one
  which wasn't correctly trapped?  Based on the first line of a backtrace
  (string comparison) or on the type of the error?  In the latter case, how
  can I know what's the type of the current error thrown, and the one of the
  error before your fix?

- I wonder why we need twice the =org-babel-next-src-block= call, and not only
  once in the =should-error= form.

Thanks.

Best regards,
  Seb

-- 
Sebastien Vauban