Re: [O] [bug][babel] noweb gotcha

[Eric Schulte]

"Charles C. Berry" <address@hidden> writes:

> On Thu, 12 Jun 2014, Eric Schulte wrote:
>
>> Charles Berry <address@hidden> writes:
>>
>>> The following
>>>
>>> ,----
>>> | #+PROPERTY: tangle yes
>>> |
>>> | #+NAME: print-abc
>>> | #+BEGIN_SRC emacs-lisp
>>> | (format
>>> | "<<%s>>" "abc")
>>> | #+END_SRC
>>> |
>>> | #+NAME: print-def
>>> | #+BEGIN_SRC emacs-lisp
>>> | (concat
>>> | "<<" "def" ">>")
>>> | #+END_SRC
>>> |
>>> | #+BEGIN_SRC emacs-lisp :noweb yes
>>> | <<print-abc>>
>>> | <<print-def>>
>>> | #+END_SRC
>>> `----
>>>
>>>
>>>
>>> tangles as
>>>
>>> ,----
>>> | (format
>>> | "<<%s>>" "abc")
>>> |
>>> | (concat
>>> | "<<" "def" ">>")
>>> |
>>> | (format
>>> | "<<%s>>" "abc")
>>> | (concat
>>> | "")
>>> `----
>>>
>>>
>>> Note that ""<<" "def" ">>" disappeared from (concat ...).
>>>
>>> FWIW, adding quotes inside the constant string in org-babel-noweb-wrap:
>>>
>>>
>>> "\\([^ \"\t\n][^\"]+?[^ \"\t]\\|[^ \"\t\n]\\)"
>>>
>>> fixes this instance.
>>>
>>
>> Does this raise any error, or fail silently?
>>
>> Thanks,
>> Eric
>
>
> Alas, it fails silently -- producing the erroneous output.
>
> I guess the issue is that
>
>       `(re-search-forward (org-babel-noweb-wrap) nil t)'
>
> finds quoted expressions like
>
> 1. "<<abc>>"
> 2. (concat "<<" abc ">>")
>
> FWIW,
>
> (re-search-forward
>  (org-babel-noweb-wrap
>   "\\([^ \"\t\n][^\"]+?[^ \"\t]\\|[^ \"\t\n]\\)"
>   ) nil t)
>
> (adding quotes to the [^...] bits) takes care of example 2. Not sure
> if example 1 is a feature or a bug - I sometimes use things like
>
>       "<<text-I-want>>"
>
> so maybe modifying the regex is good enough?
>
> OTOH, <<no-such-chunk>> has no effect. Maybe checking that the
> reference actually resolves is better than tweaking the regexes.
>

So it is currently possible to raise errors when noweb references don't
resolve through the use of the `org-babel-noweb-error-all-langs'
variable.  I just added `org-babel-noweb-error-all-langs' which may be
set to raise such errors regardless of the language of the code block.

Best,
Eric

>
>
> HTH,
>
> Chuck
>
>

-- 
Eric Schulte
https://cs.unm.edu/~eschulte
PGP: 0x614CA05D (see https://u.fsf.org/yw)