From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Charles C. Berry" <ccberry@ucsd.edu>
Subject: Re: [bug][babel] noweb gotcha
Date: Thu, 12 Jun 2014 14:21:14 -0700
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To: Eric Schulte <schulte.eric@gmail.com>
Cc: emacs-orgmode@gnu.org

On Thu, 12 Jun 2014, Eric Schulte wrote:

> Charles Berry <ccberry@ucsd.edu> 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.


HTH,

Chuck