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

[Charles C. Berry]

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.


HTH,

Chuck