Re: [O] Syntax error warnings? (Especially important with :noweb-ref's)

2012-01-30 Thread Yu 
Hello!

Thanks for the reply. The problem was, that I assumed the list
`org-babel-noweb-error-langs' to require the same form as
`org-babel-load-languages', i.e. something like
  :   ( (latex . t) (python . t) (sh . t) )

I didn't expect it to require a plain list of strings.

Now, that this misunderstanding is cleared though, the next problem
becomes visible: The common workflow I excepted is:
 1. Define an overall structure of the task.
 2. Run org-babel-tangle
 3. If there are no errors: Finished.
Else:
  - Choose the next block to implement from the list of unresolved blocks.
  - Rerun from 1.

In the current implementation, the first unresolved code block stops
at the `error' statement.

Idea


Instead of throwing an error, just a warning should be given. A simple
implementation could be replacing, in ob.el,
`org-babel-expand-noweb-references',

(error %s (concat
(org-babel-noweb-wrap source-name)
could not be resolved (see 
`org-babel-noweb-error-langs')))

by

  (progn
(lwarn 'tangle :warning %s
   (concat (org-babel-noweb-wrap source-name)
could not be resolved (see 
   `org-babel-noweb-error-langs')))
)

(the (progn-wrapping) is needed to ensure the enclosing if statement
returns a string as expected by `split-string').

The solution has the weakness though, that the warning buffer doesn't
show up automatically (due to the save-excursion I assume, so probably
the warnings should be thrown in one go /after/ the save excursion and
be collected into a list until then. (Multiple advantages:
`add-to-list' can take care of multipli occuring warnings and a single
warning is more clear by far then several warnings).

king regards, Yu


2012/1/30 Eric Schulte eric.schu...@gmx.com:
 Yu yu_...@gmx.at writes:

 I tried my test file just again with a fresh pull from git:

 :  `cat  file1  file2'
 now expands as expected, but otherwise I don't see a change. Because I
 thought, well, maybe it's language specific, I made a new example.

 == test.org ==
 #+begin_src emacs-lisp :tangle test.out :noweb tangle
   (progn
     task1
     task2
     (setq  1  2)
     (setq symbol 1)
   )
 #+end_src
 #+begin_src emacs-lisp :noweb-ref task1 :noweb tangle
   (princ Hallo Welt!\n)
 #+end_src
 

 exports to
 == test.out ==

 (progn
   (princ Hallo Welt!\n)

   (setq  1  2)
   (setq  1)
 )
 ==

 still without any error message.


 When I add emacs-lisp to the `org-babel-noweb-error-langs' variable then
 errors are raised for both task2 and symbol.

 #+BEGIN_SRC emacs-lisp
  (add-to-list 'org-babel-noweb-error-langs emacs-lisp)
 #+END_SRC


 As for the (here pretty artificial) case of symbol, I suppose
 avoiding that problem would require being able to suppress the special
 meaning of the construct, which would render the source less readable,
 so I guess one will just want to avoid this clash (e.g. inserting the
 spaces in shell scripts before/after the filename in a cmd  EOF 
 target construct, so here your solution is certainly sufficient for
 all but very exotic cases :-)


 Also, see the recent emails on list in which the ability to set custom
 alternatives for  and  we added.  The example used in the email was
 the utf8 symbols « and » which should not occur in code.

 Best,


  Suggestion 
 For cases, where a corresponding code block is not found: It would
 probably help in debugging and prevent compilers/interpreters from
 ignoring the missing code, if instead of an empty string, the
 foo construct itself was inserted, i.e. effectively not expanded
 at all. E.g. my sample code would result in the lisp interpreter
 trying to get the value for an undefined variable task2, which
 would be a quite obvious cause of failure.

 kind regards, Yu


 2012/1/24 Eric Schulte eric.schu...@gmx.com:
 Yu yu_...@gmx.at writes:

 Actually, I set `org-babel-noweb-error-langs' to be the same as
 `org-babel-load-languages' (forgot to mention that). Specifically it
 contains
 By the way, I retested it again today with the latest version from
 git. Still the same result.


 OK, Thanks for your persistence on this.  I've just pushed up a fix for
 two issues.

 1. noweb reference names (e.g., that which is between the s) must
   both start and end with non-whitespace characters

 2. some of my recent changes broke the error reporting behavior
   associated with `org-babel-noweb-error-langs', I've fixed this
   behavior.

 Please do let me know if you continue to experience any problems.

 Best,


 2012/1/23 Eric Schulte eric.schu...@gmx.com:
 Have you tried using the

Re: [O] Syntax error warnings? (Especially important with :noweb-ref's)

2012-01-30 Thread Eric Schulte 
Yu yu_...@gmx.at writes:

 Hello!

 Thanks for the reply. The problem was, that I assumed the list
 `org-babel-noweb-error-langs' to require the same form as
 `org-babel-load-languages', i.e. something like
   :   ( (latex . t) (python . t) (sh . t) )

 I didn't expect it to require a plain list of strings.

 Now, that this misunderstanding is cleared though, the next problem
 becomes visible: The common workflow I excepted is:
  1. Define an overall structure of the task.
  2. Run org-babel-tangle
  3. If there are no errors: Finished.
 Else:
   - Choose the next block to implement from the list of unresolved blocks.
   - Rerun from 1.

 In the current implementation, the first unresolved code block stops
 at the `error' statement.


I would suggest that you stubb out empty code blocks for those blocks
which you want to reference elsewhere but have not yet implemented.
Such blocks could all hold the same indicator string (something like
TODO or FIXME) so that the presence of unimplemented blocks is easy to
find in tangled code.

As you mention below there are complications with a multi-tiered warning
and error system which I believe would make the noweb error system more
confusing and harder to use.


 Idea
 

 Instead of throwing an error, just a warning should be given. A simple
 implementation could be replacing, in ob.el,
 `org-babel-expand-noweb-references',

   (error %s (concat
   (org-babel-noweb-wrap source-name)
   could not be resolved (see 
   `org-babel-noweb-error-langs')))

 by

 (progn
   (lwarn 'tangle :warning %s
  (concat (org-babel-noweb-wrap source-name)
   could not be resolved (see 
  `org-babel-noweb-error-langs')))
   )

 (the (progn-wrapping) is needed to ensure the enclosing if statement
 returns a string as expected by `split-string').

 The solution has the weakness though, that the warning buffer doesn't
 show up automatically (due to the save-excursion I assume, so probably
 the warnings should be thrown in one go /after/ the save excursion and
 be collected into a list until then. (Multiple advantages:
 `add-to-list' can take care of multipli occuring warnings and a single
 warning is more clear by far then several warnings).

 king regards, Yu


 2012/1/30 Eric Schulte eric.schu...@gmx.com:
 Yu yu_...@gmx.at writes:

 I tried my test file just again with a fresh pull from git:

 :  `cat  file1  file2'
 now expands as expected, but otherwise I don't see a change. Because I
 thought, well, maybe it's language specific, I made a new example.

 == test.org ==
 #+begin_src emacs-lisp :tangle test.out :noweb tangle
   (progn
     task1
     task2
     (setq  1  2)
     (setq symbol 1)
   )
 #+end_src
 #+begin_src emacs-lisp :noweb-ref task1 :noweb tangle
   (princ Hallo Welt!\n)
 #+end_src
 

 exports to
 == test.out ==

 (progn
   (princ Hallo Welt!\n)

   (setq  1  2)
   (setq  1)
 )
 ==

 still without any error message.


 When I add emacs-lisp to the `org-babel-noweb-error-langs' variable then
 errors are raised for both task2 and symbol.

 #+BEGIN_SRC emacs-lisp
  (add-to-list 'org-babel-noweb-error-langs emacs-lisp)
 #+END_SRC


 As for the (here pretty artificial) case of symbol, I suppose
 avoiding that problem would require being able to suppress the special
 meaning of the construct, which would render the source less readable,
 so I guess one will just want to avoid this clash (e.g. inserting the
 spaces in shell scripts before/after the filename in a cmd  EOF 
 target construct, so here your solution is certainly sufficient for
 all but very exotic cases :-)


 Also, see the recent emails on list in which the ability to set custom
 alternatives for  and  we added.  The example used in the email was
 the utf8 symbols « and » which should not occur in code.

 Best,


  Suggestion 
 For cases, where a corresponding code block is not found: It would
 probably help in debugging and prevent compilers/interpreters from
 ignoring the missing code, if instead of an empty string, the
 foo construct itself was inserted, i.e. effectively not expanded
 at all. E.g. my sample code would result in the lisp interpreter
 trying to get the value for an undefined variable task2, which
 would be a quite obvious cause of failure.

 kind regards, Yu


 2012/1/24 Eric Schulte eric.schu...@gmx.com:
 Yu yu_...@gmx.at writes:

 Actually, I set `org-babel-noweb-error-langs' to be the same as
 `org-babel-load-languages' (forgot to mention that). Specifically it
 contains
 By the way, I retested it again today with the latest version from
 git.

Re: [O] Syntax error warnings? (Especially important with :noweb-ref's)

2012-01-23 Thread Eric Schulte 
Have you tried using the `org-babel-noweb-error-langs' variable that I
mentioned previously?  It should help in these situations.

Yu yu_...@gmx.at writes:

 Hello again!

 I thought about the *noweb* part again. I tried the following:

 ==
 #+begin_src sh :tangle test.out :noweb tangle
   task1
   cat  test.org  test.out2
 #+end_src
 #+begin_src sh :noweb-ref task1
   echo hello world
 #+end_src
 ==

 The tangled output file test.out looked like this:
 ==
 /bin/sh

 echo hello world
 cat  test.out2
 ==

 i.e. the syntactically valid  test.org  construct was omitted.
 Thus a separate syntax for forcing a literal  in the tangled
 output is needed anyway (if not yet implemented) and if so, warning
 about undefined code blocks should be possible too.

 The big relevance of warning about undefined and never used code
 blocks struck me, when recently I tried to use it again. The natural
 work flow to me would have been to write something like

  : The task at hand has an overall structure
  : #+begin_src python :tangle foo.py :noweb tangle
  :   read the data
  :   generate derived information
  :   output the results
  : #+end_src

 When proceeding after this however I would have to keep in mind open
 tasks or (slightly better) to instantly create TODO sections for said
 blocks. However, having this order of working imposed on me sort of
 defeats the purpose for my understanding. I'd rather prefer to do an
 `M-x org-babel-tangle' tell me, that I forgot to implement one of the
 partial tasks, rather than having to find out missing code blocks from
 the output file (where, as mentioned, they result in nothing rather
 than an unresolved ... construct).

 kind regards, Yu



 2012/1/14 Eric Schulte eric.schu...@gmx.com:
 Yu yu_...@gmx.at writes:

 Hello!

 I was wondering, if there is a way to get warnings for typos (e.g.
 when specifying invalid properties or header arguments). It can just
 easily happen that I mix up e.g. :exports and :export (though
 that's probably a very harmless example).


 While there is currently no way to do this there are two related
 functions which should help.

 ,[org-babel-view-src-block-info] bound to C-c C-v I
 | org-babel-view-src-block-info is an interactive Lisp function in
 | `ob.el'.
 |
 | (org-babel-view-src-block-info)
 |
 | Display information on the current source block.
 | This includes header arguments, language and name, and is largely
 | a window into the `org-babel-get-src-block-info' function.
 `

 and

 ,[org-babel-check-src-block] bound to C-c C-v c
 | org-babel-check-src-block is an interactive Lisp function in `ob.el'.
 |
 | (org-babel-check-src-block)
 |
 | Check for misspelled header arguments in the current code block.
 `

 This problem is not trivial because new language are permitted to create
 and use *any* header arguments they like, so there are no /wrong/ header
 arguments, there are only /suspicious/ header arguments (like the
 :exports option you suggest).  The above function reports any suspicious
 header arguments.  Perhaps there would be a way to integrate the above
 function with flyspell for automatic highlighting of suspicious header
 arguments.  I'll put looking into such integration on my long-term Org
 task queue.


 More important it gets though, when trying to use the literate
 programming facilities.

 Say I have a source code

 #+begin_src sh :noweb tangle :tangle foo.sh
   foo
 #+end_src
 #+begin_src sh :noweb-ref fo
   echo '... how are you?';
 #+end_src

 then tangling would run through without any indication of the typo in
 the name of the foo block. Such errors might be hard to debug,
 because there is no indication of the error, maybe nothing other than
 runtime errors.

 An error message for the /use/ of undefined references only wouldn't
 avoid such problems either, e.g. consider

 #+begin_src sh :noweb tangle :tangle foo.sh
   foo
 #+end_src
 #+begin_src sh :noweb-ref foo
   echo 'Hello World...';
 #+end_src
 #+begin_src sh :noweb-ref fo
   echo 'Hello World...';
 #+end_src

 where the only detectable error is, that fo was never used anywhere.

 A similiar question (though without the second part) was asked here:
 http://lists.gnu.org/archive/html/emacs-orgmode/2009-11/msg00273.html
 As far as I can tell, it stands unanswered.


 Yes, although in many languages constructs like foo are valid code,
 so it would be inappropriate for tangling to raise errors by default.
 It is possible to turn on such errors on a language-by-language basis,
 by customizing the following variable.

 ,[org-babel-noweb-error-langs]
 | org-babel-noweb-error-langs is a variable defined in `ob.el'.
 | Its value is nil
 |
 | Documentation:
 | Languages for which Babel will raise literate programming errors.
 | List of languages for which errors should be raised when the
 | source code block

Re: [O] Syntax error warnings? (Especially important with :noweb-ref's)

2012-01-23 Thread Eric Schulte 
Fixed. Thanks,

Sebastien Vauban wxhgmqzgw...@spammotel.com writes:

 Hi Eric,

 Eric Schulte wrote:
 there are two related functions which should help.

 ,[org-babel-view-src-block-info] bound to C-c C-v I
 | org-babel-view-src-block-info is an interactive Lisp function in
 | `ob.el'.
 | 
 | (org-babel-view-src-block-info)
 | 
 | Display information on the current source block.
 | This includes header arguments, language and name, and is largely
 | a window into the `org-babel-get-src-block-info' function.
 `

 and

 ,[org-babel-check-src-block] bound to C-c C-v c
 | org-babel-check-src-block is an interactive Lisp function in `ob.el'.
 | 
 | (org-babel-check-src-block)
 | 
 | Check for misspelled header arguments in the current code block.
 `

 When checking for suspicious header arguments on[1]:

 #+name: mean
 #+begin_src emacs-lisp :var lst=()
   (let ((num (car lst)) (nums (cdr lst)))
 (/ (float (+ num (apply #'+ nums))) (1+ (length nums
 #+end_src

 it reports:

 supplied header var is suspiciously close to dir

 Can you enlighten me on what's suspicious here?

 Best regards,
   Seb

 Footnotes:

 [1] which is supposed to be used in the following table:

 |   1 |
 |   2 |
 |   3 |
 |   4 |
 |   5 |
 |   6 |
 | 3.5 |
 #+TBLFM: @7$1='(sbe mean (lst @1..@6))

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

Re: [O] Syntax error warnings? (Especially important with :noweb-ref's)

2012-01-22 Thread Sebastien Vauban 
Hi Eric,

Eric Schulte wrote:
 there are two related functions which should help.

 ,[org-babel-view-src-block-info] bound to C-c C-v I
 | org-babel-view-src-block-info is an interactive Lisp function in
 | `ob.el'.
 | 
 | (org-babel-view-src-block-info)
 | 
 | Display information on the current source block.
 | This includes header arguments, language and name, and is largely
 | a window into the `org-babel-get-src-block-info' function.
 `

 and

 ,[org-babel-check-src-block] bound to C-c C-v c
 | org-babel-check-src-block is an interactive Lisp function in `ob.el'.
 | 
 | (org-babel-check-src-block)
 | 
 | Check for misspelled header arguments in the current code block.
 `

When checking for suspicious header arguments on[1]:

#+name: mean
#+begin_src emacs-lisp :var lst=()
  (let ((num (car lst)) (nums (cdr lst)))
(/ (float (+ num (apply #'+ nums))) (1+ (length nums
#+end_src

it reports:

supplied header var is suspiciously close to dir

Can you enlighten me on what's suspicious here?

Best regards,
  Seb

Footnotes:

[1] which is supposed to be used in the following table:

|   1 |
|   2 |
|   3 |
|   4 |
|   5 |
|   6 |
| 3.5 |
#+TBLFM: @7$1='(sbe mean (lst @1..@6))

-- 
Sebastien Vauban

Re: [O] Syntax error warnings? (Especially important with :noweb-ref's)

2012-01-21 Thread Yu 
Hello again!

I thought about the *noweb* part again. I tried the following:

==
#+begin_src sh :tangle test.out :noweb tangle
  task1
  cat  test.org  test.out2
#+end_src

#+begin_src sh :noweb-ref task1
  echo hello world
#+end_src
==

The tangled output file test.out looked like this:
==
/bin/sh

echo hello world
cat  test.out2
==

i.e. the syntactically valid  test.org  construct was omitted.
Thus a separate syntax for forcing a literal  in the tangled
output is needed anyway (if not yet implemented) and if so, warning
about undefined code blocks should be possible too.

The big relevance of warning about undefined and never used code
blocks struck me, when recently I tried to use it again. The natural
work flow to me would have been to write something like

 : The task at hand has an overall structure
 : #+begin_src python :tangle foo.py :noweb tangle
 :   read the data
 :   generate derived information
 :   output the results
 : #+end_src

When proceeding after this however I would have to keep in mind open
tasks or (slightly better) to instantly create TODO sections for said
blocks. However, having this order of working imposed on me sort of
defeats the purpose for my understanding. I'd rather prefer to do an
`M-x org-babel-tangle' tell me, that I forgot to implement one of the
partial tasks, rather than having to find out missing code blocks from
the output file (where, as mentioned, they result in nothing rather
than an unresolved ... construct).

kind regards, Yu



2012/1/14 Eric Schulte eric.schu...@gmx.com:
 Yu yu_...@gmx.at writes:

 Hello!

 I was wondering, if there is a way to get warnings for typos (e.g.
 when specifying invalid properties or header arguments). It can just
 easily happen that I mix up e.g. :exports and :export (though
 that's probably a very harmless example).


 While there is currently no way to do this there are two related
 functions which should help.

 ,[org-babel-view-src-block-info] bound to C-c C-v I
 | org-babel-view-src-block-info is an interactive Lisp function in
 | `ob.el'.
 |
 | (org-babel-view-src-block-info)
 |
 | Display information on the current source block.
 | This includes header arguments, language and name, and is largely
 | a window into the `org-babel-get-src-block-info' function.
 `

 and

 ,[org-babel-check-src-block] bound to C-c C-v c
 | org-babel-check-src-block is an interactive Lisp function in `ob.el'.
 |
 | (org-babel-check-src-block)
 |
 | Check for misspelled header arguments in the current code block.
 `

 This problem is not trivial because new language are permitted to create
 and use *any* header arguments they like, so there are no /wrong/ header
 arguments, there are only /suspicious/ header arguments (like the
 :exports option you suggest).  The above function reports any suspicious
 header arguments.  Perhaps there would be a way to integrate the above
 function with flyspell for automatic highlighting of suspicious header
 arguments.  I'll put looking into such integration on my long-term Org
 task queue.


 More important it gets though, when trying to use the literate
 programming facilities.

 Say I have a source code

 #+begin_src sh :noweb tangle :tangle foo.sh
   foo
 #+end_src
 #+begin_src sh :noweb-ref fo
   echo '... how are you?';
 #+end_src

 then tangling would run through without any indication of the typo in
 the name of the foo block. Such errors might be hard to debug,
 because there is no indication of the error, maybe nothing other than
 runtime errors.

 An error message for the /use/ of undefined references only wouldn't
 avoid such problems either, e.g. consider

 #+begin_src sh :noweb tangle :tangle foo.sh
   foo
 #+end_src
 #+begin_src sh :noweb-ref foo
   echo 'Hello World...';
 #+end_src
 #+begin_src sh :noweb-ref fo
   echo 'Hello World...';
 #+end_src

 where the only detectable error is, that fo was never used anywhere.

 A similiar question (though without the second part) was asked here:
 http://lists.gnu.org/archive/html/emacs-orgmode/2009-11/msg00273.html
 As far as I can tell, it stands unanswered.


 Yes, although in many languages constructs like foo are valid code,
 so it would be inappropriate for tangling to raise errors by default.
 It is possible to turn on such errors on a language-by-language basis,
 by customizing the following variable.

 ,[org-babel-noweb-error-langs]
 | org-babel-noweb-error-langs is a variable defined in `ob.el'.
 | Its value is nil
 |
 | Documentation:
 | Languages for which Babel will raise literate programming errors.
 | List of languages for which errors should be raised when the
 | source code block satisfying a noweb reference in this language
 | can not be resolved.
 `


 On a side note: What is the customary way to mention the
 noweb-relevant name of a source block in the html/pdf export?

Re: [O] Syntax error warnings? (Especially important with :noweb-ref's)

2012-01-14 Thread Eric Schulte 
Yu yu_...@gmx.at writes:

 Hello!

 I was wondering, if there is a way to get warnings for typos (e.g.
 when specifying invalid properties or header arguments). It can just
 easily happen that I mix up e.g. :exports and :export (though
 that's probably a very harmless example).


While there is currently no way to do this there are two related
functions which should help.

,[org-babel-view-src-block-info] bound to C-c C-v I
| org-babel-view-src-block-info is an interactive Lisp function in
| `ob.el'.
| 
| (org-babel-view-src-block-info)
| 
| Display information on the current source block.
| This includes header arguments, language and name, and is largely
| a window into the `org-babel-get-src-block-info' function.
`

and

,[org-babel-check-src-block] bound to C-c C-v c
| org-babel-check-src-block is an interactive Lisp function in `ob.el'.
| 
| (org-babel-check-src-block)
| 
| Check for misspelled header arguments in the current code block.
`

This problem is not trivial because new language are permitted to create
and use *any* header arguments they like, so there are no /wrong/ header
arguments, there are only /suspicious/ header arguments (like the
:exports option you suggest).  The above function reports any suspicious
header arguments.  Perhaps there would be a way to integrate the above
function with flyspell for automatic highlighting of suspicious header
arguments.  I'll put looking into such integration on my long-term Org
task queue.


 More important it gets though, when trying to use the literate
 programming facilities.

 Say I have a source code

 #+begin_src sh :noweb tangle :tangle foo.sh
   foo
 #+end_src
 #+begin_src sh :noweb-ref fo
   echo '... how are you?';
 #+end_src

 then tangling would run through without any indication of the typo in
 the name of the foo block. Such errors might be hard to debug,
 because there is no indication of the error, maybe nothing other than
 runtime errors.

 An error message for the /use/ of undefined references only wouldn't
 avoid such problems either, e.g. consider

 #+begin_src sh :noweb tangle :tangle foo.sh
   foo
 #+end_src
 #+begin_src sh :noweb-ref foo
   echo 'Hello World...';
 #+end_src
 #+begin_src sh :noweb-ref fo
   echo 'Hello World...';
 #+end_src

 where the only detectable error is, that fo was never used anywhere.

 A similiar question (though without the second part) was asked here:
 http://lists.gnu.org/archive/html/emacs-orgmode/2009-11/msg00273.html
 As far as I can tell, it stands unanswered.


Yes, although in many languages constructs like foo are valid code,
so it would be inappropriate for tangling to raise errors by default.
It is possible to turn on such errors on a language-by-language basis,
by customizing the following variable.

,[org-babel-noweb-error-langs]
| org-babel-noweb-error-langs is a variable defined in `ob.el'.
| Its value is nil
| 
| Documentation:
| Languages for which Babel will raise literate programming errors.
| List of languages for which errors should be raised when the
| source code block satisfying a noweb reference in this language
| can not be resolved.
`


 On a side note: What is the customary way to mention the
 noweb-relevant name of a source block in the html/pdf export? After
 all, if a code-block states
 : task1
 : task2
 the reader needs to know, which code blocks define these.


Currently there is no automated support for this, so you should simply
name code blocks manually, however this topic has been raised recently
in another thread and there does seem to be interest for automated
support.

Best,



 kind regards, Yu


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

[O] Syntax error warnings? (Especially important with :noweb-ref's)

2012-01-12 Thread Yu 
Hello!

I was wondering, if there is a way to get warnings for typos (e.g.
when specifying invalid properties or header arguments). It can just
easily happen that I mix up e.g. :exports and :export (though
that's probably a very harmless example).

More important it gets though, when trying to use the literate
programming facilities.

Say I have a source code

#+begin_src sh :noweb tangle :tangle foo.sh
  foo
#+end_src
#+begin_src sh :noweb-ref fo
  echo '... how are you?';
#+end_src

then tangling would run through without any indication of the typo in
the name of the foo block. Such errors might be hard to debug,
because there is no indication of the error, maybe nothing other than
runtime errors.

An error message for the /use/ of undefined references only wouldn't
avoid such problems either, e.g. consider

#+begin_src sh :noweb tangle :tangle foo.sh
  foo
#+end_src
#+begin_src sh :noweb-ref foo
  echo 'Hello World...';
#+end_src
#+begin_src sh :noweb-ref fo
  echo 'Hello World...';
#+end_src

where the only detectable error is, that fo was never used anywhere.

A similiar question (though without the second part) was asked here:
http://lists.gnu.org/archive/html/emacs-orgmode/2009-11/msg00273.html
As far as I can tell, it stands unanswered.

On a side note: What is the customary way to mention the
noweb-relevant name of a source block in the html/pdf export? After
all, if a code-block states
: task1
: task2
the reader needs to know, which code blocks define these.


kind regards, Yu