Re: [BUG] Noweb reference eval syntax does not work

[Rasmus <rasmus@gmx.us>]

Hi,

Nicolas Goaziou <mail@nicolasgoaziou.fr> writes:

> fm4d <m@fm4d.net> writes:
>
>> The noweb reference syntax that should insert results of
>> evaluation of src block itself instead of src block as
>> described in `org-babel-expand-noweb-reference` does not
>> seems to work.
>>
>>
>> Code for replication:
>>
>> * Assign 
>>
>> First we assign abc:
>>
>> #+begin_src python :noweb-ref assign_abc
>> abc = "abc" + "def"
>> #+end_src
>>
>> * Use
>>
>> Then we use it in a function:
>>
>> #+begin_src python :noweb tangle :tangle noweb-test.py
>> def x():
>>   <<assign_abc>>
>>   return abc
>>
>> print(x())
>> #+end_src
>>
>>
>> <<assign_abc>> does work, <assign_abc()> fails with this error:
>>
>> (error "Reference ‘assign_abc’ not found in this buffer")
>>   signal(error ("Reference ‘assign_abc’ not found in this buffer"))
>>   error("Reference `%s' not found in this buffer" "assign_abc")
>>   org-babel-ref-resolve("assign_abc()")
>>   ...
>>
>>
>> I am not sure if this is a bug or I am doing something wrong,
>> the documentation on this feature is not very comprehensive.
>
> I just discovered the :noweb-ref parameter.

I have used :noweb yes in the past, but it seems :noweb-ref can be
replaced by name in at least the single blog case:

    #+name: data
    #+BEGIN_SRC R
      set.seed(42)
      df1 <- data.frame(x=rnorm(10), y=rnorm(10))
    #+END_SRC

    #+BEGIN_SRC R :noweb yes
    <<data>>
    colMeans(df1)
    #+END_SRC

As you mention, we’d loose the ability to chain together multiple blocks.
I reckon they are meaningfully the same language, so I don’t see a loss.
The example shown in the manual also does not convince me of the
usefullness of this.

> It is redundant with #+NAME: keyword and slightly broken. Also it
> induces hacks like `org-babel-use-quick-and-dirty-noweb-expansion' to
> work-around its shortcomings. 
>
> Besides, it doesn't make much sense to add the same parameters to
> a bunch of blocks, so I find the syntax dubious.
>
> I understand it can be a handy shortcut for inserting multiple blocks,
> but, all in all, I tend to think it would be simpler to just remove the
> feature, along with `:noweb-sep' and
> `org-babel-use-quick-and-dirty-noweb-expansion'.

I’m happy to kill it off in Org-9.  I don’t know how widely the chaining
of blocks is used, though, and whether the fix is always as simple as
uniting the blocks.

> What do you, and others, think? Is NAME enough for noweb syntax, or is
> there a real need fo :noweb-ref?

I've put Aaron in carbon copy as he’s quite familiar with ob.

Rasmus

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