Accessing properties in org-babel source code blocks

Question

noweb expantion is a very nice tool but it generally allows one to refer to other src-code blocks:

#+NAME: hellomessage
#+BEGIN_SRC emacs-lisp
"hello"
#+END_SRC

#+BEGIN_SRC emacs-lisp :noweb yes 
(message <<hellomessage>>)
#+END_SRC

works perfectly. But it is reasonable to want to do template expansion with properties. I would like something like this to work:

#+PROPERTY: hellomessage hello

#+BEGIN_SRC emacs-lisp :noweb yes 
(message "<<hellomessage>>")
#+END_SRC

or

* Example
  :PROPERTIES:
  :hellomessage: hello
  :END:

#+BEGIN_SRC emacs-lisp :noweb yes 
(message "<<hellomessage>>")
#+END_SRC

but it doesn't since noweb seems only to expand named source blocks. Is there any way to do this?

I have thought of using header arguments with the var keyword but that seems somewhat artificial since the property then is "specific" to src blocks. I would like to avoid this since I would also want to use the property in the normal org-mode way.

Similarly to what Ixemad suggested I tried doing this

* Example
  :PROPERTIES:
  :hellomessage: hello
  :END:

  #+NAME: get_property
  #+BEGIN_SRC elisp :var prop=""
    (org-entry-get nil prop t)
  #+END_SRC
  #+RESULTS: get_property

  #+BEGIN_SRC emacs-lisp :noweb yes
    (message "<<get_property("hellomessage")>>")
  #+END_SRC

  #+RESULTS:
  : hello1

but the problem is that the org-entry-get gets evaluated where the get_property code block is defined, not where it is called as seen by the following example

* Example1
  :PROPERTIES:
  :hellomessage: hello1
  :END:

  #+NAME: get_property
  #+BEGIN_SRC elisp :var prop=""
    (org-entry-get nil prop t)
  #+END_SRC
  #+RESULTS: get_property

  #+BEGIN_SRC emacs-lisp :noweb yes
    (message "<<get_property("hellomessage")>>")
  #+END_SRC

  #+RESULTS:
  : hello1

* Example2
  :PROPERTIES:
  :hellomessage: hello2
  :END:
  #+BEGIN_SRC emacs-lisp :noweb yes
    (message "<<get_property("hellomessage")>>")
  #+END_SRC

  #+RESULTS:
  : hello1

The second result should have been hello2.

Answer 1

I'm not entirely sure I understand the constraints/requirements you're interested in (e.g. must a solution involve noweb evaluation), but one aspect of this question is similar to a problem I wrestled with recently: block calls and their location. The best solution I could find made use of org-babel-current-src-block-location.

Here are some examples; one uses Elisp only and the other uses noweb block evaluation and org-babel-current-src-block-location. Both appear to solve the block-location problem, if I'm understanding it correctly.

  * Example
    :PROPERTIES:
    :hellomessage: hello
    :END:

    #+NAME: get_property
    #+BEGIN_SRC emacs-lisp :var prop_name="" :results silent
    (org-with-point-at org-babel-current-src-block-location
      (org-entry-get nil prop_name t))
    #+END_SRC

    #+HEADER: :var prop_message=(org-entry-get nil "hellomessage" t)
    #+BEGIN_SRC emacs-lisp
      (message prop_message)
    #+END_SRC

    #+RESULTS:
    : hello

    #+BEGIN_SRC emacs-lisp :noweb yes
      (message "<<get_property("hellomessage")>>")
    #+END_SRC

    #+RESULTS:
    : hello

  * Example2
    :PROPERTIES:
    :hellomessage: hello2
    :END:


    #+HEADER: :var prop_message=(org-entry-get nil "hellomessage" t)
    #+BEGIN_SRC emacs-lisp
      (message prop_message)
    #+END_SRC

    #+RESULTS:
    : hello2

    #+BEGIN_SRC emacs-lisp :noweb yes
      (message "<<get_property("hellomessage")>>")
    #+END_SRC

    #+RESULTS:
    : hello2

Answer 2

From the Noweb reference syntax, you can evaluate code block before expansion.

* Example
  :PROPERTIES:
  :hellomessage: hello
  :END:

  #+NAME: get_property
  #+BEGIN_SRC elisp :var prop=""
    (org-entry-get nil prop t)
  #+END_SRC
  #+RESULTS: get_property

  #+BEGIN_SRC emacs-lisp :noweb
    (message "<<get_property("hellomessage")>>")
  #+END_SRC