[O] Automatically adding local variables to tangled file

[Rainer M Krug]

Hi 

I am trying to improve my workflow of literate programming of R in
org. My org file is tangled into many R files and I am using ESS to
debug.

If an error occurs, I can jump via ESS to the .R file, and in a second
step via calling org-babel-tangle-jump-to-org into the org file where
the buggy line sits.


Now this is error prone, as one (or is it only me?) is easily tempted to
edit the R file which is reverted after the next tangle.

So I was thinking: what about calling org-babel-tangle-jump-to-org
directly from ESS. Vitalie Spinu looked into this option, and came up with the
following suggestion:

If the tangled .R file contains a local variable, one could easily
identify that it is a tangled file and call org-babel-tangle-jump-to-org
and would be at the line causing the error.

Therefore my question:

Would it be possible and reasonable, to add a local variable to each
tangled file which identifies the file as an file tangled from an org
mode file?

He added the following to his config file to test the approach:

,----
|  (defvar org-babel-tangled-file nil
|      "If non-nill, current file was tangled with org-babel-tangle")
|    (put 'org-babel-tangled-file 'safe-local-variable 'booleanp)
|    
|    (defun org-babel-mark-file-as-tangled ()
|      (add-file-local-variable 'org-babel-tangled-file t)
|      (basic-save-buffer))
| 
|    (add-hook 'org-babel-post-tangle-hook 'org-babel-mark-file-as-tangled)
`----

and he also already added automatic redirection to the org mode file via
org-babel-tangle-jump-to-org to ESS on SVN.

To keep backwards compatibility, a variable
org-babel-tangle-add-tangled-file-variable could be introduced, which
can have the following values:

- nil :: (default) do not add anything
- t :: org-babel-tangled-file is added as t to the tangled files
- "name" :: org-babel-tangled-file is set to the org file name
- "path" :: org-babel-tangled-file is set to the path of the org file
- "all" :: org-babel-tangled-file is set to the full name including path
           of the org file

I can even imagine many more possibilities for the use of local file
variables to store meta data in the tangled file (VCS info comes to
mind, which would enable one to even go back to older revisions based on
the tangled code rather easily).

Cheers,

Rainer

-- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation Biology, 
UCT), Dipl. Phys. (Germany)

Centre of Excellence for Invasion Biology
Stellenbosch University
South Africa

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