Re: using previous =#+results= when =:eval never=

[Berry, Charles]

> On Jul 3, 2021, at 9:35 AM, Greg Minshall <minshall@umich.edu> wrote:
> 
> hi.
> 
> i am trying to simplify adding regression test cases to a program.
> 
> to generate the base, "compared-to" results, i want to write some code
> in a source block, then evaluate it, producing the "true" value.
> 
> then, later during development, i want to check if the code that ran in
> that block gives the same results.  to do this, i preface the test check
> block with, e.g., =:var fu=bar=.  obviously, i do *not* want to
> re-create the base results; so, after producing the base case results, i
> tried marking the source block that produces the results =:eval never=.
> 
> but, doing that, using `:var fu=bar` on a test check source block, fu's
> value is nil. (*)
> 
> is there a way to convince org-mode to, in the face of =:eval never=, go
> ahead and pass the *previous* results?  or, some other idea of how to do
> this?  there will be a large number of these test cases.
> 
> cheers, Greg


Greg,

I think it would be easier to leave :eval alone and instead evaluate the src 
block using `org-babel-ref-resolve' and compare to the current value. Something 
like this is a start:


#+begin_src emacs-lisp
  (defun org-babel-read-named-result (blkname)
    (save-excursion
      (org-babel-goto-named-result blkname)
      (org-babel-read-result)))
#+end_src


#+begin_src emacs-lisp
    (defun compare-old-to-new (refname)
      (let ((new (org-babel-ref-resolve refname))
            (old (org-babel-read-named-result refname)))
        (or (equal old new)
            (format "Comparison failed for block %s" refname))))
#+end_src

Then eval'ing `(compare-old-to-new "testcountsdecompose")` for the ECM you gave 
will give `t` if the result is the same and return a string saying which block 
failed the test.

I suppose you could loop thru `(org-babel-src-block-names)` if you want to 
check all the named blocks in a file.

HTH,

Chuck


> 
> (*) this is sort of confusing, so here's an example:
> 
> #+begin_src org
>  ,#+name: testcountsdecompose
>  ,#+begin_src R :eval never
>    mtcars[1:3,]
>  ,#+end_src
> 
>  ,#+RESULTS: testcountsdecompose
>  |   21 | 6 | 160 | 110 |  3.9 |  2.62 | 16.46 | 0 | 1 | 4 | 4 |
>  |   21 | 6 | 160 | 110 |  3.9 | 2.875 | 17.02 | 0 | 1 | 4 | 4 |
>  | 22.8 | 4 | 108 |  93 | 3.85 |  2.32 | 18.61 | 1 | 1 | 4 | 1 |
> 
>  ,#+name: testcounts
>  ,#+header: :var testcountsdecompose=testcountsdecompose :results output
>  ,#+begin_src R
>    str(testcountsdecompose)
>  ,#+end_src
> 
>  ,#+RESULTS: testcounts
>  :  chr "nil"
> #+end_src
> 
> whereas, if the =testcountsdecompose= source block does *not* have
> =:eval never=, my =testcountsdecompse= variable has all the rows and
> columns i was hoping for.
> 
>