[Octave-patch-tracker] [patch #9980] JSON encoder and decoder, alternative to object2json

[Philip Nienhuis]

Follow-up Comment #9, patch #9980 (project octave):

Thanks for the new patches.


Where in comment #2 I wrote that in Octave-7.0.0 these functions will become
obsolete, if they are in the io package they should still run w/o issues for a
few years until usage of then older Octave Out There is low enough. I think
that is not unreasonable.

I checked and tested a few thing and I see the following in Octave-7.0.0:

>> test toJSON
***** test  ##  PREC input arg test
  assert(toJSON(pi,  0),'3')
  assert(toJSON(pi,  5),'3.1416')
  assert(toJSON(pi, -5),'3.1416')
  assert(toJSON(pi, 25),'3.141592653589793115997963')
  assert(toJSON(pi,  :),'3.14159265358979')
  assert(toJSON(pi, []),'3.14159265358979')
  assert(toJSON(pi, false),'3.14159265358979');  ## this is provoking stmt
  assert(toJSON(pi, {}),'3.14159265358979');          ## issue warning here
!!!!! test failed
invalid empty index expression


due to this statement on L.72:

    [PREC,COMPACT] = {[],PREC}{};


which (as we have discussed) is difficult to disentangle.
As of Octave-7.0.0 empty indexing e.g., var{}, is no longer allowed, see
https://savannah.gnu.org/bugs/?56167.
Replacing by

%    [PREC,COMPACT] = {[],PREC}{};
    PREC = [];
    COMPACT = PREC(:);

makes it work but I don't know if that's the right fix.
The next test, 'toJSON(false)' fails elsewhere (L.234) and
toJSON(reshape(1:8,2,2,2)) fails in L.217. Trying to fix those (just entering
":" between curly brackets) gave 

"error: '_num2str_' undefined near line 170, column 170"


(I know it's defined on L.86) and then I gave up.
Please fix these issues.

Then,

>> test fromJSON
***** test  ## number
 assert(fromJSON('4'),4)
!!!!! test failed
invalid use of 'end': may only be used to index existing value
>> fromJSON('4')
error: invalid use of 'end': may only be used to index existing value
error: called from
    fromJSON>_fromjson_ at line 70 column 25
    fromJSON at line 62 column 9


(perhaps also an Octave-7.0.0 issue)
variable 'obj' needs to be initialized (empty) before it can be indexed with
(end+1).

Also in fromJSON I saw several empty var{} indexing which will error out.

Can you build Octave-7.0.0 to try yourself?
If you're on Linux it shouldn't be too hard, if on Windows I could cross-build
a recent tip for you and upload it somewhere.

I'm on the verge of making a (bug fix) io-2.6.3 release, I really hope you can
delivr toJSON and fromJSON also running in Octave-7+ so that I can include
them in the io package. In fact that's all the release is waiting for.
I hope you can fix all of these issues


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