bug#51037: [PATCH] Make `print-level` & `print-length` customizable in ERT batch tests

[Michael]

Filipp Gunbin <fgunbin@fastmail.fm> writes:

> On 20/11/2021 08:49 -0800, Michael wrote:
>
> > > On 19/11/2021 07:24 -0800, Michael wrote:
> > >
> > > > Lars Ingebrigtsen <larsi@gnus.org> writes:
> > > >
> > > > > Filipp Gunbin <fgunbin@fastmail.fm> writes:
> > > > >
> > > > > > The docstring for backtrace-line-length says: "If set to 
> > > > > > nil
> > > > > > or
> > > > > > zero,
> > > > > > backtrace mode will not abbreviate the forms it prints." 
> > > > > > So
> > > > > > the
> > > > > > above
> > > > > > sentence, which I removed, was indeed not true?  (a quick
> > > > > > look over
> > > > > > its usages confirmed that to me, but I'd like someone else 
> > > > > > to
> > > > > > check)
> > > > >
> > > > > I think the intention is that a nil value of
> > > > > backtrace-line-length
> > > > > shouldn't limit the lengths -- but I haven't tested it.
> > > > > Doesn't it
> > > > > work?
> > > >
> > > > Yes, I'm a bit lost, Filipp... what is your concern? And I
> > > > thought I *had* tested that.
> > >
> > > That the docstring contained a sentence which is not true.  A
> > > minor
> > > issue, of course.  I give examples here:
> > > https://debbugs.gnu.org/cgi/bugreport.cgi?bug=51037#117
> > >
> > > (there was also fix of interactive spec of
> > > `ert-run-tests-interactively',
> > > but that's obvious I think)
> > Hey Filipp,
> >
> > Note that _is_ true, as far as I know, and was intended to be
> > true before my patch, and I verified that it became true with 
> > my
> > patch :) Can you provide a test case that demonstrates it to be
> > not true?
>
> Yes, here 
> https://debbugs.gnu.org/cgi/bugreport.cgi?bug=51037#117, as I
> wrote above..

Oh.... oh, my-- you are on to something here, Filipp. My
apologies for not seeing it sooner. The problem lies in:

   (defun cl-print-to-string-with-limit (print-function value 
   limit)
     ...
     (setq limit (and (natnump limit)
                      (not (zerop limit))
                      limit))
     ;; Since this is used by the debugger when stack space may 
     be
     ;; limited, if you increase print-level here, add more depth 
     in
     ;; call_debugger (bug#31919).
     (let* ((print-length (when limit (min limit 50)))
            (print-level (when limit (min 8 (truncate (log 
            limit)))))


backtrace uses this function to print each frame, and as you can
see, if called with `limit' set to nil, `print-le{vel,ength}`
will *not* keep their current values, they will *also* be set to
`nil`.

So, we could do either of:

   1. As Filipp suggests, just change the contract for
   `ert-batch-backtrace-line-length' to: if set to nil, you get
   full stack traces, period.

   2. change `cl-print-to-string-with-limit' to respect the
   existing values of `print-length' & `print-level' when
   `limit' is nil. Note that the only caller (in Emacs) of this
   function is the backtrace package.

I vote for option 2. What say you all?

--
Michael <sp1ff@pobox.com>