New pp (was: bug#25295: 26.0.50; Represent eieio objects using object-print in backtraces and edebug)

[Stefan Monnier]

> I posted an initial draft at
> https://debbugs.gnu.org/cgi/bugreport.cgi?bug=25122#21, I'm not seeing
> as much speedup as I'd hoped, though I haven't tried optimizing it yet.

Thanks.  I answered there about the performance aspect.

> +(defun pp-prin1 (object &optional stream)
> +  (let ((cl-print-readably nil)
> +        (stream (make-pp-state (or stream standard-output))))
> +    (pp--scan :open-block stream)
> +    (prog1 (cl-prin1 object (cons :pprint stream))
                               ^^^^^^^^^^^^^^^^^^^^^
Why not just pass `stream' since it's a struct and we can hence dispatch
based on its type?

> +;; fallback to standard `cl-print-object'.
> +(cl-defmethod cl-print-object (object (stream (head :pprint)))
> +  (pp--scan (cl-prin1-to-string object) (cdr stream))
> +  object)

Hmm... but if we use such a pseudo-stream here, doesn't it break all
calls to `princ' within other cl-print-object methods (i.e. forcing us
the override pretty much all existing cl-print-object methods with
a pprint-specific one)?


        Stefan