Issue when pickling a formal function

[sagetrac-cdsousa]

There is a problem in symbolic function pickling:

sage: x = var('x'); f = function('f',x) ; s = dumps(f) ; loads(s)
RuntimeError: unknown function 'f' in archive

The error was not present in Sage 4.7 but it is in newer versions.
It was suggested (http://groups.google.com/group/sage-support/browse_thread/thread/b439844f2fa0b675) that it is related to Pynac.
Pynac was updated to 0.2.2 (sage-4.7.1.alpha1) and then to 0.2.3
(sage-4.7.1.alpha4) according to sage 4.7.1 changelog.

CC: @jpflori @burcin @jasongrout @sagetrac-dsm @orlitzky

Component: symbolics

Keywords: pynac

Author: Michael Orlitzky

Reviewer: Nils Bruin, Burcin Erocal

Merged: sage-5.1.beta1

Issue created by migration from https://trac.sagemath.org/ticket/11919

[kcrisman]

Description changed:

--- 
+++ 
@@ -8,4 +8,4 @@
 The error was not present in Sage 4.7 but it is in newer versions.
 It was suggested (http://groups.google.com/group/sage-support/browse_thread/thread/b439844f2fa0b675) that it is related to Pynac.
 Pynac was updated to 0.2.2 (sage-4.7.1.alpha1) and then to 0.2.3 
-(sage-4.7.1.alpha4) according to sage 7.4.1 changelog.
+(sage-4.7.1.alpha4) according to sage 4.7.1 changelog.

[nbruin]

Changed keywords from none to pynac

[orlitzky]

comment:5

I hit this independently using deepcopy(). In sage-4.7:

sage: f = function('f',x)
sage: deepcopy(f)
f(x)

and in 4.8.alpha5:

sage: f = function('f',x)
sage: deepcopy(f)
...
RuntimeError: unknown function 'f' in archive

[orlitzky]

comment:6

Interestingly, if I take the pynac spkg from 4.7 and install it on 5.0.beta7, it doesn't fix the crash.

[orlitzky]

comment:7

I built a copy of 4.7.1, and the crash does happen. So the change was introduced between 4.7 and 4.7.1.

[orlitzky]

comment:8

Okay, this broke with #9240. I can fix it with a one-line change in 4.7.1.alpha4:

diff --git a/sage/symbolic/function.pyx b/sage/symbolic/function.pyx
--- a/sage/symbolic/function.pyx
+++ b/sage/symbolic/function.pyx
@@ -127,6 +127,7 @@
     cdef _register_function(self):
         cdef GFunctionOpt opt
         opt = g_function_options_args(self._name, self._nargs)
+        opt.set_python_func()

         if hasattr(self, '_eval_'):
             opt.eval_func(self)

But there's no longer a set_python_func() method on GFunctionOpt, so I don't know how to fix it in 5.0.beta7. The adventure continues...

[orlitzky]

comment:9

Replying to @orlitzky:

But there's no longer a set_python_func() method on GFunctionOpt, so I don't know how to fix it in 5.0.beta7. The adventure continues...

Disregard that, I'm a moron. Testing a patch now.