scc_info: fix split_on_sets

* spot/twaalgos/sccinfo.cc (split_on_sets): Correctly register APs.
* tests/python/sccsplit.py: New file.
* tests/Makefile.am: Add it.
* NEWS: Mention the bug.

NEWS

@@ -34,6 +34,11 @@ New in spot 2.6.0.dev  (not yet released)
   - "ltlfilt --suspendable" is now a synonym for
     "ltlfilt --universal --eventual".
 
+  Bugs fixed:
+
+  - scc_info::split_on_sets() did not correctly register the
+    atomic propositions of the returned automata.
+
 New in spot 2.6  (2018-07-04)
 
   Command-line tools:

spot/twaalgos/sccinfo.cc

@@ -528,6 +528,7 @@ namespace spot
         cur.assign(aut_->num_states(), false);
 
         auto copy = make_twa_graph(aut_->get_dict());
+        copy->copy_ap_of(aut_);
         copy->copy_acceptance_of(aut_);
         copy->prop_state_acc(aut_->prop_state_acc());
         transform_accessible(aut_, copy, [&](unsigned src,

tests/Makefile.am

@@ -400,6 +400,7 @@ TESTS_python = \
   python/sbacc.py \
   python/sccfilter.py \
   python/sccinfo.py \
+  python/sccsplit.py \
   python/semidet.py \
   python/setacc.py \
   python/setxor.py \

tests/python/sccsplit.py

@@ -0,0 +1,30 @@
+#!/usr/bin/python3
+# -*- mode: python; coding: utf-8 -*-
+# Copyright (C) 2018 Laboratoire de Recherche et Développement de
+# l'EPITA.
+#
+# This file is part of Spot, a model checking library.
+#
+# Spot is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# Spot is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+# License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import spot
+
+aut = spot.translate('GF(a <-> Xa) & GF(b <-> XXb)')
+si = spot.scc_info(aut)
+s = ""
+for aut2 in si.split_on_sets(0, [0]):
+    # This call to to_str() used to fail because split_on_sets had not
+    # registered the atomic propositions of aut
+    s += aut2.to_str();
+assert spot.automaton(s).num_states() == 8