fix merging of initial states in state-based automata

Fixes #522 reported by Raven Beutner.

* spot/parseaut/parseaut.yy: Make sure all edges leaving
the initial state have the same color.
* THANKS: Add Raven.
* NEWS: Mention the bug.
* tests/core/522.test: New file.
* tests/Makefile.am: Add it.

NEWS

@@ -4,6 +4,12 @@ New in spot 2.11.3.dev  (not yet released)
 
   - spot.acd() no longer depends on jQuery for interactivity.
 
+  Bug fixes:
+
+  - When merging initial states from state-based automata with
+    multiple initial states (because Spot supports only one), the HOA
+    parser could break state-based acceptance.  (Issue #522.)
+
 New in spot 2.11.3  (2022-12-09)
 
   Bug fixes:

THANKS

@@ -48,6 +48,7 @@ Nikos Gorogiannis
 Ondřej Lengál
 Paul Guénézan
 Pierre Ganty
+Raven Beutner
 Reuben Rowe
 Roei Nahum
 Rüdiger Ehlers

spot/parseaut/parseaut.yy

@@ -1,5 +1,5 @@
 /* -*- coding: utf-8 -*-
-** Copyright (C) 2014-2022 Laboratoire de Recherche et Développement
+** Copyright (C) 2014-2023 Laboratoire de Recherche et Développement
 ** de l'Epita (LRDE).
 **
 ** This file is part of Spot, a model checking library.
@@ -2610,7 +2610,7 @@ static void fix_initial_state(result_& r)
   start.resize(std::distance(start.begin(), res));
 
   assert(start.size() >= 1);
-    if (start.size() == 1)
+  if (start.size() == 1)
     {
       if (r.opts.want_kripke)
 	r.h->ks->set_init_state(start.front().front());
@@ -2627,13 +2627,13 @@ static void fix_initial_state(result_& r)
 				    "a single initial state");
 	  return;
 	}
+      auto& aut = r.h->aut;
       // Fiddling with initial state may turn an incomplete automaton
       // into a complete one.
-      if (r.complete.is_false())
-        r.complete = spot::trival::maybe();
+      if (aut->prop_complete().is_false())
+        aut->prop_complete(spot::trival::maybe());
       // Multiple initial states.  We might need to add a fake one,
       // unless one of the actual initial state has no incoming edge.
-      auto& aut = r.h->aut;
       std::vector<unsigned char> has_incoming(aut->num_states(), 0);
       for (auto& t: aut->edges())
         for (unsigned ud: aut->univ_dests(t))
@@ -2672,6 +2672,9 @@ static void fix_initial_state(result_& r)
             {
               unsigned p = pp.front();
               if (p != init)
+                // FIXME: If p has no incoming we should be able to
+                // change the source of the edges of p instead of
+                // adding new edges.
                 for (auto& t: aut->out(p))
                   aut->new_edge(init, t.dst, t.cond);
             }
@@ -2694,6 +2697,24 @@ static void fix_initial_state(result_& r)
             }
           combiner.new_dests(init, comb_or);
         }
+
+      // Merging two states may break state-based acceptance
+      // make sure all outgoing edges have the same color.
+      if (aut->prop_state_acc().is_true())
+        {
+          bool first = true;
+          spot::acc_cond::mark_t prev;
+          for (auto& e: aut->out(init))
+            if (first)
+              {
+                first = false;
+                prev = e.acc;
+              }
+            else if (e.acc != prev)
+              {
+                e.acc = prev;
+              }
+        }
     }
 }
 
@@ -2871,8 +2892,8 @@ namespace spot
         r.aut_or_ks->set_named_prop("aliases", p);
       }
     fix_acceptance(r);
+    fix_properties(r); // before fix_initial_state
     fix_initial_state(r);
-    fix_properties(r);
     if (r.h->aut && !r.h->aut->is_existential())
       r.h->aut->merge_univ_dests();
     return r.h;

tests/Makefile.am

@@ -1,5 +1,5 @@
 ## -*- coding: utf-8 -*-
-## Copyright (C) 2009-2022 Laboratoire de Recherche et Développement
+## Copyright (C) 2009-2023 Laboratoire de Recherche et Développement
 ## de l'Epita (LRDE).
 ## Copyright (C) 2003-2006 Laboratoire d'Informatique de Paris 6
 ## (LIP6), département Systèmes Répartis Coopératifs (SRC), Université
@@ -223,6 +223,7 @@ TESTS_misc = \
 TESTS_twa = \
   core/385.test \
   core/521.test \
+  core/522.test \
   core/acc.test \
   core/acc2.test \
   core/bdddict.test \

tests/core/522.test

@@ -0,0 +1,43 @@
+#!/bin/sh
+# -*- coding: utf-8 -*-
+# Copyright (C) 2023 Laboratoire de Recherche et Développement de
+# l'Epita (LRDE).
+#
+# 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/>.
+
+. ./defs
+
+set -e
+
+# For issue #522.
+
+cat >552.hoa <<EOF
+HOA: v1
+States: 8
+Start: 0
+Start: 1
+AP: 0
+acc-name: generalized-Buchi 2
+Acceptance: 2 Inf(0)&Inf(1)
+--BODY--
+State: 0 {0} [t] 2 [t] 3 State: 1 {0} [t] 4 [t] 5 State: 2
+{0} [t] 2 [t] 3 State: 3 {0} [t] 6 [t] 7 State: 4 {1} [t] 4 [t] 5
+State: 5 {1} [t] 6 [t] 7 State: 6 [t] 6 [t] 7 State: 7 [t] 6 [t] 7
+--END--
+EOF
+# This command, even without --remove-dead, used to break during print_hoa()
+autfilt --remove-dead 552.hoa > out.hoa
+grep 'States: 7' out.hoa