twa_graph: introduce copy_state_names_from()

* spot/twa/twagraph.cc, spot/twa/twagraph.hh: Here.  Also
make sure "original-states" survives defrag_states().
* NEWS: Mention it.
* tests/python/origstate.py: New file.
* tests/Makefile.am: Add it.

NEWS

@@ -62,6 +62,10 @@ New in spot 2.3.3.dev (not yet released)
   - The 'spot.gen' package exports the functions from libspotgen.
     See https://spot.lrde.epita.fr/ipynb/gen.html for examples.
 
+  - twa_graph::copy_state_names_from() can be used to copy the state
+    names from another automaton, honoring "original-states" if
+    present.
+
   Bugs fixed:
 
   - the transformation to state-based acceptance (spot::sbacc()) was

spot/twa/twagraph.cc

@@ -542,6 +542,7 @@ namespace spot
             unsigned dst = newst[s];
             if (dst == s || dst == -1U)
               continue;
+            assert(dst < s);
             (*names)[dst] = std::move((*names)[s]);
           }
         names->resize(used_states);
@@ -558,6 +559,19 @@ namespace spot
           }
         std::swap(*hs, hs2);
       }
+    if (auto os = get_named_prop<std::vector<unsigned>>("original-states"))
+      {
+        unsigned size = os->size();
+        for (unsigned s = 0; s < size; ++s)
+          {
+            unsigned dst = newst[s];
+            if (dst == s || dst == -1U)
+              continue;
+            assert(dst < s);
+            (*os)[dst] = (*os)[s];
+          }
+        os->resize(used_states);
+      }
     init_number_ = newst[init_number_];
     g_.defrag_states(std::move(newst), used_states);
   }
@@ -582,5 +596,30 @@ namespace spot
       }
   }
 
+  void twa_graph::copy_state_names_from(const const_twa_graph_ptr& other)
+  {
+    if (other == shared_from_this())
+      return;
+    auto orig = get_named_prop<std::vector<unsigned>>("original-states");
+    if (orig && orig->size() != num_states())
+      throw std::runtime_error("copy_state_names_from(): unexpected size "
+                               "for original-states");
+
+    auto names = std::unique_ptr<std::vector<std::string>>
+      (new std::vector<std::string>);
+    unsigned ns = num_states();
+    unsigned ons = other->num_states();
+
+    for (unsigned s = 0; s < ns; ++s)
+      {
+        unsigned other_s = orig ? (*orig)[s] : s;
+        if (other_s >= ons)
+          throw std::runtime_error("copy_state_names_from(): state does not"
+                                   " exist in source automaton");
+        names->emplace_back(other->format_state(other_s));
+      }
+
+    set_named_prop("state-names", names.release());
+  }
 
 }

spot/twa/twagraph.hh

@@ -566,6 +566,14 @@ namespace spot
     /// automaton, those that are not actually used by its labels.
     void remove_unused_ap();
 
+    /// \brief Define the state names of this automaton using
+    /// the names from \a other.
+    ///
+    /// If the "original-states" named property is set, it is used to
+    /// map the state numbers, otherwise an identity mapping is
+    /// assumed.
+    void copy_state_names_from(const const_twa_graph_ptr& other);
+
     acc_cond::mark_t state_acc_sets(unsigned s) const
     {
       if (SPOT_UNLIKELY(!(bool)prop_state_acc()))

tests/Makefile.am

@@ -346,6 +346,7 @@ TESTS_python = \
   python/minato.py \
   python/misc-ec.py \
   python/optionmap.py \
+  python/origstate.py \
   python/otfcrash.py \
   python/parsetgba.py \
   python/prodexpt.py \

tests/python/origstate.py

@@ -0,0 +1,108 @@
+# -*- mode: python; coding: utf-8 -*-
+# Copyright (C) 2015, 2017  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
+from sys import exit
+
+aut = spot.automaton("""
+HOA: v1
+States: 2
+Start: 0
+AP: 2 "a" "b"
+acc-name: Buchi
+Acceptance: 1 Inf(0)
+--BODY--
+State: 0
+[0] 0 {0}
+[!0] 0
+[1] 1
+State: 1
+[1] 1 {0}
+--END--
+""")
+
+aut2 = spot.degeneralize(aut)
+assert aut2.to_str() == """HOA: v1
+States: 3
+Start: 0
+AP: 2 "a" "b"
+acc-name: Buchi
+Acceptance: 1 Inf(0)
+properties: trans-labels explicit-labels state-acc
+--BODY--
+State: 0 {0}
+[0] 0
+[!0] 1
+[1] 2
+State: 1
+[0] 0
+[!0] 1
+[1] 2
+State: 2 {0}
+[1] 2
+--END--"""
+
+aut2.copy_state_names_from(aut)
+assert aut2.to_str() == """HOA: v1
+States: 3
+Start: 0
+AP: 2 "a" "b"
+acc-name: Buchi
+Acceptance: 1 Inf(0)
+properties: trans-labels explicit-labels state-acc
+--BODY--
+State: 0 "0" {0}
+[0] 0
+[!0] 1
+[1] 2
+State: 1 "0"
+[0] 0
+[!0] 1
+[1] 2
+State: 2 "1" {0}
+[1] 2
+--END--"""
+
+aut2.set_init_state(2)
+aut2.purge_unreachable_states()
+ref = """HOA: v1
+States: 1
+Start: 0
+AP: 2 "a" "b"
+acc-name: Buchi
+Acceptance: 1 Inf(0)
+properties: trans-labels explicit-labels state-acc colored
+properties: deterministic
+--BODY--
+State: 0 "1" {0}
+[1] 0
+--END--"""
+assert aut2.to_str() == ref
+# This makes sure that the original-states vector has also been renamed.
+aut2.copy_state_names_from(aut)
+assert aut2.to_str() == ref
+
+aut2 = spot.degeneralize(aut)
+aut2.release_named_properties()
+try:
+    aut2.copy_state_names_from(aut)
+except RuntimeError as e:
+    assert "state does not exist in source automaton" in str(e)
+else:
+    exit(1)