remove_fin: fix incorrect state-based output

* spot/twaalgos/remfin.cc: If no Inf set is used, set sbacc early so
that it is used in the algorithm.
* tests/core/remfin.test: Add more tests.
* NEWS: Mention the bug.

NEWS

@@ -194,6 +194,13 @@ New in spot 2.3.5.dev (not yet released)
   - The 'spot.gen' package exports the functions from libspotgen.
     See https://spot.lrde.epita.fr/ipynb/gen.html for examples.
 
+  Bugs fixed:
+
+  - When the remove_fin() function was called on some automaton with
+    Inf-less acceptance involving at least one disjunction (e.g.,
+    generalized co-Büchi), it would sometime output an automaton with
+    transition-based acceptance but marked as state-based.
+
   Backward-incompatible changes:
 
   - spot::acc_cond::mark_t::operator bool() has been marked as

spot/twaalgos/remfin.cc

@@ -27,7 +27,7 @@
 #include <spot/twaalgos/alternation.hh>
 #include "spot/priv/enumflags.hh"
 
-//#define TRACE
+// #define TRACE
 #ifdef TRACE
 #define trace std::cerr
 #else
@@ -672,7 +672,11 @@ namespace spot
       res->set_acceptance(aut->num_sets() + extra_sets, new_code);
       res->set_init_state(aut->get_init_state_number());
 
-      bool sbacc = aut->prop_state_acc().is_true();
+      // If the input had no Inf, the output is a state-based automaton.
+      if (allinf == 0U)
+        res->prop_state_acc(true);
+
+      bool sbacc = res->prop_state_acc().is_true();
       scc_info si(aut);
       unsigned nscc = si.scc_count();
       std::vector<unsigned> state_map(nst);
@@ -749,9 +753,6 @@ namespace spot
               }
         }
 
-      // If the input had no Inf, the output is a state-based automaton.
-      if (allinf == 0U)
-        res->prop_state_acc(true);
 
       res->purge_dead_states();
       trace << "before cleanup: " << res->get_acceptance() << '\n';

tests/core/remfin.test

@@ -250,6 +250,20 @@ State: 1 {2}
 [0] 1
 [!0] 0
 --END--
+/*
+** This random automaton caused remove_fin() to output
+** an automaton with transition-based acceptance incorrectly marked as
+** state-based.
+*/
+HOA: v1 States: 10 Start: 0 AP: 2 "p0" "p1" Acceptance: 4 Fin(1) |
+(Fin(2) & Fin(3) & Fin(0)) properties: trans-labels explicit-labels
+trans-acc --BODY-- State: 0 [!0&1] 5 [!0&1] 7 State: 1 [0&!1] 2 {2}
+[0&1] 9 {1} [!0&1] 1 [0&!1] 6 {1 3} State: 2 [!0&1] 8 {0 1} [!0&!1]
+1 {1} State: 3 [!0&1] 5 {1} [0&1] 2 State: 4 [0&!1] 4 {1} [0&1] 6 {0}
+[0&1] 5 {1} State: 5 [0&1] 9 {1} State: 6 [0&1] 5 {2 3} [!0&1] 9 {2}
+[!0&1] 4 State: 7 [0&!1] 8 {3} [!0&!1] 7 {2} [0&!1] 3 {2} [!0&1] 5 {1}
+State: 8 [!0&1] 8 {2} [!0&!1] 3 {1} [!0&1] 4 State: 9 [0&!1] 6 {0 3}
+[!0&1] 2 --END--
 EOF
 
 acctwelve='Inf(0)&Inf(1)&Inf(2)&Inf(3)&Inf(4)&Inf(5)'
@@ -715,6 +729,91 @@ State: 1 {0}
 [!0] 0
 [0] 1
 --END--
+HOA: v1
+States: 21
+Start: 0
+AP: 2 "p0" "p1"
+acc-name: Buchi
+Acceptance: 1 Inf(0)
+properties: trans-labels explicit-labels state-acc
+--BODY--
+State: 0 {0}
+[!0&1] 5
+[!0&1] 7
+State: 1
+[!0&1] 1
+[0&!1] 2
+[0&!1] 6
+[0&1] 9
+[!0&1] 14
+[!0&1] 20
+State: 2
+[!0&!1] 1
+[!0&1] 8
+[!0&!1] 20
+State: 3
+[0&1] 2
+[!0&1] 5
+[0&1] 18
+State: 4
+[0&!1] 4
+[0&1] 5
+[0&1] 6
+[0&!1] 17
+State: 5
+[0&1] 9
+State: 6
+[!0&1] 4
+[0&1] 5
+[!0&1] 9
+[!0&1] 12
+[!0&1] 17
+State: 7 {0}
+[0&!1] 3
+[!0&1] 5
+[!0&!1] 7
+[0&!1] 8
+State: 8
+[!0&!1] 3
+[!0&1] 4
+[!0&1] 8
+[!0&1] 12
+[!0&1] 13
+[!0&1] 17
+[!0&!1] 19
+State: 9
+[!0&1] 2
+[0&!1] 6
+[0&!1] 11
+[!0&1] 18
+State: 10 {0}
+[0&!1] 11
+State: 11 {0}
+[!0&1] 10
+[!0&1] 12
+State: 12 {0}
+[0&1] 11
+State: 13 {0}
+[!0&1] 12
+[!0&1] 13
+State: 14 {0}
+[!0&1] 14
+State: 15 {0}
+[0&1] 16
+State: 16 {0}
+[!0&1] 18
+State: 17 {0}
+[0&1] 15
+[0&!1] 17
+State: 18 {0}
+[!0&!1] 20
+State: 19 {0}
+[!0&1] 15
+[0&1] 18
+State: 20 {0}
+[0&1] 16
+[!0&1] 20
+--END--
 EOF
 
 cat >expected-tgba <<EOF
@@ -1174,6 +1273,91 @@ State: 1 {0}
 [!0] 0
 [0] 1
 --END--
+HOA: v1
+States: 21
+Start: 0
+AP: 2 "p0" "p1"
+acc-name: Buchi
+Acceptance: 1 Inf(0)
+properties: trans-labels explicit-labels trans-acc
+--BODY--
+State: 0
+[!0&1] 5
+[!0&1] 7
+State: 1
+[!0&1] 1
+[0&!1] 2
+[0&!1] 6
+[0&1] 9
+[!0&1] 14
+[!0&1] 20
+State: 2
+[!0&!1] 1
+[!0&1] 8
+[!0&!1] 20
+State: 3
+[0&1] 2
+[!0&1] 5
+[0&1] 18
+State: 4
+[0&!1] 4
+[0&1] 5
+[0&1] 6
+[0&!1] 17
+State: 5
+[0&1] 9
+State: 6
+[!0&1] 4
+[0&1] 5
+[!0&1] 9
+[!0&1] 12
+[!0&1] 17
+State: 7
+[0&!1] 3
+[!0&1] 5
+[!0&!1] 7 {0}
+[0&!1] 8
+State: 8
+[!0&!1] 3
+[!0&1] 4
+[!0&1] 8
+[!0&1] 12
+[!0&1] 13
+[!0&1] 17
+[!0&!1] 19
+State: 9
+[!0&1] 2
+[0&!1] 6
+[0&!1] 11
+[!0&1] 18
+State: 10
+[0&!1] 11 {0}
+State: 11
+[!0&1] 10 {0}
+[!0&1] 12 {0}
+State: 12
+[0&1] 11 {0}
+State: 13
+[!0&1] 12
+[!0&1] 13 {0}
+State: 14
+[!0&1] 14 {0}
+State: 15
+[0&1] 16
+State: 16
+[!0&1] 18 {0}
+State: 17
+[0&1] 15
+[0&!1] 17 {0}
+State: 18
+[!0&!1] 20 {0}
+State: 19
+[!0&1] 15
+[0&1] 18
+State: 20
+[0&1] 16 {0}
+[!0&1] 20 {0}
+--END--
 EOF
 
 run 0 $autfilt -H --remove-fin test1 > output
@@ -1183,3 +1367,10 @@ diff -u output expected
 run 0 $autfilt -H --tgba test1 > output
 cat output
 diff -u output expected-tgba
+
+# make sure the above expected automata are correct
+autcross --language-preserved 'autfilt --remove-fin' 'autfilt --tgba' -Ftest1
+
+# try 10 small random automata just in case
+randaut -A'random 6' -Q10 -n10 3 |
+autcross --verbose --language-preserved 'autfilt --remove-fin' 'autfilt --tgba'