Merge branch 'report_weight_in_yen' into enum_cycle_undirected

Author: kappybar

src/sage/graphs/path_enumeration.pyx

@@ -735,6 +735,12 @@ def yen_k_shortest_simple_paths(self, source, target, weight_function=None,
          [1, 6, 9, 3, 4, 5],
          [1, 6, 9, 11, 10, 5]]
 
+    When ``s == t`` and ``report_edge == True`` and ``report_weight == True`` (:issue:`40247`)::
+
+        sage: g = DiGraph([(1, 2)])
+        sage: list(yen_k_shortest_simple_paths(g, 1, 1, report_edges=True, report_weight=True))
+        [(0, [])]
+
     No path between two vertices exists::
 
         sage: g = Graph(2)
@@ -747,12 +753,8 @@ def yen_k_shortest_simple_paths(self, source, target, weight_function=None,
         raise ValueError("vertex '{}' is not in the graph".format(target))
 
     if source == target:
-        if report_edges:
-            yield []
-        elif report_weight:
-            yield (0, [source])
-        else:
-            yield [source]
+        P = [] if report_edges else [source]
+        yield (0, P) if report_weight else P
         return
 
     if self.has_loops() or self.allows_multiple_edges():