code review: collapse edges should copy the 0-skeleton. A test was added

2 files changed, 7 insertions, 2 deletions

diff --git a/src/python/include/Simplex_tree_interface.h b/src/python/include/Simplex_tree_interface.h
index ad0f9a28..f786ad6e 100644
--- a/src/python/include/Simplex_tree_interface.h
+++ b/src/python/include/Simplex_tree_interface.h
@@ -176,9 +176,12 @@ class Simplex_tree_interface : public Simplex_tree<SimplexTreeOptions> {
       edges = Gudhi::collapse::flag_complex_collapse_edges(edges);
     }
     Simplex_tree_interface* collapsed_stree_ptr = new Simplex_tree_interface();
+    // Copy the original 0-skeleton
+    for (Simplex_handle sh : Base::skeleton_simplex_range(0)) {
+      collapsed_stree_ptr->insert({*(Base::simplex_vertex_range(sh).begin())}, Base::filtration(sh));
+    }
+    // Insert remaining edges
     for (auto remaining_edge : edges) {
-      collapsed_stree_ptr->insert({std::get<0>(remaining_edge)}, 0.);
-      collapsed_stree_ptr->insert({std::get<1>(remaining_edge)}, 0.);
       collapsed_stree_ptr->insert({std::get<0>(remaining_edge), std::get<1>(remaining_edge)}, std::get<2>(remaining_edge));
     }
     return collapsed_stree_ptr;
diff --git a/src/python/test/test_simplex_tree.py b/src/python/test/test_simplex_tree.py
index 30a8f5e0..83be0602 100755
--- a/src/python/test/test_simplex_tree.py
+++ b/src/python/test/test_simplex_tree.py
@@ -356,3 +356,5 @@ def test_collapse_edges():
     st.collapse_edges()
     assert st.num_simplices() == 9
     assert st.find([1, 3]) == False
+    for simplex in st.get_skeleton(0): 
+        assert simplex[1] == 1.