Tidy up some details

Closes #1725

Author: jeromekelleher

c/tskit/trees.c

@@ -3626,7 +3626,6 @@ tsk_tree_get_time(const tsk_tree_t *self, tsk_id_t u, double *t)
     if (u == self->virtual_root) {
         *t = INFINITY;
     } else {
-
         ret = tsk_treeseq_get_node(self->tree_sequence, u, &node);
         if (ret != 0) {
             goto out;
@@ -4288,7 +4287,7 @@ tsk_tree_get_size_bound(const tsk_tree_t *self)
 /* Traversal orders */
 
 static tsk_id_t *
-tsk_tree_alloc_stack(const tsk_tree_t *self)
+tsk_tree_alloc_node_stack(const tsk_tree_t *self)
 {
     return tsk_malloc(tsk_tree_get_size_bound(self) * sizeof(tsk_id_t));
 }
@@ -4300,7 +4299,7 @@ tsk_tree_preorder(
     int ret = 0;
     const tsk_id_t *restrict right_child = self->right_child;
     const tsk_id_t *restrict left_sib = self->left_sib;
-    tsk_id_t *restrict stack = tsk_tree_alloc_stack(self);
+    tsk_id_t *restrict stack = tsk_tree_alloc_node_stack(self);
     tsk_size_t num_nodes = 0;
     tsk_id_t u, v;
     int stack_top;
@@ -4352,7 +4351,7 @@ tsk_tree_postorder(
     const tsk_id_t *restrict right_child = self->right_child;
     const tsk_id_t *restrict left_sib = self->left_sib;
     const tsk_id_t *restrict parent = self->parent;
-    tsk_id_t *restrict stack = tsk_tree_alloc_stack(self);
+    tsk_id_t *restrict stack = tsk_tree_alloc_node_stack(self);
     tsk_size_t num_nodes = 0;
     tsk_id_t u, v, postorder_parent;
     int stack_top;

python/tests/test_highlevel.py

@@ -445,6 +445,24 @@ def get_samples(ts, time=None, population=None):
 
 
 class TestTreeTraversals:
+    def test_bad_traversal_order(self):
+        ts = msprime.sim_ancestry(2, random_seed=234)
+        tree = ts.first()
+        for bad_order in ["pre", "post", "preorderorder", ("x",), b"preorder"]:
+            with pytest.raises(ValueError, match="Traversal order"):
+                tree.nodes(order=bad_order)
+
+    @pytest.mark.parametrize("order", list(traversal_map.keys()))
+    def test_returned_types(self, order):
+        ts = msprime.sim_ancestry(2, random_seed=234)
+        tree = ts.first()
+        iterator = tree.nodes(order=order)
+        assert isinstance(iterator, collections.abc.Iterable)
+        lst = list(iterator)
+        assert len(lst) > 0
+        for u in lst:
+            assert isinstance(u, int)
+
     @pytest.mark.parametrize("ts", get_example_tree_sequences())
     @pytest.mark.parametrize("order", list(traversal_map.keys()))
     def test_traversals_virtual_root(self, ts, order):

python/tskit/trees.py

@@ -2127,9 +2127,11 @@ def timedesc(self, u=NULL):
         return self.timeasc(u)[::-1]
 
     def _preorder_traversal(self, root):
+        # Return Python integers for compatibility
         return map(int, self.preorder(root))
 
     def _postorder_traversal(self, root):
+        # Return Python integers for compatibility
         return map(int, self.postorder(root))
 
     def _inorder_traversal(self, root):
@@ -2166,13 +2168,13 @@ def _timeasc_traversal(self, root):
         """
         Sorts by increasing time but falls back to increasing ID for equal times.
         """
-        yield from self.timeasc(root)
+        return map(int, self.timeasc(root))
 
     def _timedesc_traversal(self, root):
         """
         The reverse of timeasc.
         """
-        yield from self.timedesc(root)
+        return map(int, self.timedesc(root))
 
     def _minlex_postorder_traversal(self, root):
         """