add order link iterators and fix detected bug

hugr-py/src/hugr/_dfg.py

@@ -76,7 +76,7 @@ def _wire_up(self, node: Node, ports: Iterable[Wire]):
             node_ancestor = _ancestral_sibling(self.hugr, src.node, node)
             if node_ancestor is None:
                 raise NoSiblingAncestor(src.node.idx, node.idx)
-            if node_ancestor != src.node:
+            if node_ancestor != node:
                 self.add_state_order(src.node, node_ancestor)
             self.hugr.add_link(src, node.inp(i))
 

hugr-py/src/hugr/_hugr.py

@@ -283,6 +283,12 @@ def linked_ports(self, port: OutPort | InPort):
 
     # TODO: single linked port
 
+    def outgoing_order_links(self, node: Node) -> Iterable[Node]:
+        return (p.node for p in self.linked_ports(node.out(-1)))
+
+    def incoming_order_links(self, node: Node) -> Iterable[Node]:
+        return (p.node for p in self.linked_ports(node.inp(-1)))
+
     def _node_links(
         self, node: Node, links: dict[_SubPort[P], _SubPort[K]]
     ) -> Iterable[tuple[P, list[K]]]:
@@ -292,7 +298,6 @@ def _node_links(
             return
         # iterate over known offsets
         for offset in range(self.num_ports(node, direction)):
-            # TODO should this also look for -1 state order edges?
             port = cast(P, node.port(offset, direction))
             yield port, list(self._linked_ports(port, links))
 

hugr-py/tests/test_hugr_build.py

@@ -237,9 +237,13 @@ def test_build_inter_graph():
 
     h.set_outputs(nested.root, b)
 
+    _validate(h.hugr, True)
+
     assert _SubPort(h.input_node.out(-1)) in h.hugr._links
     assert h.hugr.num_outgoing(h.input_node) == 2  # doesn't count state order
-    _validate(h.hugr, True)
+    assert len(list(h.hugr.outgoing_order_links(h.input_node))) == 1
+    assert len(list(h.hugr.incoming_order_links(nested.root))) == 1
+    assert len(list(h.hugr.incoming_order_links(h.output_node))) == 0
 
 
 def test_ancestral_sibling():