Fix a few minor bugs

Found by trying to run poor_mans_visualisation :-)

birdvisu/annotations/analysis.py

@@ -8,6 +8,7 @@ from ..topo_v3 import MetricType
 import heapq
 from enum import Enum
 from functools import total_ordering
+from collections import defaultdict
 
 class TopologyDifference(Annotator):
 	"""Finds differences between ancestors.
@@ -51,16 +52,19 @@ class TopologyDifference(Annotator):
 		newe = new.edges
 		only_old = olde - newe
 		only_new = newe - olde
-		common = olde & newe
-		discrepant = set()
-		for edge in common:
-			o = old.edges[edge]
-			n = new.edges[edge]
-			if o != n: discrepant.add(edge)
+		# Note: edge can not be discrepant, since it is determined by all its
+		# details. However, it is useful to highlight edges with changed cost.
+		changed_cost_old: dict[tuple[VertexID, VertexID], list[Edge]] = defaultdict(lambda: [])
+		for e in only_old: changed_cost_old[(e.source, e.target)].append(e)
+		changed_cost_new: dict[tuple[VertexID, VertexID], list[Edge]] = defaultdict(lambda: [])
+		for e in only_new: changed_cost_new[(e.source, e.target)].append(e)
+
 		for e in only_old: result.for_edge[e] = self.Status.Missing
 		for e in only_new: result.for_edge[e] = self.Status.New
-		for e in discrepant: result.for_edge[e] = self.Status.Discrepant
-
+		for k in changed_cost_old.keys() & changed_cost_new.keys():
+			# We override the New/Missing status in this case.
+			for e in changed_cost_old[k]: result.for_edge[e] = self.Status.Discrepant
+			for e in changed_cost_new[k]: result.for_edge[e] = self.Status.Discrepant
 		return result
 
 class ShortestPathTree(Annotator):

birdvisu/topo_v3.py

@@ -266,7 +266,7 @@ class VertexFinder:
 		if not topo.frozen: raise ValueError("Can only add frozen topologies.")
 		if topo in self.topologies: raise KeyError("This topology is already in the finder")
 		self.topologies.append(topo)
-		for v in topo.vertices:
+		for v in topo.vertices.values():
 			id = v.id
 			self.vertices[id].append(topo)
 			# Add to various "indices"