Handle no-path edge case in routeCost export; add backwards-compat comment

Agent-Logs-Url: https://github.com/steffenaxer/matsim-libs/sessions/facab8bc-3da3-42ec-9057-355df02c7305

Co-authored-by: steffenaxer <26229392+steffenaxer@users.noreply.github.com>

Author: Copilot

matsim/src/main/java/org/matsim/core/router/speedy/CHQueryExporter.java

@@ -273,9 +273,14 @@ private static void exportJSON(SpeedyGraph graph, CHGraph chGraph, SpeedyALTData
                 }
                 pw.println("  ],");
 
-                // Route cost and link count
-                pw.printf(Locale.US, "  \"routeCost\": %.4f,%n", chResult.routeCost);
-                pw.printf("  \"routeLinks\": %d,%n", chResult.pathLinks.size());
+                // Route cost and link count (null when no path found)
+                if (Double.isFinite(chResult.routeCost) && !chResult.pathLinks.isEmpty()) {
+                    pw.printf(Locale.US, "  \"routeCost\": %.4f,%n", chResult.routeCost);
+                    pw.printf("  \"routeLinks\": %d,%n", chResult.pathLinks.size());
+                } else {
+                    pw.println("  \"routeCost\": null,");
+                    pw.println("  \"routeLinks\": 0,");
+                }
 
                 // Shortcut tree (for first CH edge only if available)
                 pw.print("  \"shortcutTree\": ");

matsim/tools/ch-viz/ch-visualization.html

@@ -1076,6 +1076,7 @@ <h2>Search Space Comparison</h2>
   document.getElementById('ch-total').textContent    = chN.toLocaleString();
   document.getElementById('ch-times').textContent    = times;
   // Route result info
+  // Route result info (routeLinks/routeCost added in latest exporter; fall back to pathLinks for older JSON)
   const links = query.routeLinks ?? (query.pathLinks ? query.pathLinks.length : '-');
   const cost  = query.routeCost != null ? query.routeCost.toFixed(1) + 's' : '-';
   document.getElementById('route-links').textContent = links.toLocaleString ? links.toLocaleString() : links;