BUGFIX: resolve-route-and-navigate! drops params on cross-chart targets

Guide.adoc

@@ -1627,7 +1627,8 @@ URL encoding and decoding is handled by the `URLCodec` protocol defined in `rout
     "Given a context map, return a URL path string (with query if needed).
      Context keys: :segments, :params, :route-elements")
   (decode-url [this href route-elements]
-    "Given a URL string and route-elements map, return {:leaf-id :params} or nil."))
+    "Given a URL string and route-elements map, return {:leaf-id :params}, or nil.
+     May return {:params <map>} without :leaf-id for cross-chart targets."))
 -----
 
 ==== Default: TransitBase64Codec

src/main/com/fulcrologic/statecharts/integration/fulcro/routing.cljc

@@ -986,8 +986,8 @@
   [app elements-by-id provider codec]
   (let [href    (ruh/current-href provider)
         decoded (ruc/decode-url codec href elements-by-id)]
-    (if decoded
-      (let [{:keys [leaf-id params]} decoded
+    (if-let [leaf-id (:leaf-id decoded)]
+      (let [{:keys [params]} decoded
             route-params (when params
                            (reduce-kv (fn [acc _state-id state-params]
                                         (merge acc state-params))
@@ -996,12 +996,16 @@
         leaf-id)
       ;; Codec didn't match directly — try reachable targets via deep search
       ;; (needed for cross-chart :route/reachable targets not in this chart's elements)
-      (let [segments  (ruh/current-url-path href)
-            leaf-name (peek segments)]
+      (let [segments    (ruh/current-url-path href)
+            leaf-name   (peek segments)
+            route-params (when-let [params (:params decoded)]
+                           (reduce-kv (fn [acc _state-id state-params]
+                                        (merge acc state-params))
+                             {} params))]
         (when leaf-name
           (when-let [{:keys [target-key child?]} (ruh/find-target-by-leaf-name-deep elements-by-id leaf-name)]
             (when child?
-              (route-to! app target-key {})
+              (route-to! app target-key (or route-params {}))
               target-key)))))))
 
 (defn install-url-sync!

src/main/com/fulcrologic/statecharts/integration/fulcro/routing/url_codec.cljc

@@ -33,7 +33,9 @@
      Context keys: :segments (vector of state IDs), :params (map keyed by state-id),
      :route-elements (map of state-id -> element map).")
   (decode-url [this href route-elements]
-    "Given a URL string and route-elements map, return {:leaf-id <state-id> :params <map>}."))
+    "Given a URL string and route-elements map, return {:leaf-id <state-id> :params <map>},
+     or nil. May return {:params <map>} without :leaf-id when params are present but the
+     leaf segment doesn't match a known route element (e.g. cross-chart targets)."))
 
 ;; ---------------------------------------------------------------------------
 ;; Path generation from active configuration (state -> URL)

src/main/com/fulcrologic/statecharts/integration/fulcro/routing/url_codec_transit.cljc

@@ -143,7 +143,7 @@
                                       (= (url-codec/element-segment element) leaf-name))
                                 id))
                         route-elements))]
-      (when leaf-id
+      (when (or leaf-id params)
         {:leaf-id leaf-id
          :params  params}))))
 

src/test/com/fulcrologic/statecharts/integration/fulcro/routing/simulated_history_spec.cljc

@@ -396,12 +396,12 @@
         "decodes leaf matching by :route/segment"
         (:leaf-id decoded) => :page-b)))
 
-  (component "decode returns nil for unrecognized URL"
+  (component "decode returns nil for unrecognized URL without params"
     (let [codec          (ruct/transit-base64-codec)
           route-elements {:page-a {:route/target 'com.example/PageA}}
           decoded        (ruc/decode-url codec "/unknown/path" route-elements)]
       (assertions
-        "returns nil when no route element matches the leaf segment"
+        "returns nil when no route element matches and no params present"
         decoded => nil)))
 
   (component "single segment route"