#22, #25, #26: states with no :stop are restarted on ns recompile

README.md

@@ -421,13 +421,16 @@ Switched to branch 'suspendable'
 Mount will detect when a namespace with states (i.e. with `(defstate ...)`) was reloaded/recompiled, 
 and will check every state in this namespace whether it was running at the point of recompilation. If it was, _it will restart it_:
 
-* will invoke its `:stop` function that was there _before_ the recompilation
-* will invoke its new `:start` function _after_ this state is recompiled/redefined
+* if a state has a `:stop` function, mount will invoke it on the old version of state (i.e. cleanup)
+* it will call a "new" `:start` function _after_ this state is recompiled/redefined
 
 Mount won't keep it a secret, it'll tell you about all the states that had to be restarted during namespace reload/recompilation:
 
 <img src="doc/img/ns-recompile.png" width="500px">
 
+Providing a `:stop` function _is_ optional, but in case a state needs to be cleaned between restarts or on a system shutdown,
+`:stop` is highly recommended.
+
 ## Affected States
 
 Every time a lifecycle function (start/stop/suspend/resume) is called mount will return all the states that were affected:

src/mount/core.cljc

@@ -48,9 +48,10 @@
    this function stops this 'lost' state instance.
    it is meant to be called by defstate before defining a new state"
   [state]
-  (when-let [stop (@running state)]
-    (prn (str "<< stopping.. " state " (namespace was recompiled)"))
-    (stop)
+  (when-let [{:keys [stop] :as up} (@running state)]
+    (when stop
+      (prn (str "<< stopping.. " state " (namespace was recompiled)"))
+      (stop))
     (swap! running dissoc state)
     {:restart? true}))
 
@@ -90,7 +91,7 @@
                         (record! state resume done)
                         (record! state start done)))]
       (alter-state! current s)
-      (swap! running assoc state stop)
+      (swap! running assoc state {:stop stop})
       (update-meta! [state :status] #{:started}))))
 
 (defn- down [state {:keys [stop status] :as current} done]

test/core/mount/test/cleanup_dirty_states.cljc

@@ -31,6 +31,15 @@
       (mount/stop)
       (is (instance? mount.core.NotStartedState (dval tapp.example/nrepl))))))
 
+#?(:clj
+  (deftest start-on-recompile
+    (let [_ (mount/start)
+          before (dval tapp.conf/config)]
+      (require 'tapp.conf :reload)
+      (is (not (identical? before (dval tapp.conf/config))))  ;; should be a newly recompiled map
+      (mount/stop)
+      (is (instance? mount.core.NotStartedState (dval tapp.conf/config))))))
+
 #?(:cljs
   (deftest cleanup-dirty-states
     (let [_ (mount/start #'mount.test.helper/helper)]