nREPL middleware: only ack the eval after it has finished

Some clients seem to be more sensitive to this than others, but this seems
generally to be the right thing to do.

In the process we stop piggiebacking on the default exec function, thus also
bypassing the session thread in favor of scheduling directly on the game thread.

src/lambdaisland/witchcraft/nrepl/task_eval.clj

@@ -7,30 +7,30 @@
             [nrepl.misc :as misc :refer [response-for]]
             [nrepl.transport :as t]))
 
-(defn run-task [thunk session]
-  (wc/run-task
-   #(if-let [whoami (and (not wc/*default-world*)
-                         (:witchcraft/whoami (meta session)))]
-      (let [player (wc/player whoami)
-            world (wc/world player)]
-        (binding [wc/*default-world* world]
-          (.run thunk)))
-      (.run thunk))))
+(defn scheduled-exec [session]
+  (fn [id ^Runnable thunk ^Runnable ack]
+    (wc/run-task
+     #(if-let [whoami (and (not wc/*default-world*)
+                           (:witchcraft/whoami (meta session)))]
+        (let [player (wc/player whoami)
+              world (wc/world player)]
+          (binding [wc/*default-world* world]
+            (.run thunk)
+            (.run ack)))
+        (do
+          (.run thunk)
+          (.run ack))))))
 
 (defn wrap-eval
   [h]
   (fn [{:keys [op session] :as msg}]
-    (when (and (:exec (meta session))
+    (when (and session
+               (:exec (meta session))
                (not (::decorated (meta session))))
       (alter-meta! session
                    (fn [session-meta]
                      (-> session-meta
-                         (update :exec
-                                 (fn [exec]
-                                   (fn [id thunk ack]
-                                     (exec id
-                                           (partial run-task thunk session)
-                                           ack))))
+                         (assoc :exec (scheduled-exec session))
                          (assoc ::decorated true)))))
     (h msg)))