From f01b0538e153eb8c82441191e3f9776c1352cb90 Mon Sep 17 00:00:00 2001
From: anatoly <tolitius@gmail.com>
Date: Sun, 12 Mar 2017 23:23:59 -0400
Subject: [PATCH] #63: on failure (down) reports and cleans up vs. just "throw"

---
 src/mount/core.cljc        | 21 ++++++++++++++++-----
 src/mount/tools/macro.cljc | 11 ++++++++---
 2 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/src/mount/core.cljc b/src/mount/core.cljc
index af94f4e..cac643a 100644
--- a/src/mount/core.cljc
+++ b/src/mount/core.cljc
@@ -95,12 +95,23 @@
       (swap! running assoc state {:stop stop})
       (update-meta! [state :status] #{:started}))))
 
-(defn- down [state {:keys [stop status] :as current} done]
+(defn- down
+  "brings a state down by
+    * calling its 'stop' function if it is defined
+      * if not defined, state will still become a 'NotStartedState'
+      * in case of a failure on 'stop', state is still marked as :stopped, and the error is logged / printed
+    * dissoc'ing it from the running states
+    * marking it as :stopped"
+  [state {:keys [stop status] :as current} done]
   (when (some status #{:started})
-    (when stop
-      (on-error (str "could not stop [" state "] due to")
-                (record! state stop done)))
-    (alter-state! current (NotStartedState. state))   ;; (!) if a state does not have :stop when _should_ this might leak
+    (if stop
+      (if-let [error (-> (on-error (str "could not stop [" state "] due to")
+                                   (record! state stop done)
+                                   :fail? false)
+                         :f-failed)]
+        (prn error)                                         ;; this would mostly be useful in REPL
+        (alter-state! current (NotStartedState. state)))
+        (alter-state! current (NotStartedState. state)))    ;; (!) if a state does not have :stop when _should_ this might leak
     (swap! running dissoc state)
     (update-meta! [state :status] #{:stopped})))
 
diff --git a/src/mount/tools/macro.cljc b/src/mount/tools/macro.cljc
index dc46e24..0e827b0 100644
--- a/src/mount/tools/macro.cljc
+++ b/src/mount/tools/macro.cljc
@@ -8,14 +8,19 @@
         else)))
 
 #?(:clj
-    (defmacro on-error [msg f]
+    (defmacro on-error [msg f & {:keys [fail?]
+                                 :or {fail? true}}]
       `(if-clj
          (try ~f
               (catch Throwable t#
-                (throw (RuntimeException. ~msg t#))))
+                (if ~fail?
+                  (throw (RuntimeException. ~msg t#))
+                  {:f-failed (ex-info ~msg {} t#)})))
          (try ~f
               (catch :default t#
-                (throw (~'str ~msg " " t#)))))))
+                (if ~fail?
+                  (throw (~'str ~msg " " t#))
+                  {:f-failed (ex-info ~msg {} t#)}))))))
 
 #?(:clj
     (defmacro throw-runtime [msg]