Tweaks

README

@@ -53,7 +53,7 @@ Here are some specific complexity issues that I've found:
   request.
 
   2. Often the data you need in one part of the control flow isn't
-  visible because it is created and consumed elsehwere.
+  visible because it is created and consumed elsewhere.
 
   3. What you need to compute tends to not change much, but how you
   compute it often does. That is, new bits of data become relavent,

src/kiln/kiln.clj

@@ -28,6 +28,14 @@
       (:cleanup-success clay)
       (:cleanup-failure clay)))
 
+(defn- run-clay
+  [kiln clay]
+  (try
+    (dosync (alter (:vals kiln) assoc (:id clay) ::running))
+    ((:fun clay) kiln)
+    (finally
+     (dosync (alter (:vals kiln) assoc (:id clay) nil)))))
+
 (defn fire
   "Run the clay within the kiln to compute/retrieve its value."
   [kiln clay] ; the clay can be a coal
@@ -46,8 +54,7 @@
        (if (::clay? clay)
          (do (when-let [pres (:pre-compute clay)]
                (doseq [pre pres] (fire kiln pre)))
-             (dosync (alter (:vals kiln) assoc (:id clay) ::running))
-             (let [result ((:fun clay) kiln)]
+             (let [result (run-clay kiln clay)]
                (dosync
                 (alter (:vals kiln) assoc (:id clay) result)
                 (when (has-cleanup? clay)

test/kiln/kiln_test.clj

@@ -1,5 +1,6 @@
 (ns kiln.kiln-test
   (use clojure.test)
+  (use slingshot.slingshot)
   (use kiln.kiln))
 
 (deftest test-new-kiln
@@ -85,6 +86,18 @@
     (fire k bob!)
     (is (= @store [k]))))
 
+(declare loopy-clay)
+(defclay loopy-clay (?? loopy-clay))
+
+(deftest test-loopy-clay
+  (let [k (new-kiln)]
+    (is (= :exception-thrown
+           (try+
+            (fire k loopy-clay)
+            (catch [:type :kiln-loop] {:keys [clay kiln]}
+              (is (= clay loopy-clay))
+              (is (= kiln k))
+              :exception-thrown))))))
 
 (comment