Add ring.util.async/raising function

Closes #403.

ring-core/src/ring/util/async.clj

@@ -0,0 +1,12 @@
+(ns ring.util.async)
+
+(defn raising
+  "Alter function f to catch all Throwable errors and pass them to the raise
+  function. Designed for use with asynchronous handlers, particularly in
+  wrapping a respond argument to a 3-arity handler."
+  {:added "1.12"}
+  [raise f]
+  (fn [& args]
+    (try
+      (apply f args)
+      (catch Throwable t (raise t)))))

ring-core/test/ring/util/test/async.clj

@@ -0,0 +1,9 @@
+(ns ring.util.test.async
+  (:require [clojure.test :refer [deftest is]]
+            [ring.util.async :refer [raising]]))
+
+(deftest test-raising
+  (let [error (promise)]
+    ((raising error #(/ 1 0)))
+    (is (realized? error))
+    (is (instance? ArithmeticException (deref error 0 nil)))))