Use function metadata to specify any Dire functionality you want to use

src/dire/metadata.clj

@@ -0,0 +1,82 @@
+(ns dire.metadata
+  "Functions to allow Dire hooks and conditions to be specified in the
+  metadata of functions, and applied or removed automatically as
+  needed."
+  (:require [dire.core :refer :all]))
+
+;;; Implementation functions
+(defn- apply-dire-wrap-hook!
+  [fn-var hook-fn]
+  (with-wrap-hook! fn-var
+    (-> hook-fn resolve meta :doc)
+    hook-fn))
+
+(defn- apply-dire-eager-pre-hook!
+  [fn-var hook-fn]
+  (with-eager-pre-hook! fn-var
+    (-> hook-fn resolve meta :doc)
+    hook-fn))
+
+(defn- apply-dire-pre!
+  [fn-var possible-handlers pre-cond-fn]
+  (let [pre-cond-name (-> pre-cond-fn resolve meta ::pre-name)
+        correct-handler (first (filter #(= pre-cond-name (-> % resolve meta ::pre-name))
+                                       possible-handlers))]
+    (with-precondition! fn-var
+      (-> pre-cond-fn resolve meta :doc)
+      pre-cond-name
+      pre-cond-fn)
+    (with-handler! fn-var
+      (-> correct-handler resolve meta :doc)
+      {:precondition pre-cond-name}
+      correct-handler)))
+
+(defn- remove-dire-wrap-hook!
+  [fn-var hook-fn]
+  (remove-wrap-hook! fn-var hook-fn))
+
+(defn- remove-dire-eager-pre-hook!
+  [fn-var hook-fn]
+  (remove-eager-pre-hook! fn-var hook-fn))
+
+(defn- remove-dire-pre!
+  [fn-var pre-cond-fn]
+  (let [pre-cond-name (-> pre-cond-fn resolve meta ::pre-name)]
+    (remove-precondition! fn-var pre-cond-name)
+    (remove-handler! fn-var {:precondition pre-cond-name})))
+
+;;; Public API
+(defn apply-dire-meta!
+  [fn-var]
+  (let [preconditions (-> fn-var meta ::preconditions)
+        pre-handlers (-> fn-var meta ::handlers ::pre-handlers)
+        eager-pre-hooks (-> fn-var meta ::eager-pre-hooks)
+        wrap-hooks (-> fn-var meta ::wrap-hooks)]
+    (doall (map #(apply-dire-pre! fn-var pre-handlers %) preconditions))
+    (doall (map #(apply-dire-eager-pre-hook! fn-var %) eager-pre-hooks))
+    (doall (map #(apply-dire-wrap-hook! fn-var %) wrap-hooks))))
+
+(defn remove-dire!
+  [fn-var]
+  (let [preconditions (-> fn-var meta ::preconditions)
+        pre-handlers (-> fn-var meta ::handlers ::pre-handlers)
+        eager-pre-hooks (-> fn-var meta ::eager-pre-hooks)
+        wrap-hooks (-> fn-var meta ::wrap-hooks)]
+    (doall (map #(remove-dire-pre! fn-var %) preconditions))
+    (doall (map #(remove-dire-eager-pre-hook! fn-var %) eager-pre-hooks))
+    (doall (map #(remove-dire-wrap-hook! fn-var %) wrap-hooks))))
+
+;;; Testing code
+(defn precondition {::pre-name :pre} [a b] (prn "precond:") false)
+(defn pre-handler {::pre-name :pre} [_ a b] (prn "handler:"))
+(defn wrap-hook [r [a b]] (prn "wrap:"))
+(defn eager-pre-hook [a b] (prn "eager:"))
+
+(defn ^{::preconditions '[precondition]
+        ::handlers {::pre-handlers '[pre-handler]}
+        ::eager-pre-hooks '[eager-pre-hook]
+        ::wrap-hooks '[wrap-hook]}
+  test-fn
+  "Docstring"
+  [a b]
+  (/ a b))