Merge pull request #1464 from metabase/cond-as->-macro

Need cond-as-> macro 

.dir-locals.el

@@ -18,6 +18,7 @@
                               (catch-api-exceptions 0)
                               (check 1)
                               (checkp 1)
+                              (cond-as-> 2)
                               (cond-let 0)
                               (conda 0)
                               (context 2)

src/metabase/util.clj

@@ -293,4 +293,24 @@
        (throw (Exception. (format "Timed out after %d milliseconds." ~timeout-ms))))
      result#))
 
+(defmacro cond-as->
+  "Anaphoric version of `cond->`. Binds EXPR to NAME through a series
+   of pairs of TEST and FORM. NAME is successively bound to the value
+   of each FORM whose TEST succeeds.
+
+     (defn maybe-wrap-fn [before after f]
+       (as-> f <>
+         (fn? before) (fn [] (before) (<>))
+         (fn? after)  (fn [] (try (<>)
+                                  (finally (after))))))"
+  {:arglists '([expr nm tst form & more])}
+  [expr nm & clauses]
+  {:pre [(even? (count clauses))]}
+  `(let [~nm ~expr
+         ~@(apply concat (for [[tst form] (partition 2 clauses)]
+                           [nm `(if ~tst
+                                  ~form
+                                  ~nm)]))]
+     ~nm))
+
 (require-dox-in-this-namespace)

test/metabase/test_util.clj

@@ -81,3 +81,24 @@
 
 (expect -7
   ((rpartial - 5 10) 8))
+
+
+;;; ## cond-as->
+(expect 100
+  (cond-as-> 100 <>))
+
+(expect 106
+  (cond-as-> 100 <>
+    true  (+  1 <>)
+    false (+ 10 <>)
+    :ok   (+  5 <>)))
+
+(expect 101
+  (cond-as-> 100 <>
+    (odd? <>)  (inc <>)
+    (even? <>) (inc <>)))
+
+(expect 102
+  (cond-as-> 100 <>
+    (even? <>) (inc <>)
+    (odd? <>)  (inc <>)))