Add readable/spyf

Author: ataggart

CHANGELOG.md

@@ -6,6 +6,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ([despite its flaws](https://www.youtube.com/watch?v=oyLBGkS5ICk)).
 
 ## [Unreleased]
+### Added 
+- Add implementation of `spyf` to `clojure.tools.logging.readable`.
+
 ### Changed
 - Decreased the per-call overhead when using SLF4J, Commons Logging, and Log4j2.
   Previously, their associated `logger-factory` implementations were calling

src/main/clojure/clojure/tools/logging/readable.clj

@@ -159,3 +159,13 @@
   {:arglists '([fmt & fmt-args] [throwable fmt & fmt-args])}
   [& args]
   `(logf :fatal ~@args))
+
+(defmacro spyf
+  "Evaluates expr and may write (logf level fmt result) to the log. Returns the
+  result of expr. Defaults to :debug log level."
+  ([fmt expr]
+   `(spyf :debug ~fmt ~expr))
+  ([level fmt expr]
+   `(let [a# ~expr]
+      (logf ~level ~fmt a#)
+      a#)))

src/test/clojure/clojure/tools/logging/test_readable.clj

@@ -188,6 +188,18 @@
       (is (logged? "clojure.tools.logging.test-readable" :debug e "hello \"world\"")))))
 
 
+(deftest spyf-default
+  (with-log
+    (spyf "result: %s" (str "hello" " " "world"))
+    (is (logged? "clojure.tools.logging.test-readable" :debug nil "result: \"hello world\""))))
+
+(deftest spyf-level
+  (doseq [level #{:trace :debug :info :warn :error :fatal}]
+    (with-log
+      (spyf level "result: %s" (str "hello" " " "world"))
+      (is (logged? "clojure.tools.logging.test-readable" level nil "result: \"hello world\"")))))
+
+
 (deftest println-style
   (are [f kw] (with-log
                 (f "hello" "world")