EDN-serialize vars etc by modifying printing.

Use the letterpress library to provide tagged literal printed forms for
vars, classes, and regular expressions.  Use standard Clojure data
readers to reconstitute these forms as the appropriate values.  This
removes the need for a custom EDN reader implementation.

Author: llasram

LICENSE

@@ -200,236 +200,3 @@
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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    limitations under the License.
-
---------------------------------------------------------------------------------
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README.md

@@ -87,9 +87,6 @@ Copyright © 2013-2014 Marshall Bockrath-Vandegrift & Damballa, Inc.
 
 Distributed under the Apache License, Version 2.0.
 
-The EDN reader implementation (`EdnReader.java`) is copyright © 2013 Rich
-Hickey, and is distributed under the Eclipse Public License v1.0.
-
 [intro]: https://github.com/damballa/parkour/blob/master/doc/intro.md
 [motivation]: https://github.com/damballa/parkour/blob/master/doc/motivation.md
 [namespaces]: https://github.com/damballa/parkour/blob/master/doc/namespaces.md

project.clj

@@ -17,6 +17,7 @@
   :dependencies [[org.clojure/tools.logging "0.3.1"]
                  [com.damballa/abracad "0.4.11"]
                  [org.apache.avro/avro "1.7.7"]
+                 [org.platypope/letterpress "0.1.0"]
                  [pjstadig/scopes "0.3.0"]
                  [transduce/transduce "0.1.1"]]
   :plugins [[codox/codox "0.6.6"]]

src/clojure/parkour/cser.clj

@@ -1,11 +1,14 @@
 (ns parkour.cser
   (:refer-clojure :exclude [assoc! get read-string pr-str])
   (:require [clojure.core :as cc]
-            [parkour.conf :as conf])
+            [clojure.edn :as edn]
+            [letterpress.core :as lp]
+            [parkour.conf :as conf]
+            [parkour.cser.readers :refer [data-readers]]
+            [parkour.cser.printers :refer [data-printers]])
   (:import [java.io Writer]
            [clojure.lang RT]
-           [org.apache.hadoop.conf Configuration]
-           [parkour.edn EdnReader]))
+           [org.apache.hadoop.conf Configuration]))
 
 (def ^:internal ^:dynamic *conf*
   "Configuration of job being executed/configured during job configuration
@@ -18,23 +21,34 @@ de/serialization."
 
 (defn ^:private read-string*
   "Like core `edn/read-string`, but using cser/EDN reader implementation."
-  ([s] (read-string* {:eof nil, :readers *data-readers*} s))
-  ([opts s] (when s (EdnReader/readString s opts))))
+  ([s] (read-string* {} s))
+  ([opts s]
+     (let [readers (merge *data-readers* data-readers (:readers opts))
+           opts (assoc opts :readers readers)]
+       (edn/read-string opts s))))
 
 (defn read-string
   "Like core `edn/read-string`, but using cser/EDN reader implementation in the
 cser context of `conf`."
   ([conf s] (with-conf conf (read-string* s)))
   ([conf opts s] (with-conf conf (read-string* opts s))))
 
+(defn ^:private pr-str*
+  "Like core `pr-str`, but with cser-specific printers."
+  ([] "")
+  ([x] (lp/pr-str {:printers data-printers} x))
+  ([x & xs] (apply lp/pr-str {:printers data-printers} x xs)))
+
 (defn pr-str
   "Like core `pr-str`, but in the cser context of `conf`."
-  [conf & xs] (with-conf conf (apply cc/pr-str xs)))
+  ([conf] "")
+  ([conf x] (with-conf conf (pr-str* x)))
+  ([conf x & xs] (with-conf conf (apply pr-str* x xs))))
 
 (defn ^:private assoc!*
   "Internal implementation for `assoc!`."
   ([conf key val]
-     (conf/assoc! conf key (cc/pr-str val)))
+     (conf/assoc! conf key (pr-str* val)))
   ([conf key val & kvs]
      (let [conf (assoc!* conf key val)]
        (if (empty? kvs)

src/clojure/parkour/cser/printers.clj

@@ -0,0 +1,35 @@
+(ns parkour.cser.printers
+  (:import [java.io Writer]
+           [java.util.regex Pattern]
+           [clojure.lang Var]))
+
+(defn class-print
+  "Tagged literal printer for Java classes."
+  [^Class x ^Writer w]
+  (doto w
+    (.append "#parkour/class ")
+    (.append (.getName x))))
+
+(defn var-print
+  "Tagged literal printer for Clojure vars."
+  [^Var x ^Writer w]
+  (doto w
+    (.append "#parkour/var ")
+    (.append (str (.-ns x)))
+    (.append \/)
+    (.append (str (.-sym x)))))
+
+(defn pattern-print
+  "Tagged literal printer for Java compiled regular expressions."
+  [^Pattern x ^Writer w]
+  (doto w
+    (.append "#parkour/pattern \"")
+    (.append (str x))
+    (.append \")))
+
+(def data-printers
+  "Custom data printers for cser printing."
+  {Class class-print,
+   Var var-print,
+   Pattern pattern-print,
+   })

src/clojure/parkour/cser/readers.clj

@@ -0,0 +1,26 @@
+(ns parkour.cser.readers
+  (:import [java.util.regex Pattern]
+           [clojure.lang RT Var]))
+
+(defn class-read
+  "Tagged literal reader for Java classes."
+  [x] (Class/forName (name x) false (RT/baseLoader)))
+
+(defn var-read
+  "Tagged literal reader for Clojure vars."
+  [x]
+  (let [ns (symbol (namespace x))
+        n (symbol (name x))]
+    (require ns)
+    (intern ns n)))
+
+(defn pattern-read
+  "Tagged literal reader for Java compiled regular expressions."
+  [x] (Pattern/compile x))
+
+(def data-readers
+  "Custom data readers for cser reading."
+  {'parkour/class class-read,
+   'parkour/var var-read,
+   'parkour/pattern pattern-read,
+   })