Add tempfile and with-tempfile to CLJS.

We already have a nice library like this for CLJ (tempfile); this builds
the same thing for CLJS, using Node.js's tmp.

package.json

@@ -13,6 +13,7 @@
     "ws": "1.1.1"
   },
   "devDependencies": {
+    "tmp": "0.0.28"
   },
   "repository": {
     "type": "git",

project.clj

@@ -41,7 +41,8 @@
               }
 
   :profiles {:dev {:dependencies [[com.cemerick/piggieback "0.2.1"]
-                                  [org.clojure/tools.nrepl "0.2.10"]]
+                                  [org.clojure/tools.nrepl "0.2.10"]
+                                  [tempfile "0.2.0"]]
                    :repl-options {:nrepl-middleware [cemerick.piggieback/wrap-cljs-repl]}
                    :plugins      [[lein-cljsbuild "1.1.2"]
                                   [lein-doo "0.1.6"]]

src/datomish/node_tempfile.cljs

@@ -0,0 +1,12 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+(ns datomish.node-tempfile
+  (:require
+   [cljs.nodejs :as nodejs]))
+
+(def tmp (nodejs/require "tmp"))
+
+(defn tempfile []
+  (.fileSync tmp)) ;; Cleaned up on process exit.

src/datomish/node_tempfile_macros.cljc

@@ -0,0 +1,18 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+(ns datomish.node-tempfile-macros)
+
+(defmacro with-tempfile
+  "Uses a tempfile for some content and delete it immediately"
+  [bindings & body]
+  (cond
+    (= (count bindings) 0) `(do ~@body)
+    (symbol? (bindings 0)) `(let ~(subvec bindings 0 2)
+                              (try
+                                (with-tempfile ~(subvec bindings 2) ~@body)
+                                (finally
+                                  (.removeCallback ~(bindings 0))))) ;; See Node.js tmp module.
+    :else (throw (java.lang.IllegalArgumentException.
+                   "with-tempfile only allows Symbols in bindings"))))