Fix a bug where the manifest is missing its last line.

Despite the documentation on java.util.jar.Manifest [1], the Manifest class
seems to require an endline in its input. If not, it drops the last line (on my
system, version [2], anyway).

[1] http://docs.oracle.com/javase/6/docs/technotes/guides/jar/jar.html
[2] $ java -version
java version "1.7.0_21"
OpenJDK Runtime Environment (IcedTea 2.3.9) (7u21-2.3.9-0ubuntu0.12.04.1)
OpenJDK 64-Bit Server VM (build 23.7-b01, mixed mode)

src/leiningen/jar.clj

@@ -28,14 +28,15 @@
         :else (str manifest "\n" (name k) ": " v)))
 
 (defn ^:internal make-manifest [project]
-  (Manifest.
-   (ByteArrayInputStream.
-    (.getBytes
-     (reduce (partial manifest-entry project)
-             "Manifest-Version: 1.0"
-             (merge default-manifest (:manifest project)
-                    (if-let [main (:main project)]
-                      {"Main-Class" (.replaceAll (str main) "-" "_")})))))))
+  (-> (reduce (partial manifest-entry project)
+              "Manifest-Version: 1.0"
+              (merge default-manifest (:manifest project)
+                     (if-let [main (:main project)]
+                       {"Main-Class" (.replaceAll (str main) "-" "_")})))
+      (str "\n")  ;; Add an endline character to make Manifest happy.
+      .getBytes
+      ByteArrayInputStream.
+      Manifest.))
 
 (defn ^:internal manifest-map [manifest]
   (let [attrs (.getMainAttributes manifest)]

test/leiningen/test/jar.clj

@@ -14,11 +14,13 @@
                    :manifest {"hello" "world"}})
 
 (deftest test-manifest
-  (is (= {"Main-Class" "foo.one_two.three_four.bar", "hello" "world"}
-         (-> mock-project
-             make-manifest
-             manifest-map
-             (select-keys ["hello" "Main-Class"])))))
+  (let [mm (-> mock-project
+               make-manifest
+               manifest-map)]
+    (is (= {"Main-Class" "foo.one_two.three_four.bar", "hello" "world"}
+           (select-keys mm ["hello" "Main-Class"])))
+    (is (= #{"Manifest-Version" "Main-Class" "hello" "Created-By" "Built-By" "Build-Jdk"}
+           (-> mm keys set)))))
 
 (deftest test-jar-fails
   (binding [*err* (java.io.PrintWriter. (platform-nullsink))]