Support --multi-release option to create JAR manifest

Author: gavinkflam

README.md

@@ -196,6 +196,7 @@ Supported command-line options are:
 --aliases <alias:alias:...>       Colon-separated list of alias names to include from deps file. Defaults to nothing
 --target <file>                   Jar file to ouput to. Defaults to 'target/<directory-name>.jar'
 --main-class <ns>                 Main class, if it exists (e.g. app.core)
+--multi-release (true|false)      Add a multi-release flag to the manifest. Defaults to false.
 --level (debug|info|warn|error)   Verbose level. Defaults to debug
 ```
 

src/uberdeps/api.clj

@@ -111,12 +111,18 @@
 
 (defn package-manifest
   [opts out]
-  (when-some [main-class (:main-class opts)]
-    (let [manifest (str "Manifest-Version: 1.0\n"
-                     (format "Created-By: %s (%s)\n" (System/getProperty "java.version") (System/getProperty "java.vm.vendor"))
+  (let [manifest (str "Manifest-Version: 1.0\n"
+                   (format "Created-By: %s (%s)\n"
+                           (System/getProperty "java.version")
+                           (System/getProperty "java.vm.vendor"))
+                   (if-let [main-class (:main-class opts)]
                      (format "Main-Class: %s\n" main-class))
-          in       (io/input-stream (.getBytes manifest))]
-      (copy-stream in "META-INF/MANIFEST.MF" (FileTime/from (Instant/now)) out))))
+                   ; Indicate that we are generating a multi-release JAR.
+                   ; https://openjdk.java.net/jeps/238
+                   (if-let [multi-release (:multi-release opts)]
+                     (format "Multi-Release: true\n")))
+        in       (io/input-stream (.getBytes manifest))]
+    (copy-stream in "META-INF/MANIFEST.MF" (FileTime/from (Instant/now)) out)))
 
 
 (defn package-libs [deps-map out]

src/uberdeps/uberjar.clj

@@ -20,12 +20,13 @@
                      (->> (remove str/blank?)
                        (map keyword)
                        (into #{})))
-        main-class (get args "--main-class")
+        main-attrs {:main-class    (get args "--main-class")
+                    :multi-release (= (get args "--multi-release") "true")}
         level      (keyword (or (get args "--level") "debug"))]
     (binding [api/level level]
       (deps.dir/with-dir deps-dir 
         (api/package
           (edn/read-string (slurp deps-file))
           target
-          {:aliases aliases :main-class main-class})))
+          (assoc main-attrs :aliases aliases))))
     (shutdown-agents)))