From 46971c03e87b0af1df2ae737ce432730b1ce4eb5 Mon Sep 17 00:00:00 2001
From: Stephen Bly <stephen.bly@bamtechmedia.com>
Date: Fri, 25 Sep 2020 15:41:36 -0400
Subject: [PATCH 1/9] WIP: Initial proguard implementation

---
 build.sc                            |  6 +++
 contrib/proguard/src/Proguard.scala | 67 +++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+)
 create mode 100644 contrib/proguard/src/Proguard.scala

diff --git a/build.sc b/build.sc
index f3b74228f75..9960e6a531d 100755
--- a/build.sc
+++ b/build.sc
@@ -75,6 +75,7 @@ object Deps {
   val zinc = ivy"org.scala-sbt::zinc:1.4.0-M1"
   val bsp = ivy"ch.epfl.scala:bsp4j:2.0.0-M4"
   val jarjarabrams = ivy"com.eed3si9n.jarjarabrams::jarjar-abrams-core:0.3.0"
+  val proguard = ivy"com.guardsquare:proguard-core:7.0.0"
 }
 
 trait MillPublishModule extends PublishModule{
@@ -454,6 +455,11 @@ object contrib extends MillModule {
     }
    }
 
+  object proguard extends MillModule {
+    override def moduleDeps = Seq(scalalib)
+    def ivyDeps = Agg(Deps.proguard, Deps.osLib)
+  }
+
   object tut extends MillModule {
     override def compileModuleDeps = Seq(scalalib)
     def testArgs = T{
diff --git a/contrib/proguard/src/Proguard.scala b/contrib/proguard/src/Proguard.scala
new file mode 100644
index 00000000000..44abfde57d4
--- /dev/null
+++ b/contrib/proguard/src/Proguard.scala
@@ -0,0 +1,67 @@
+package mill.contrib.proguard
+
+import coursier.Repositories
+import mill.T
+import mill.Agg
+import mill.api.{Logger, Loose, PathRef, Result}
+import mill.define.{Sources, Target}
+import mill.scalalib.Lib.resolveDependencies
+import mill.scalalib.{Dep, DepSyntax, Lib, ScalaModule}
+import os.proc
+import os.Path
+import os.PathChunk
+
+trait Proguard extends ScalaModule {
+  def proguardVersion: T[String] = T { "4.4" }
+
+  def shrink: T[Boolean] = T { true }
+
+  def optimize: T[Boolean] = T { true }
+
+  def obfuscate: T[Boolean] = T { true }
+
+  def preverify: T[Boolean] = T { true }
+
+  // maybe this should be the assembly() target instead?
+  def inJars: T[Seq[PathRef]] = T { localClasspath() }
+
+  def outJar: T[PathRef] = T { PathRef(T.dest / "out.jar") }
+
+  def libraryJars: T[Seq[PathRef]] = T { upstreamAssemblyClasspath().iterator.to(Seq) }
+
+  def proguard: T[PathRef] = T {
+    os
+      .proc(
+        "java -jar",
+        proguardClasspath().indexed.head.path,
+        "-injars",
+        inJars().map(_.path),
+        "-outjars",
+        outJar().path,
+        "-libraryjars",
+        libraryJars().map(_.path),
+        steps(),
+        additionalOptions()
+      )
+      .call(stdout = T.dest / "stdout.txt", stderr = T.dest / "stderr.txt")
+
+    // the call above already throws an exception on a non-zero exit code
+    outJar()
+  }
+
+  def proguardClasspath: T[Loose.Agg[PathRef]] = T {
+    resolveDependencies(
+      Seq(Repositories.central),
+      Lib.depToDependencyJava(_),
+      Seq(ivy"net.sf.proguard:proguard:${proguardVersion()}"))
+  }
+
+  def steps: T[Seq[String]] = T {
+    (if (optimize()) Seq() else Seq("-dontoptimize")) ++
+      (if (obfuscate()) Seq() else Seq("-dontobfuscate")) ++
+      (if (shrink()) Seq() else Seq("-dontshrink")) ++
+      (if (preverify()) Seq() else Seq("-dontpreverify"))
+  }
+
+  def additionalOptions: T[Seq[String]] = T { Seq[String]() }
+}

From 7302ee55bcc55efa4f59250970d53efeb1642cb6 Mon Sep 17 00:00:00 2001
From: Stephen Bly <stephen.bly@bamtechmedia.com>
Date: Fri, 25 Sep 2020 19:30:05 -0400
Subject: [PATCH 2/9] More progress: get proguard actually running

---
 contrib/proguard/src/Proguard.scala | 35 ++++++++++++++---------------
 scratch/build.sc                    |  6 ++++-
 2 files changed, 22 insertions(+), 19 deletions(-)

diff --git a/contrib/proguard/src/Proguard.scala b/contrib/proguard/src/Proguard.scala
index 44abfde57d4..f30ed5fad1e 100644
--- a/contrib/proguard/src/Proguard.scala
+++ b/contrib/proguard/src/Proguard.scala
@@ -12,30 +12,27 @@ import os.Path
 import os.PathChunk
 
 trait Proguard extends ScalaModule {
-  def proguardVersion: T[String] = T { "4.4" }
+  def proguardVersion: T[String] = T { "7.0.0" }
 
   def shrink: T[Boolean] = T { true }
-
   def optimize: T[Boolean] = T { true }
-
   def obfuscate: T[Boolean] = T { true }
-
   def preverify: T[Boolean] = T { true }
 
-  // maybe this should be the assembly() target instead?
-  def inJars: T[Seq[PathRef]] = T { localClasspath() }
-
+  def inJar: T[PathRef] = T { assembly() }
   def outJar: T[PathRef] = T { PathRef(T.dest / "out.jar") }
-
-  def libraryJars: T[Seq[PathRef]] = T { upstreamAssemblyClasspath().iterator.to(Seq) }
+  def libraryJars: T[Seq[PathRef]] = T {
+    upstreamAssemblyClasspath().toSeq
+  }
 
   def proguard: T[PathRef] = T {
-    os
-      .proc(
-        "java -jar",
-        proguardClasspath().indexed.head.path,
+    val cmd = os.proc(
+        "java",
+        "-cp",
+        proguardClasspath().map(_.path).mkString(":"),
+        "proguard.ProGuard",
         "-injars",
-        inJars().map(_.path),
+        inJar().path,
         "-outjars",
         outJar().path,
         "-libraryjars",
@@ -43,17 +40,19 @@ trait Proguard extends ScalaModule {
         steps(),
         additionalOptions()
       )
-      .call(stdout = T.dest / "stdout.txt", stderr = T.dest / "stderr.txt")
+    System.out.println("Running command: " + cmd.command.flatMap(_.value).mkString(" "))
+    cmd.call(stdout = T.dest / "stdout.txt", stderr = T.dest / "stderr.txt")
 
-    // the call above already throws an exception on a non-zero exit code
+    // the call above already throws an exception on a non-zero exit code,
+    // so if we reached this point we've succeeded!
     outJar()
   }
 
   def proguardClasspath: T[Loose.Agg[PathRef]] = T {
     resolveDependencies(
-      Seq(Repositories.central),
+      Seq(Repositories.jcenter),
       Lib.depToDependencyJava(_),
-      Seq(ivy"net.sf.proguard:proguard:${proguardVersion()}"))
+      Seq(ivy"com.guardsquare:proguard-base:${proguardVersion()}"))
   }
 
   def steps: T[Seq[String]] = T {
diff --git a/scratch/build.sc b/scratch/build.sc
index e0219632467..057fdf2d5be 100644
--- a/scratch/build.sc
+++ b/scratch/build.sc
@@ -1,6 +1,10 @@
 import mill._
 import mill.scalalib._
+//import mill.contrib.Proguard
 
-object foo extends ScalaModule{
+import $ivy.`com.lihaoyi::mill-contrib-proguard:$MILL_VERSION`
+import contrib.proguard._
+
+object foo extends ScalaModule with Proguard {
   def scalaVersion = "2.13.2"
 }
\ No newline at end of file

From 81a8b16088830fb695681bf5b15d6630dce29e5d Mon Sep 17 00:00:00 2001
From: Stephen Bly <stephen.bly@bamtechmedia.com>
Date: Mon, 5 Oct 2020 12:23:28 -0400
Subject: [PATCH 3/9] Finish proguard plugin

---
 contrib/proguard/src/Proguard.scala | 46 +++++++++++++++++++----------
 1 file changed, 31 insertions(+), 15 deletions(-)

diff --git a/contrib/proguard/src/Proguard.scala b/contrib/proguard/src/Proguard.scala
index f30ed5fad1e..6ccc91886fb 100644
--- a/contrib/proguard/src/Proguard.scala
+++ b/contrib/proguard/src/Proguard.scala
@@ -12,6 +12,9 @@ import os.Path
 import os.PathChunk
 
 trait Proguard extends ScalaModule {
+
+  // This is actually the only available version on Maven currently.
+  // But we should keep it as a configuration in case a new version is released.
   def proguardVersion: T[String] = T { "7.0.0" }
 
   def shrink: T[Boolean] = T { true }
@@ -19,28 +22,34 @@ trait Proguard extends ScalaModule {
   def obfuscate: T[Boolean] = T { true }
   def preverify: T[Boolean] = T { true }
 
+  def javaHome: T[PathRef] = T {
+    PathRef(Path(System.getProperty("java.home")))
+  }
+
   def inJar: T[PathRef] = T { assembly() }
   def outJar: T[PathRef] = T { PathRef(T.dest / "out.jar") }
   def libraryJars: T[Seq[PathRef]] = T {
-    upstreamAssemblyClasspath().toSeq
+    val javaJars = os.list(javaHome().path / "lib", sort = false).filter(_.ext == "jar")
+    javaJars.toSeq.map(PathRef(_))
   }
 
   def proguard: T[PathRef] = T {
     val cmd = os.proc(
-        "java",
-        "-cp",
-        proguardClasspath().map(_.path).mkString(":"),
-        "proguard.ProGuard",
-        "-injars",
-        inJar().path,
-        "-outjars",
-        outJar().path,
-        "-libraryjars",
-        libraryJars().map(_.path),
-        steps(),
-        additionalOptions()
-      )
-    System.out.println("Running command: " + cmd.command.flatMap(_.value).mkString(" "))
+      "java",
+      "-cp",
+      proguardClasspath().map(_.path).mkString(":"),
+      "proguard.ProGuard",
+      steps(),
+      "-injars",
+      inJar().path,
+      "-outjars",
+      outJar().path,
+      "-libraryjars",
+      libraryJars().map(_.path).mkString(":"),
+      entryPoint(),
+      additionalOptions()
+    )
+    System.out.println(cmd.command.flatMap(_.value).mkString(" "))
     cmd.call(stdout = T.dest / "stdout.txt", stderr = T.dest / "stderr.txt")
 
     // the call above already throws an exception on a non-zero exit code,
@@ -62,5 +71,12 @@ trait Proguard extends ScalaModule {
       (if (preverify()) Seq() else Seq("-dontpreverify"))
   }
 
+  def entryPoint: T[String] = T {
+    s"""|-keep public class ${finalMainClass()} {
+        |    public static void main(java.lang.String[]);
+        |}
+        |""".stripMargin
+  }
+
   def additionalOptions: T[Seq[String]] = T { Seq[String]() }
 }

From 5bf236bf255a2014fe79ea3d7270c17bded421fb Mon Sep 17 00:00:00 2001
From: Stephen Bly <stephen.bly@bamtechmedia.com>
Date: Mon, 5 Oct 2020 12:26:40 -0400
Subject: [PATCH 4/9] Reset file

---
 scratch/build.sc | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/scratch/build.sc b/scratch/build.sc
index 057fdf2d5be..e0219632467 100644
--- a/scratch/build.sc
+++ b/scratch/build.sc
@@ -1,10 +1,6 @@
 import mill._
 import mill.scalalib._
-//import mill.contrib.Proguard
 
-import $ivy.`com.lihaoyi::mill-contrib-proguard:$MILL_VERSION`
-import contrib.proguard._
-
-object foo extends ScalaModule with Proguard {
+object foo extends ScalaModule{
   def scalaVersion = "2.13.2"
 }
\ No newline at end of file

From 562c3c44e1f0892a1c29cb1286533c3d2f5ef5e2 Mon Sep 17 00:00:00 2001
From: Stephen Bly <stephen.bly@bamtechmedia.com>
Date: Tue, 6 Oct 2020 12:55:14 -0400
Subject: [PATCH 5/9] PR feedback

---
 build.sc                            | 4 +---
 contrib/proguard/src/Proguard.scala | 6 ++++--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/build.sc b/build.sc
index 9960e6a531d..377579c7b91 100755
--- a/build.sc
+++ b/build.sc
@@ -75,7 +75,6 @@ object Deps {
   val zinc = ivy"org.scala-sbt::zinc:1.4.0-M1"
   val bsp = ivy"ch.epfl.scala:bsp4j:2.0.0-M4"
   val jarjarabrams = ivy"com.eed3si9n.jarjarabrams::jarjar-abrams-core:0.3.0"
-  val proguard = ivy"com.guardsquare:proguard-core:7.0.0"
 }
 
 trait MillPublishModule extends PublishModule{
@@ -456,8 +455,7 @@ object contrib extends MillModule {
    }
 
   object proguard extends MillModule {
-    override def moduleDeps = Seq(scalalib)
-    def ivyDeps = Agg(Deps.proguard, Deps.osLib)
+    override def compileModuleDeps = Seq(scalalib)
   }
 
   object tut extends MillModule {
diff --git a/contrib/proguard/src/Proguard.scala b/contrib/proguard/src/Proguard.scala
index 6ccc91886fb..bfecb330c0e 100644
--- a/contrib/proguard/src/Proguard.scala
+++ b/contrib/proguard/src/Proguard.scala
@@ -27,13 +27,15 @@ trait Proguard extends ScalaModule {
   }
 
   def inJar: T[PathRef] = T { assembly() }
-  def outJar: T[PathRef] = T { PathRef(T.dest / "out.jar") }
+
   def libraryJars: T[Seq[PathRef]] = T {
     val javaJars = os.list(javaHome().path / "lib", sort = false).filter(_.ext == "jar")
     javaJars.toSeq.map(PathRef(_))
   }
 
   def proguard: T[PathRef] = T {
+    val outJar = PathRef(T.dest / "out.jar")
+
     val cmd = os.proc(
       "java",
       "-cp",
@@ -54,7 +56,7 @@ trait Proguard extends ScalaModule {
 
     // the call above already throws an exception on a non-zero exit code,
     // so if we reached this point we've succeeded!
-    outJar()
+    outJar
   }
 
   def proguardClasspath: T[Loose.Agg[PathRef]] = T {

From 6d0804a431fa4098b6e8def88f8b7e1656fe9347 Mon Sep 17 00:00:00 2001
From: Stephen Bly <stephen.bly@bamtechmedia.com>
Date: Wed, 7 Oct 2020 12:25:23 -0400
Subject: [PATCH 6/9] Add documentation; use Java home binary

---
 contrib/proguard/src/Proguard.scala |  5 +++--
 docs/pages/9 - Contrib Modules.md   | 32 +++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/contrib/proguard/src/Proguard.scala b/contrib/proguard/src/Proguard.scala
index bfecb330c0e..5513c32a2c4 100644
--- a/contrib/proguard/src/Proguard.scala
+++ b/contrib/proguard/src/Proguard.scala
@@ -35,9 +35,10 @@ trait Proguard extends ScalaModule {
 
   def proguard: T[PathRef] = T {
     val outJar = PathRef(T.dest / "out.jar")
+    val java = javaHome().path / "bin" / "java"
 
     val cmd = os.proc(
-      "java",
+      java,
       "-cp",
       proguardClasspath().map(_.path).mkString(":"),
       "proguard.ProGuard",
@@ -45,7 +46,7 @@ trait Proguard extends ScalaModule {
       "-injars",
       inJar().path,
       "-outjars",
-      outJar().path,
+      outJar.path,
       "-libraryjars",
       libraryJars().map(_.path).mkString(":"),
       entryPoint(),
diff --git a/docs/pages/9 - Contrib Modules.md b/docs/pages/9 - Contrib Modules.md
index 80fea16e8c9..74c1e2e045b 100644
--- a/docs/pages/9 - Contrib Modules.md	
+++ b/docs/pages/9 - Contrib Modules.md	
@@ -622,6 +622,38 @@ object app extends ScalaModule with RouterModule {
 }
 ```
 
+## Proguard
+
+This module allows [Proguard](https://www.guardsquare.com/en/products/proguard/manual/introduction) to be used in Mill builds.
+ProGuard is a Java class file shrinker, optimizer, obfuscator, and preverifier. 
+
+By default, all four steps - shrink, optimize, obfuscate, verify - are run, but this can be configured through task options.
+Any additional options can be specified as a list of strings with `additionalOptions`. The full list of proguard options
+can be found [here](https://www.guardsquare.com/en/products/proguard/manual/usage).
+
+The output of `assembly` is used as the input jar and the output is written to `out.jar` in the `dest` folder.
+
+The `stdout` and `stderr` from the proguard command can be found under the `dest` folder.
+
+The only default entrypoint is the main class (i.e. `finalMainClass` task). Additional entrypoints can be configured using `additionalOptions` as well.
+
+Here is a simple example:
+
+```
+import $ivy.`com.lihaoyi::mill-contrib-proguard:$MILL_VERSION`
+import contrib.proguard._
+
+object foo extends ScalaModule with Proguard {
+  def scalaVersion = "2.12.0"
+
+  override def shrink: T[Boolean] = T { true }
+  override def optimize: T[Boolean] = T { false }
+  override def obfuscate: T[Boolean] = T { false }
+}
+```
+
+Also, please note that Proguard doesn't seem to work with scala 2.13 yet.
+
 ## ScalaPB
 
 This module allows [ScalaPB](https://scalapb.github.io) to be used in Mill builds. ScalaPB is a [Protocol Buffers](https://developers.google.com/protocol-buffers/) compiler plugin that generates Scala case classes, encoders and decoders for protobuf messages.

From 22accede0408ffaa3c04123b86d92553f01ab62e Mon Sep 17 00:00:00 2001
From: Stephen Bly <stephen.bly@bamtechmedia.com>
Date: Thu, 8 Oct 2020 14:09:59 -0400
Subject: [PATCH 7/9] Add ScalaDoc

---
 contrib/proguard/src/Proguard.scala | 50 +++++++++++++++++++++++++++--
 1 file changed, 47 insertions(+), 3 deletions(-)

diff --git a/contrib/proguard/src/Proguard.scala b/contrib/proguard/src/Proguard.scala
index 5513c32a2c4..6db579af3b3 100644
--- a/contrib/proguard/src/Proguard.scala
+++ b/contrib/proguard/src/Proguard.scala
@@ -11,28 +11,60 @@ import os.proc
 import os.Path
 import os.PathChunk
 
+/** Adds proguard capabilities when mixed-in to a module
+ *
+ * The target name is `proguard`. This runs proguard on the output jar of `asssembly`
+ * and outputs a shrunk/obfuscated/optimized jar under `out.jar` in the `dest/` folder.
+ *
+ * Sensible defaults are provided, so no members require overriding..
+ *
+ */
 trait Proguard extends ScalaModule {
 
-  // This is actually the only available version on Maven currently.
-  // But we should keep it as a configuration in case a new version is released.
+  /** The version of proguard to download from Maven.
+   *
+   * Note that currently this is the only available version. */
   def proguardVersion: T[String] = T { "7.0.0" }
 
+  /** Run the "shrink" step in the proguard pipeline. Defaults to true. */
   def shrink: T[Boolean] = T { true }
+
+  /** Run the "optimize" step in the proguard pipeline. Defaults to true. */
   def optimize: T[Boolean] = T { true }
+
+  /** Run the "obfuscate" step in the proguard pipeline. Defaults to true. */
   def obfuscate: T[Boolean] = T { true }
+
+  /** Run the "optimize" step in the proguard pipeline. Defaults to true.
+   *
+   * Note that this is required for Java 7 and above.
+   */
   def preverify: T[Boolean] = T { true }
 
+  /** The path to JAVA_HOME.
+   *
+   * This is used for both the `java` command binary,
+   * as well as the standard library jars.
+   * Defaults to the `java.home` system property. */
   def javaHome: T[PathRef] = T {
     PathRef(Path(System.getProperty("java.home")))
   }
 
+  /** Specifies the input jar to proguard. Defaults to the output of the `assembly` task. */ */
   def inJar: T[PathRef] = T { assembly() }
 
+  /** The library jars proguard requires
+   * Defaults the jars under `javaHome`. */
   def libraryJars: T[Seq[PathRef]] = T {
     val javaJars = os.list(javaHome().path / "lib", sort = false).filter(_.ext == "jar")
     javaJars.toSeq.map(PathRef(_))
   }
 
+  /** Run the proguard task.
+   *
+   *  The full command will be printed when run.
+   *  The stdout and stderr of the command are written to the `dest/` folder.
+   *  The output jar is written to `dest/our.jar`. */
   def proguard: T[PathRef] = T {
     val outJar = PathRef(T.dest / "out.jar")
     val java = javaHome().path / "bin" / "java"
@@ -60,6 +92,9 @@ trait Proguard extends ScalaModule {
     outJar
   }
 
+  /** The location of the proguard jar files.
+   * These are downloaded from JCenter and fed to `java -cp`
+   */
   def proguardClasspath: T[Loose.Agg[PathRef]] = T {
     resolveDependencies(
       Seq(Repositories.jcenter),
@@ -67,13 +102,18 @@ trait Proguard extends ScalaModule {
       Seq(ivy"com.guardsquare:proguard-base:${proguardVersion()}"))
   }
 
-  def steps: T[Seq[String]] = T {
+  private def steps: T[Seq[String]] = T {
     (if (optimize()) Seq() else Seq("-dontoptimize")) ++
       (if (obfuscate()) Seq() else Seq("-dontobfuscate")) ++
       (if (shrink()) Seq() else Seq("-dontshrink")) ++
       (if (preverify()) Seq() else Seq("-dontpreverify"))
   }
 
+  /** The default `entrypoint` to proguard.
+   *
+   * Defaults to the `main` method of `finalMainClass`.
+   * Can be overriden to specify a different entrypoint,
+   * or additional entrypoints can be specified with `additionalOptions`. */
   def entryPoint: T[String] = T {
     s"""|-keep public class ${finalMainClass()} {
         |    public static void main(java.lang.String[]);
@@ -81,5 +121,9 @@ trait Proguard extends ScalaModule {
         |""".stripMargin
   }
 
+  /** Specify any additional options to proguard.
+   *
+   * These are fed as-is to the proguard command.
+   * */
   def additionalOptions: T[Seq[String]] = T { Seq[String]() }
 }

From a901fbd852ea73a6b85a26bcec47892502d4eade Mon Sep 17 00:00:00 2001
From: Stephen Bly <stephen.bly@bamtechmedia.com>
Date: Fri, 9 Oct 2020 10:24:54 -0400
Subject: [PATCH 8/9] PR feedback

---
 contrib/proguard/src/Proguard.scala | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/contrib/proguard/src/Proguard.scala b/contrib/proguard/src/Proguard.scala
index 6db579af3b3..8f02f8d6fea 100644
--- a/contrib/proguard/src/Proguard.scala
+++ b/contrib/proguard/src/Proguard.scala
@@ -46,7 +46,7 @@ trait Proguard extends ScalaModule {
    * This is used for both the `java` command binary,
    * as well as the standard library jars.
    * Defaults to the `java.home` system property. */
-  def javaHome: T[PathRef] = T {
+  def javaHome: T[PathRef] = T.input {
     PathRef(Path(System.getProperty("java.home")))
   }
 
@@ -66,7 +66,7 @@ trait Proguard extends ScalaModule {
    *  The stdout and stderr of the command are written to the `dest/` folder.
    *  The output jar is written to `dest/our.jar`. */
   def proguard: T[PathRef] = T {
-    val outJar = PathRef(T.dest / "out.jar")
+    val outJar = T.dest / "out.jar"
     val java = javaHome().path / "bin" / "java"
 
     val cmd = os.proc(
@@ -78,7 +78,7 @@ trait Proguard extends ScalaModule {
       "-injars",
       inJar().path,
       "-outjars",
-      outJar.path,
+      outJar,
       "-libraryjars",
       libraryJars().map(_.path).mkString(":"),
       entryPoint(),
@@ -89,7 +89,7 @@ trait Proguard extends ScalaModule {
 
     // the call above already throws an exception on a non-zero exit code,
     // so if we reached this point we've succeeded!
-    outJar
+    PathRef(outJar)
   }
 
   /** The location of the proguard jar files.

From 04ceab75c4176d57db78537932e7b61fccca823d Mon Sep 17 00:00:00 2001
From: Stephen Bly <stephen.bly@bamtechmedia.com>
Date: Fri, 30 Oct 2020 16:34:35 -0400
Subject: [PATCH 9/9] Add some basic tests

---
 contrib/proguard/src/Proguard.scala           |  2 +-
 .../test/resources/proguard/src/Main.scala    |  5 ++
 contrib/proguard/test/src/ProguardTests.scala | 50 +++++++++++++++++++
 3 files changed, 56 insertions(+), 1 deletion(-)
 create mode 100644 contrib/proguard/test/resources/proguard/src/Main.scala
 create mode 100644 contrib/proguard/test/src/ProguardTests.scala

diff --git a/contrib/proguard/src/Proguard.scala b/contrib/proguard/src/Proguard.scala
index 8f02f8d6fea..4ad1ff34399 100644
--- a/contrib/proguard/src/Proguard.scala
+++ b/contrib/proguard/src/Proguard.scala
@@ -50,7 +50,7 @@ trait Proguard extends ScalaModule {
     PathRef(Path(System.getProperty("java.home")))
   }
 
-  /** Specifies the input jar to proguard. Defaults to the output of the `assembly` task. */ */
+  /** Specifies the input jar to proguard. Defaults to the output of the `assembly` task. */
   def inJar: T[PathRef] = T { assembly() }
 
   /** The library jars proguard requires
diff --git a/contrib/proguard/test/resources/proguard/src/Main.scala b/contrib/proguard/test/resources/proguard/src/Main.scala
new file mode 100644
index 00000000000..d435838289d
--- /dev/null
+++ b/contrib/proguard/test/resources/proguard/src/Main.scala
@@ -0,0 +1,5 @@
+import java.nio.file.{Files, Paths}
+
+object Main extends App {
+
+}
diff --git a/contrib/proguard/test/src/ProguardTests.scala b/contrib/proguard/test/src/ProguardTests.scala
new file mode 100644
index 00000000000..2cac1096dcd
--- /dev/null
+++ b/contrib/proguard/test/src/ProguardTests.scala
@@ -0,0 +1,50 @@
+package mill.contrib.proguard
+
+import mill._
+import mill.define.Sources
+import mill.define.Target
+import mill.scalalib.ScalaModule
+import mill.util.TestEvaluator
+import mill.util.TestUtil
+import os.Path
+import utest._
+import utest.framework.TestPath
+
+object ProguardTests extends TestSuite {
+
+  object Proguard
+    extends TestUtil.BaseModule
+      with scalalib.ScalaModule
+      with Proguard {
+    // override build root to test custom builds/modules
+    override def millSourcePath: Path = TestUtil.getSrcPathStatic()
+    override def scalaVersion = "2.12.0"
+  }
+
+  val testModuleSourcesPath: Path = os.pwd / 'contrib / 'proguard / 'test / 'resources / "proguard"
+
+  def workspaceTest[T](m: TestUtil.BaseModule)(t: TestEvaluator => T)(
+    implicit tp: TestPath): T = {
+    val eval = new TestEvaluator(m)
+    os.remove.all(m.millSourcePath)
+    os.remove.all(eval.outPath)
+    os.makeDir.all(m.millSourcePath / os.up)
+    os.copy(testModuleSourcesPath, m.millSourcePath)
+    t(eval)
+  }
+
+  def tests: Tests = Tests {
+    'proguard - {
+      "should download proguard jars" - workspaceTest(Proguard) { eval =>
+        val Right((agg, _)) = eval.apply(Proguard.proguardClasspath)
+        assert(!agg.isEmpty)
+      }
+
+      "create proguarded jar" - workspaceTest(Proguard) { eval =>
+        val Right((path, _)) = eval.apply(Proguard.proguard)
+        assert(os.exists(path.path))
+      }
+
+    }
+  }
+}