如何配置SBT在给定某些系统属性时跳过proguard任务。

我正在使用sbt、sbt native packager和sbt proguard为3种环境制作软件包，如开发、登台和生产环境。我想做的是能够指定是否使用proguard制作包。例如，以下命令使用proguard生成包：

$ sbt -Dforceobfuscate=true -Denv=dev rpm:pakageBin

但是下面的命令使包不带proguard

$ sbt -Denv=dev rpm:packageBin

我试了两次。一个是根据系统属性条件重写任务，另一个是使用动态任务重写任务

def obfuscateOrNot = Def.taskDyn {
  if (sys.props.get("forceobfuscate").isDefined) {
    Def.task {
      ( ProguardKeys.proguard in Proguard ).value
    }
  } else { 
    Def.task {
      Seq(new File("dummy")) 
    }
  }
}

ProguardKeys.proguard in Proguard := { 
  obfuscateOrNot.value
}

1.仅通过系统属性覆盖任务

ProguardKeys.proguard in Proguard := { 
  if (sys.props.get("forceobfuscate").isDefined) {
    ( ProguardKeys.proguard in Proguard ).value
  } else {
    Seq(new File("dummy")) 
  }
}

此设置始终运行proguard任务（我不知道为什么）。 我还尝试了以下设置，以确保覆盖任务可以停止任务

ProguardKeys.proguard in Proguard := { 
  if (sys.props.get("forceobfuscate").isDefined) {
    // ( ProguardKeys.proguard in Proguard ).value
    Seq(new File("dummy")) 
  } else {
    Seq(new File("dummy")) 
  }
}

实际上，上述设置总是跳过proguard任务

2.使用动态任务覆盖任务

def obfuscateOrNot = Def.taskDyn {
  if (sys.props.get("forceobfuscate").isDefined) {
    Def.task {
      ( ProguardKeys.proguard in Proguard ).value
    }
  } else { 
    Def.task {
      Seq(new File("dummy")) 
    }
  }
}

ProguardKeys.proguard in Proguard := { 
  obfuscateOrNot.value
}

然后运行命令：

$ sbt rpm:packageBin

$ sbt -Dforceobfuscate=true rpm:packageBin

好的，这次跳过proguard任务。但当我运行命令时：

$ sbt rpm:packageBin

$ sbt -Dforceobfuscate=true rpm:packageBin

我得到了以下错误：

sbt.Init$RuntimeUndefined: References to undefined settings at runtime.
sbt.Init$RuntimeUndefined: References to undefined settings at runtime.
setting(ScopedKey(Scope(Select(ProjectRef(file:/work/backend/,backend)),Select(ConfigKey(proguard)),Global,Global),proguard)) at RangePosition(/work/backend/build.sbt,LineRange(244,247)) referenced from ScopedKey(Scope(Select(ProjectRef(file:/work/backend/,backend)),Select(ConfigKey(proguard)),Global,Global),proguard)
    at sbt.Init$class.sbt$Init$$handleUndefined(Settings.scala:511)
    at sbt.Init$$anon$4.apply(Settings.scala:516)
    at sbt.Init$$anon$4.apply(Settings.scala:516)
    at sbt.$tilde$greater$$anon$6.apply(TypeFunctions.scala:39)
    at sbt.$tilde$greater$$anon$6.apply(TypeFunctions.scala:39)
    at sbt.std.FullInstance$$anonfun$flatten$1$$anonfun$apply$3.apply(TaskMacro.scala:51)
    at sbt.std.FullInstance$$anonfun$flatten$1$$anonfun$apply$3.apply(TaskMacro.scala:51)
    at scala.Function1$$anonfun$compose$1.apply(Function1.scala:47)
    at sbt.$tilde$greater$$anonfun$$u2219$1.apply(TypeFunctions.scala:40)
    at sbt.std.Transform$$anon$4.work(System.scala:63)
    at sbt.Execute$$anonfun$submit$1$$anonfun$apply$1.apply(Execute.scala:228)
    at sbt.Execute$$anonfun$submit$1$$anonfun$apply$1.apply(Execute.scala:228)
    at sbt.ErrorHandling$.wideConvert(ErrorHandling.scala:17)
    at sbt.Execute.work(Execute.scala:237)
    at sbt.Execute$$anonfun$submit$1.apply(Execute.scala:228)
    at sbt.Execute$$anonfun$submit$1.apply(Execute.scala:228)
    at sbt.ConcurrentRestrictions$$anon$4$$anonfun$1.apply(ConcurrentRestrictions.scala:159)
    at sbt.CompletionService$$anon$2.call(CompletionService.scala:28)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
[error] (proguard:proguard) sbt.Init$RuntimeUndefined: References to undefined settings at runtime.
[error] setting(ScopedKey(Scope(Select(ProjectRef(file:/work/backend/,backend)),Select(ConfigKey(proguard)),Global,Global),proguard)) at RangePosition(/work/backend/build.sbt,LineRange(244,247)) referenced from ScopedKey(Scope(Select(ProjectRef(file:/work/backend/,backend)),Select(ConfigKey(proguard)),Global,Global),proguard)
[error] Total time: 1 s, completed 2017/07/29 12:09:24

我认为错误表明proguard没有设置，但我不确定如何使用DynamicTask设置

---

我想使上述命令工作良好。任何解决方案都可以。

我找到了一个解决方案。解决方案是根据条件设置proguard

Seq[Setting[\u]]

值

lazy val customProguardSettings = 
  if (sys.props.get("forceobfuscate").isDefined) {
    proguardSettings ++ Seq( ... )
  } else {
    Nil
  }

customProguardSettings