Make mill show skip -j prefixes to ensure machine readability (#2884

)

This requires us add another method `Logger#rawOutputStream`, which the
various implementations forward without decorating with prefixes or
other things.

We cannot just use `SystemStreams.original` because when running Mill in
client/server mode we still need to use the `OutputStream` that gets
forwarded from server to client, as the `SystemStreams.original.out`
just ends up forwarded to `out/mill-worker-hash-1/stdout` files that
aren't surfaced to users

Tested manually with `./mill -i dev.run tmp -i -j 2 show foo` on an
example build in the `tmp/` folder. Previously it would show the output
of `show` with a prefix e.g. `[#0] "bar"`, after this PR it shows the
output without any prefixes `"bar"`

`Logger#rawOutputStream` has to be a non-abstract method for binary
compatibility. This makes it a bit error prone since you can easily
forget to override it where necessary. So I first made it abstract, made
sure everyone overrides it, and then added the default case.

Pull request: #2884

bsp/src/mill/bsp/BspContext.scala

@@ -56,7 +56,10 @@ private[mill] class BspContext(
  override def error(s: String): Unit = streams.err.println(s)
  override def ticker(s: String): Unit = streams.err.println(s)
  override def debug(s: String): Unit = streams.err.println(s)
+
  override def debugEnabled: Boolean = true
+
+ override def rawOutputStream: PrintStream = systemStreams.out
  }
 
  BspWorker(os.pwd, home, log).flatMap { worker =>

main/api/src/mill/api/Logger.scala

@@ -31,6 +31,14 @@ trait Logger {
 
  def errorStream: PrintStream = systemStreams.err
  def outputStream: PrintStream = systemStreams.out
+
+ /**
+ * [[rawOutputStream]] is intended to be a version of [[outputStream]]
+ * without decoration: colors, prefixes, timestamps, etc. It is intended
+ * for the use of tasks like `show` which output data in a way that is
+ * easily readable by downstream programs.
+ */
+ def rawOutputStream: PrintStream = systemStreams.out
  def inStream: InputStream = systemStreams.in
 
  def info(s: String): Unit

main/eval/src/mill/eval/GroupEvaluator.scala

@@ -7,6 +7,7 @@ import mill.define._
 import mill.eval.Evaluator.TaskResult
 import mill.util._
 
+import java.io.PrintStream
 import scala.collection.mutable
 import scala.reflect.NameTransformer.{encode, decode}
 import scala.util.DynamicVariable
@@ -274,6 +275,8 @@ private[mill] trait GroupEvaluator {
  if (enableTicker) super.ticker(tickerPrefix.getOrElse("") + s)
  else () // do nothing
  }
+
+ override def rawOutputStream: PrintStream = logger.rawOutputStream
  }
  // This is used to track the usage of `T.dest` in more than one Task
  // But it's not really clear what issue we try to prevent here

main/src/mill/main/MainModule.scala

@@ -50,7 +50,7 @@ object MainModule {
  case Right((watched, Right(res))) =>
  val output = f(res)
  watched.foreach(watch0)
- log.outputStream.println(output.render(indent = 2))
+ log.rawOutputStream.println(output.render(indent = 2))
  Result.Success(output)
  }
  }

main/util/src/mill/util/DummyLogger.scala

@@ -12,6 +12,7 @@ object DummyLogger extends Logger {
  new PrintStream(_ => ()),
  new ByteArrayInputStream(Array())
  )
+ override def rawOutputStream = systemStreams.out
 
  def info(s: String) = ()
  def error(s: String) = ()

main/util/src/mill/util/FileLogger.scala

@@ -52,4 +52,6 @@ class FileLogger(
  if (outputStreamUsed)
  outputStream.close()
  }
+
+ override def rawOutputStream: PrintStream = outputStream
 }

main/util/src/mill/util/MultiLogger.scala

@@ -40,6 +40,8 @@ class MultiLogger(
  logger1.close()
  logger2.close()
  }
+
+ override def rawOutputStream: PrintStream = systemStreams.out
 }
 
 class MultiStream(stream1: OutputStream, stream2: OutputStream)

main/util/src/mill/util/PrefixLogger.scala

@@ -36,6 +36,8 @@ class PrefixLogger(
  logger0.systemStreams.in
  )
 
+ override def rawOutputStream = logger0.rawOutputStream
+
  override def info(s: String): Unit = logger0.info(context + s)
  override def error(s: String): Unit = logger0.error(context + s)
  override def ticker(s: String): Unit = logger0.ticker(context + tickerContext + s)

main/util/src/mill/util/PrintLogger.scala

@@ -76,6 +76,8 @@ class PrintLogger(
  systemStreams.err.println(context + s)
  }
  }
+
+ override def rawOutputStream: PrintStream = systemStreams.out
 }
 
 object PrintLogger {

main/util/src/mill/util/ProxyLogger.scala

@@ -2,6 +2,8 @@ package mill.util
 
 import mill.api.Logger
 
+import java.io.PrintStream
+
 /**
  * A Logger that forwards all logging to another Logger. Intended to be
  * used as a base class for wrappers that modify logging behavior.
@@ -19,4 +21,6 @@ class ProxyLogger(logger: Logger) extends Logger {
  override def debugEnabled: Boolean = logger.debugEnabled
 
  override def close() = logger.close()
+
+ override def rawOutputStream: PrintStream = logger.rawOutputStream
 }