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ConsoleReader should be blocking in sbt 1.4+ since System.in already is non-blocking #11061

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Dec 21, 2021
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ConsoleReader should be blocking in sbt 1.4+ since System.in already is non-blocking #11061

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53 changes: 39 additions & 14 deletions dev-mode/sbt-plugin/src/main/scala/play/sbt/PlayInteractionMode.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,9 @@
package play.sbt

import java.io.Closeable
import java.io.FileDescriptor
import java.io.FileInputStream
import java.io.FilterInputStream
import java.io.InputStream
import java.io.OutputStream
import jline.console.ConsoleReader
Expand Down Expand Up @@ -56,27 +59,36 @@ trait PlayNonBlockingInteractionMode extends PlayInteractionMode {
* wait on jline.
*/
object PlayConsoleInteractionMode extends PlayInteractionMode {
// This wraps the InputStream with some sleep statements so it becomes interruptible.
private[play] final class SystemInWrapper(val poll: FiniteDuration) extends InputStream {
@tailrec override def read(): Int = {
if (System.in.available() > 0) {
System.in.read()
} else {

/**
* This wraps the InputStream with some sleep statements so it becomes interruptible.
* Only used in sbt versions <= 1.3
*/
private[play] class InputStreamWrapperSbtLegacy(is: InputStream, val poll: Duration) extends FilterInputStream(is) {
@tailrec final override def read(): Int =
if (is.available() != 0) is.read()
else {
Thread.sleep(poll.toMillis)
read()
}
}

override def read(b: Array[Byte]): Int = read(b, 0, b.length)
@tailrec final override def read(b: Array[Byte]): Int =
if (is.available() != 0) is.read(b)
else {
Thread.sleep(poll.toMillis)
read(b)
}

@tailrec override def read(b: Array[Byte], off: Int, len: Int): Int = {
if (System.in.available() > 0) {
System.in.read(b, off, len)
} else {
@tailrec final override def read(b: Array[Byte], off: Int, len: Int): Int =
if (is.available() != 0) is.read(b, off, len)
else {
Thread.sleep(poll.toMillis)
read(b, off, len)
}
}
}

private[play] final class SystemInWrapper() extends InputStream {
override def read(): Int = System.in.read()
}

private[play] final class SystemOutWrapper extends OutputStream {
Expand All @@ -90,7 +102,20 @@ object PlayConsoleInteractionMode extends PlayInteractionMode {
}

private def createReader: ConsoleReader =
new ConsoleReader(new SystemInWrapper(poll = 2.milliseconds), new SystemOutWrapper())
if (System.in.getClass.getName == "java.io.BufferedInputStream") {
// sbt <= 1.3:
// In sbt <= 1.3 we need to create a non-blocking input stream reader, so sbt is able to interrupt the thread
// (e.g. when user hits Ctrl-C to cancel)
val originalIn = new FileInputStream(FileDescriptor.in)
val in = new InputStreamWrapperSbtLegacy(originalIn, 2.milliseconds)
new ConsoleReader(in, System.out)
} else {
// sbt 1.4+ (class name is "sbt.internal.util.Terminal$proxyInputStream$"):
// sbt makes System.in non-blocking starting with 1.4.0, therefore we shouldn't
// create a non-blocking input stream reader ourselves, but just wrap System.in
// and System.out (otherwise we end up in a deadlock, console will hang, not accepting inputs)
new ConsoleReader(new SystemInWrapper(), new SystemOutWrapper())
}

private def withConsoleReader[T](f: ConsoleReader => T): T = {
val consoleReader = createReader
Expand Down