From c80fe525c62424beb045f807ef34b02732447a16 Mon Sep 17 00:00:00 2001
From: Adrien Piquerez <adrien.piquerez@gmail.com>
Date: Thu, 14 May 2020 16:22:33 +0200
Subject: [PATCH] add BspClient

---
 .../scala/sbt/internal/client/BspClient.scala | 78 +++++++++++++++++++
 main/src/main/scala/sbt/Main.scala            | 30 ++++---
 2 files changed, 96 insertions(+), 12 deletions(-)
 create mode 100644 main-command/src/main/scala/sbt/internal/client/BspClient.scala

diff --git a/main-command/src/main/scala/sbt/internal/client/BspClient.scala b/main-command/src/main/scala/sbt/internal/client/BspClient.scala
new file mode 100644
index 000000000..22a099a9a
--- /dev/null
+++ b/main-command/src/main/scala/sbt/internal/client/BspClient.scala
@@ -0,0 +1,78 @@
+package sbt.internal.client
+
+import java.io.{ File, InputStream, OutputStream }
+import java.net.Socket
+
+import sbt.Exit
+import sbt.io.syntax._
+import sbt.protocol.ClientSocket
+
+import scala.sys.process.Process
+import scala.util.control.NonFatal
+
+class BspClient private (sbtServer: Socket) {
+
+  private def transferTo(input: InputStream, output: OutputStream): Unit = {
+    val buffer = Array.ofDim[Byte](1024)
+    while (true) {
+      val size = input.read(buffer)
+      output.write(buffer, 0, size)
+      output.flush()
+    }
+  }
+
+  private def run(): Exit = {
+    try {
+      val redirection = new Thread {
+        override def run(): Unit = transferTo(sbtServer.getInputStream, System.out)
+      }
+
+      redirection.start()
+      transferTo(System.in, sbtServer.getOutputStream)
+
+      Exit(0)
+    } catch {
+      case NonFatal(_) => Exit(1)
+    }
+  }
+}
+
+object BspClient {
+  def run(configuration: xsbti.AppConfiguration): Exit = {
+    val baseDirectory = configuration.baseDirectory
+    val portFile = baseDirectory / "project" / "target" / "active.json"
+    try {
+      if (!portFile.exists) {
+        forkServer(baseDirectory, portFile)
+      }
+      val (socket, _) = ClientSocket.socket(portFile)
+      new BspClient(socket).run()
+    } catch {
+      case NonFatal(_) => Exit(1)
+    }
+  }
+
+  /**
+   * Forks another instance of sbt in the background.
+   * This instance must be shutdown explicitly via `sbt -client shutdown`
+   */
+  def forkServer(baseDirectory: File, portfile: File): Unit = {
+    val args = List[String]()
+    val launchOpts = List("-Xms2048M", "-Xmx2048M", "-Xss2M")
+
+    val launcherJarString = sys.props.get("java.class.path") match {
+      case Some(cp) =>
+        cp.split(File.pathSeparator)
+          .headOption
+          .getOrElse(sys.error("launcher JAR classpath not found"))
+      case _ => sys.error("property java.class.path expected")
+    }
+
+    val cmd = "java" :: launchOpts ::: "-jar" :: launcherJarString :: args
+    val process = Process(cmd, baseDirectory).run()
+
+    while (process.isAlive() && !portfile.exists) Thread.sleep(100)
+
+    if (!process.isAlive()) sys.error("sbt server exited")
+  }
+}
diff --git a/main/src/main/scala/sbt/Main.scala b/main/src/main/scala/sbt/Main.scala
index 23a6e5b36..0ab32f035 100644
--- a/main/src/main/scala/sbt/Main.scala
+++ b/main/src/main/scala/sbt/Main.scala
@@ -19,6 +19,7 @@ import sbt.compiler.EvalImports
 import sbt.internal.Aggregation.AnyKeys
 import sbt.internal.CommandStrings.BootCommand
 import sbt.internal._
+import sbt.internal.client.BspClient
 import sbt.internal.inc.ScalaInstance
 import sbt.internal.nio.CheckBuildSources
 import sbt.internal.util.Types.{ const, idFun }
@@ -51,18 +52,23 @@ private[sbt] object xMain {
       val clientModByEnv = SysProp.client
       val userCommands = configuration.arguments.map(_.trim)
       val isClient: String => Boolean = cmd => (cmd == DashClient) || (cmd == DashDashClient)
-      Terminal.withStreams {
-        if (clientModByEnv || userCommands.exists(isClient)) {
-          val args = userCommands.toList.filterNot(isClient)
-          NetworkClient.run(configuration, args)
-          Exit(0)
-        } else {
-          val state = StandardMain.initialState(
-            configuration,
-            Seq(defaults, early),
-            runEarly(DefaultsCommand) :: runEarly(InitCommand) :: BootCommand :: Nil
-          )
-          StandardMain.runManaged(state)
+      val isBsp: String => Boolean = cmd => (cmd == "-bsp") || (cmd == "--bsp")
+      if (userCommands.exists(isBsp)) {
+        BspClient.run(configuration)
+      } else {
+        Terminal.withStreams {
+          if (clientModByEnv || userCommands.exists(isClient)) {
+            val args = userCommands.toList.filterNot(isClient)
+            NetworkClient.run(configuration, args)
+            Exit(0)
+          } else {
+            val state = StandardMain.initialState(
+              configuration,
+              Seq(defaults, early),
+              runEarly(DefaultsCommand) :: runEarly(InitCommand) :: BootCommand :: Nil
+            )
+            StandardMain.runManaged(state)
+          }
         }
       }
     } finally {