`sbt.server.autostart` flag and startServer

Adds JVM flag `sbt.server.autostart` to enable/disable the automatic starting of sbt server with the sbt shell.

This also adds a new command `startServer` to manually start the server.

main-command/src/main/scala/sbt/BasicCommandStrings.scala

@@ -161,6 +161,12 @@ $AliasCommand name=
   def ShellDetailed =
     "Provides an interactive prompt and network server from which commands can be run."
 
+  def StartServer = "startServer"
+  def StartServerDetailed =
+    s"""$StartServer
+	Starts the server if it has not been started. This is intended to be used with
+	-Dsbt.server.autostart=false."""
+
   def OldShell = "oldshell"
   def OldShellDetailed = "Provides an interactive prompt from which commands can be run."
 

main/src/main/scala/sbt/Main.scala

@@ -195,6 +195,7 @@ object BuiltinCommands {
       multi,
       shell,
       oldshell,
+      startServer,
       BasicCommands.client,
       continuous,
       eval,
@@ -737,6 +738,12 @@ object BuiltinCommands {
     else newState.clearGlobalLog
   }
 
+  def startServer: Command =
+    Command.command(StartServer, Help.more(StartServer, StartServerDetailed)) { s0 =>
+      val exchange = StandardMain.exchange
+      exchange.runServer(s0)
+    }
+
   private val sbtVersionRegex = """sbt\.version\s*=.*""".r
   private def isSbtVersionLine(s: String) = sbtVersionRegex.pattern matcher s matches ()
 

main/src/main/scala/sbt/internal/CommandExchange.scala

@@ -23,6 +23,9 @@ import scala.util.{ Success, Failure }
  * this exchange, which could serve command request from either of the channel.
  */
 private[sbt] final class CommandExchange {
+  private val autoStartServer = sys.props.get("sbt.server.autostart") map {
+    _.toLowerCase == "true"
+  } getOrElse true
   private val lock = new AnyRef {}
   private var server: Option[ServerInstance] = None
   private var consoleChannel: Option[ConsoleChannel] = None
@@ -61,13 +64,17 @@ private[sbt] final class CommandExchange {
         consoleChannel = Some(x)
         subscribe(x)
     }
-    runServer(s)
+    if (autoStartServer) runServer(s)
+    else s
   }
 
   private def newChannelName: String = s"channel-${nextChannelId.incrementAndGet()}"
 
-  private def runServer(s: State): State = {
-    val port = (s get serverPort) match {
+  /**
+   * Check if a server instance is running already, and start one if it isn't.
+   */
+  private[sbt] def runServer(s: State): State = {
+    def port = (s get serverPort) match {
       case Some(x) => x
       case None    => 5001
     }

notes/1.0.2.markdown

@@ -11,14 +11,16 @@ This is a hotfix release for sbt 1.0.x series.
 - Fixes sbt server missing some messages. [#3523][3523] by [@guillaumebort][@guillaumebort]
 - Refixes `consoleProject`. [zinc#386][zinc386] by [@dwijnand][@dwijnand]
 - Adds JVM flag `sbt.gigahorse` to enable/disable the internal use of Gigahorse to workaround NPE in `JavaNetAuthenticator` when used in conjunction with `repositories` override. [lm#167][lm167] by [@cunei][@cunei]
+- Adds JVM flag `sbt.server.autostart` to enable/disable the automatic starting of sbt server with the sbt shell. This also adds new `startServer` command to manually start the server. by [@eed3si9n][@eed3si9n]
 
 ### Internal
 
 - Fixes unused import warnings. [#3533][3533] by [@razvan-panda][@razvan-panda]
 
-  [@dpratt]: https://github.com/dpratt
   [@dwijnand]: https://github.com/dwijnand
   [@cunei]: https://github.com/cunei
+  [@eed3si9n]: https://github.com/eed3si9n
+  [@dpratt]: https://github.com/dpratt
   [@kczulko]: https://github.com/kczulko
   [@razvan-panda]: https://github.com/razvan-panda
   [@guillaumebort]: https://github.com/guillaumebort