setting query is "sbt/setting"

main/src/main/scala/sbt/internal/server/LanguageServerProtocol.scala

@@ -5,6 +5,7 @@ package server
 import sjsonnew.JsonFormat
 import sjsonnew.support.scalajson.unsafe.Converter
 import sbt.protocol.Serialization
+import sbt.protocol.{ SettingQuery => Q }
 import sbt.internal.protocol._
 import sbt.internal.protocol.codec._
 import sbt.internal.langserver._
@@ -24,6 +25,7 @@ private[sbt] trait LanguageServerProtocol extends CommandChannel {
   protected def authOptions: Set[ServerAuthentication]
   protected def setInitialized(value: Boolean): Unit
   protected def log: Logger
+  protected def onSettingQuery(execId: Option[String], req: Q): Unit
 
   protected def onRequestMessage(request: JsonRpcRequestMessage): Unit = {
 
@@ -54,6 +56,11 @@ private[sbt] trait LanguageServerProtocol extends CommandChannel {
       case "sbt/exec" =>
         val param = Converter.fromJson[SbtExecParams](json).get
         append(Exec(param.commandLine, Some(request.id), Some(CommandSource(name))))
+      case "sbt/setting" => {
+        import sbt.protocol.codec.JsonProtocol._
+        val param = Converter.fromJson[Q](json).get
+        onSettingQuery(Option(request.id), param)
+      }
       case _ => ()
     }
   }

main/src/main/scala/sbt/internal/server/NetworkChannel.scala

@@ -9,11 +9,9 @@ import java.net.{ Socket, SocketTimeoutException }
 import java.util.concurrent.atomic.AtomicBoolean
 
 import sjsonnew._
-import sjsonnew.support.scalajson.unsafe.Converter
 import scala.annotation.tailrec
 import sbt.protocol._
 import sbt.internal.langserver.ErrorCodes
-import sbt.internal.protocol.JsonRpcResponseMessage
 import sbt.internal.util.ObjectEvent
 import sbt.internal.util.codec.JValueFormats
 import sbt.util.Logger
@@ -283,7 +281,7 @@ final class NetworkChannel(val name: String,
   def onCommand(command: CommandMessage): Unit = command match {
     case x: InitCommand  => onInitCommand(x)
     case x: ExecCommand  => onExecCommand(x)
-    case x: SettingQuery => onSettingQuery(x)
+    case x: SettingQuery => onSettingQuery(None, x)
   }
 
   private def onInitCommand(cmd: InitCommand): Unit = {
@@ -312,9 +310,13 @@ final class NetworkChannel(val name: String,
     }
   }
 
-  private def onSettingQuery(req: SettingQuery) = {
+  protected def onSettingQuery(execId: Option[String], req: SettingQuery) = {
     if (initialized) {
-      StandardMain.exchange publishEventMessage SettingQuery.handleSettingQuery(req, structure)
+      import sbt.protocol.codec.JsonProtocol._
+      SettingQuery.handleSettingQueryEither(req, structure) match {
+        case Right(x) => langRespond(x, execId)
+        case Left(s)  => langError(execId, ErrorCodes.InvalidParams, s)
+      }
     } else {
       log.warn(s"ignoring query $req before initialization")
     }

main/src/main/scala/sbt/internal/server/SettingQuery.scala

@@ -110,18 +110,19 @@ object SettingQuery {
         toJson(value)
       })
 
-  def handleSettingQuery(req: SettingQuery, structure: BuildStructure): SettingQueryResponse = {
+  def handleSettingQueryEither(req: SettingQuery,
+                               structure: BuildStructure): Either[String, SettingQuerySuccess] = {
     val key = Parser.parse(req.setting, scopedKeyParser(structure))
 
-    val result =
-      for {
-        key <- key
-        json <- getSettingJsonValue(structure, key)
-      } yield SettingQuerySuccess(json, key.key.manifest.toString)
+    for {
+      key <- key
+      json <- getSettingJsonValue(structure, key)
+    } yield SettingQuerySuccess(json, key.key.manifest.toString)
+  }
 
-    result match {
+  def handleSettingQuery(req: SettingQuery, structure: BuildStructure): SettingQueryResponse =
+    handleSettingQueryEither(req, structure) match {
       case Right(x) => x
       case Left(s)  => SettingQueryFailure(s)
     }
-  }
 }

server.md

@@ -1,13 +1,34 @@
 
+$ cat ~/.sbt/1.0/server/0845deda85cb41abdb9f/token.json
+
 ### initialize
 
 ```json
 { "jsonrpc": "2.0", "id": 1, "method": "initialize", "params": { "initializationOptions": { "token": "************" } } }
 ```
 
-### ExecCommand
+### sbt/exec
 
 ```json
 { "jsonrpc": "2.0", "id": 1, "method": "sbt/exec", "params": { "commandLine": "compile" } }
 ```
 
+### sbt/setting
+
+```json
+{ "jsonrpc": "2.0", "id": 1, "method": "sbt/setting", "params": { "setting": "root/name" } }
+```
+
+Here's an example of a bad query:
+
+```json
+{ "jsonrpc": "2.0", "id": 1, "method": "sbt/setting", "params": { "setting": "name" } }
+```
+
+
+```
+Content-Length: 104
+Content-Type: application/vscode-jsonrpc; charset=utf-8
+
+{"jsonrpc":"2.0","id":"1","error":{"code":-32602,"message":"Not a valid project ID: name\nname\n    ^"}}
+```