Add support for BSP's buildTarget/outputPaths method

main/src/main/scala/sbt/Keys.scala

@@ -412,6 +412,8 @@ object Keys {
   val bspBuildTargetResourcesItem = taskKey[ResourcesItem]("").withRank(DTask)
   val bspBuildTargetDependencySources = inputKey[Unit]("").withRank(DTask)
   val bspBuildTargetDependencySourcesItem = taskKey[DependencySourcesItem]("").withRank(DTask)
+  val bspBuildTargetOutputPaths = inputKey[Unit]("").withRank(DTask)
+  val bspBuildTargetOutputPathsItem = taskKey[OutputPathsItem]("").withRank(DTask)
   val bspBuildTargetCompile = inputKey[Unit]("").withRank(DTask)
   val bspBuildTargetCompileItem = taskKey[Int]("").withRank(DTask)
   val bspBuildTargetTest = inputKey[Unit]("Corresponds to buildTarget/test request").withRank(DTask)

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

@@ -52,6 +52,7 @@ object BuildServerProtocol {
     RunProvider(BuildServerConnection.languages),
     dependencySourcesProvider = true,
     resourcesProvider = true,
+    outputPathsProvider = true,
     canReload = true,
     jvmRunEnvironmentProvider = true,
     jvmTestEnvironmentProvider = true,
@@ -158,6 +159,16 @@ object BuildServerProtocol {
       }
     }.evaluated,
     bspBuildTargetDependencySources / aggregate := false,
+    bspBuildTargetOutputPaths := bspInputTask { (state, _, workspace, filter) =>
+      Def.task {
+        import sbt.internal.bsp.codec.JsonProtocol._
+        val items = bspBuildTargetOutputPathsItem.result.all(filter).value
+        val successfulItems = anyOrThrow(items)
+        val result = OutputPathsResult(successfulItems.toVector)
+        state.respondEvent(result)
+      }
+    }.evaluated,
+    bspBuildTargetOutputPaths / aggregate := false,
     bspBuildTargetCompile := bspInputTask { (state, _, workspace, filter) =>
       workspace.warnIfBuildsNonEmpty(Method.Compile, state.log)
       Def.task {
@@ -267,6 +278,10 @@ object BuildServerProtocol {
       ResourcesItem(id, uris)
     },
     bspBuildTargetDependencySourcesItem := dependencySourcesItemTask.value,
+    bspBuildTargetOutputPathsItem := {
+      val id = bspTargetIdentifier.value
+      OutputPathsItem(id, Vector(OutputPathItem(target.value.toURI, OutputPathItemKind.Directory)))
+    },
     bspBuildTargetCompileItem := bspCompileTask.value,
     bspBuildTargetRun := bspRunTask.evaluated,
     bspBuildTargetScalacOptionsItem := scalacOptionsTask.value,
@@ -318,6 +333,7 @@ object BuildServerProtocol {
     final val Shutdown = "build/shutdown"
     final val Sources = "buildTarget/sources"
     final val Resources = "buildTarget/resources"
+    final val OutputPaths = "buildTarget/outputPaths"
     final val DependencySources = "buildTarget/dependencySources"
     final val Compile = "buildTarget/compile"
     final val Test = "buildTarget/test"
@@ -453,6 +469,12 @@ object BuildServerProtocol {
             val targets = param.targets.map(_.uri).mkString(" ")
             val command = Keys.bspBuildTargetResources.key
             val _ = callback.appendExec(s"$command $targets", Some(r.id))
+
+          case r if r.method == Method.OutputPaths =>
+            val param = Converter.fromJson[OutputPathsParams](json(r)).get
+            val targets = param.targets.map(_.uri).mkString(" ")
+            val command = Keys.bspBuildTargetOutputPaths.key
+            val _ = callback.appendExec(s"$command $targets", Some(r.id))
         },
         onResponse = PartialFunction.empty,
         onNotification = {

notes/1.8.0/bsp-output-paths.md

@@ -0,0 +1,4 @@
+[@povder]: https://github.com/povder
+
+### Improvements
+- Add support for newly introduced `buildTarget/outputPaths` method of BSP protocol. See [bsp#269](https://github.com/build-server-protocol/build-server-protocol/pull/269) pull request and [bsp#205](https://github.com/build-server-protocol/build-server-protocol/issues/205) issue.

protocol/src/main/contraband-scala/sbt/internal/bsp/BuildServerCapabilities.scala

@@ -17,6 +17,7 @@ final class BuildServerCapabilities private (
   val runProvider: Option[sbt.internal.bsp.RunProvider],
   val dependencySourcesProvider: Option[Boolean],
   val resourcesProvider: Option[Boolean],
+  val outputPathsProvider: Option[Boolean],
   val canReload: Option[Boolean],
   val jvmRunEnvironmentProvider: Option[Boolean],
   val jvmTestEnvironmentProvider: Option[Boolean]) extends Serializable {
@@ -24,17 +25,17 @@ final class BuildServerCapabilities private (
   
   
   override def equals(o: Any): Boolean = this.eq(o.asInstanceOf[AnyRef]) || (o match {
-    case x: BuildServerCapabilities => (this.compileProvider == x.compileProvider) && (this.testProvider == x.testProvider) && (this.runProvider == x.runProvider) && (this.dependencySourcesProvider == x.dependencySourcesProvider) && (this.resourcesProvider == x.resourcesProvider) && (this.canReload == x.canReload) && (this.jvmRunEnvironmentProvider == x.jvmRunEnvironmentProvider) && (this.jvmTestEnvironmentProvider == x.jvmTestEnvironmentProvider)
+    case x: BuildServerCapabilities => (this.compileProvider == x.compileProvider) && (this.testProvider == x.testProvider) && (this.runProvider == x.runProvider) && (this.dependencySourcesProvider == x.dependencySourcesProvider) && (this.resourcesProvider == x.resourcesProvider) && (this.outputPathsProvider == x.outputPathsProvider) && (this.canReload == x.canReload) && (this.jvmRunEnvironmentProvider == x.jvmRunEnvironmentProvider) && (this.jvmTestEnvironmentProvider == x.jvmTestEnvironmentProvider)
     case _ => false
   })
   override def hashCode: Int = {
-    37 * (37 * (37 * (37 * (37 * (37 * (37 * (37 * (37 * (17 + "sbt.internal.bsp.BuildServerCapabilities".##) + compileProvider.##) + testProvider.##) + runProvider.##) + dependencySourcesProvider.##) + resourcesProvider.##) + canReload.##) + jvmRunEnvironmentProvider.##) + jvmTestEnvironmentProvider.##)
+    37 * (37 * (37 * (37 * (37 * (37 * (37 * (37 * (37 * (37 * (17 + "sbt.internal.bsp.BuildServerCapabilities".##) + compileProvider.##) + testProvider.##) + runProvider.##) + dependencySourcesProvider.##) + resourcesProvider.##) + outputPathsProvider.##) + canReload.##) + jvmRunEnvironmentProvider.##) + jvmTestEnvironmentProvider.##)
   }
   override def toString: String = {
-    "BuildServerCapabilities(" + compileProvider + ", " + testProvider + ", " + runProvider + ", " + dependencySourcesProvider + ", " + resourcesProvider + ", " + canReload + ", " + jvmRunEnvironmentProvider + ", " + jvmTestEnvironmentProvider + ")"
+    "BuildServerCapabilities(" + compileProvider + ", " + testProvider + ", " + runProvider + ", " + dependencySourcesProvider + ", " + resourcesProvider + ", " + outputPathsProvider + ", " + canReload + ", " + jvmRunEnvironmentProvider + ", " + jvmTestEnvironmentProvider + ")"
   }
-  private[this] def copy(compileProvider: Option[sbt.internal.bsp.CompileProvider] = compileProvider, testProvider: Option[sbt.internal.bsp.TestProvider] = testProvider, runProvider: Option[sbt.internal.bsp.RunProvider] = runProvider, dependencySourcesProvider: Option[Boolean] = dependencySourcesProvider, resourcesProvider: Option[Boolean] = resourcesProvider, canReload: Option[Boolean] = canReload, jvmRunEnvironmentProvider: Option[Boolean] = jvmRunEnvironmentProvider, jvmTestEnvironmentProvider: Option[Boolean] = jvmTestEnvironmentProvider): BuildServerCapabilities = {
+  private[this] def copy(compileProvider: Option[sbt.internal.bsp.CompileProvider] = compileProvider, testProvider: Option[sbt.internal.bsp.TestProvider] = testProvider, runProvider: Option[sbt.internal.bsp.RunProvider] = runProvider, dependencySourcesProvider: Option[Boolean] = dependencySourcesProvider, resourcesProvider: Option[Boolean] = resourcesProvider, outputPathsProvider: Option[Boolean] = outputPathsProvider, canReload: Option[Boolean] = canReload, jvmRunEnvironmentProvider: Option[Boolean] = jvmRunEnvironmentProvider, jvmTestEnvironmentProvider: Option[Boolean] = jvmTestEnvironmentProvider): BuildServerCapabilities = {
-    new BuildServerCapabilities(compileProvider, testProvider, runProvider, dependencySourcesProvider, resourcesProvider, canReload, jvmRunEnvironmentProvider, jvmTestEnvironmentProvider)
+    new BuildServerCapabilities(compileProvider, testProvider, runProvider, dependencySourcesProvider, resourcesProvider, outputPathsProvider, canReload, jvmRunEnvironmentProvider, jvmTestEnvironmentProvider)
   }
   def withCompileProvider(compileProvider: Option[sbt.internal.bsp.CompileProvider]): BuildServerCapabilities = {
     copy(compileProvider = compileProvider)
@@ -66,6 +67,12 @@ final class BuildServerCapabilities private (
   def withResourcesProvider(resourcesProvider: Boolean): BuildServerCapabilities = {
     copy(resourcesProvider = Option(resourcesProvider))
   }
+  def withOutputPathsProvider(outputPathsProvider: Option[Boolean]): BuildServerCapabilities = {
+    copy(outputPathsProvider = outputPathsProvider)
+  }
+  def withOutputPathsProvider(outputPathsProvider: Boolean): BuildServerCapabilities = {
+    copy(outputPathsProvider = Option(outputPathsProvider))
+  }
   def withCanReload(canReload: Option[Boolean]): BuildServerCapabilities = {
     copy(canReload = canReload)
   }
@@ -87,6 +94,6 @@ final class BuildServerCapabilities private (
 }
 object BuildServerCapabilities {
   
-  def apply(compileProvider: Option[sbt.internal.bsp.CompileProvider], testProvider: Option[sbt.internal.bsp.TestProvider], runProvider: Option[sbt.internal.bsp.RunProvider], dependencySourcesProvider: Option[Boolean], resourcesProvider: Option[Boolean], canReload: Option[Boolean], jvmRunEnvironmentProvider: Option[Boolean], jvmTestEnvironmentProvider: Option[Boolean]): BuildServerCapabilities = new BuildServerCapabilities(compileProvider, testProvider, runProvider, dependencySourcesProvider, resourcesProvider, canReload, jvmRunEnvironmentProvider, jvmTestEnvironmentProvider)
+  def apply(compileProvider: Option[sbt.internal.bsp.CompileProvider], testProvider: Option[sbt.internal.bsp.TestProvider], runProvider: Option[sbt.internal.bsp.RunProvider], dependencySourcesProvider: Option[Boolean], resourcesProvider: Option[Boolean], outputPathsProvider: Option[Boolean], canReload: Option[Boolean], jvmRunEnvironmentProvider: Option[Boolean], jvmTestEnvironmentProvider: Option[Boolean]): BuildServerCapabilities = new BuildServerCapabilities(compileProvider, testProvider, runProvider, dependencySourcesProvider, resourcesProvider, outputPathsProvider, canReload, jvmRunEnvironmentProvider, jvmTestEnvironmentProvider)
-  def apply(compileProvider: sbt.internal.bsp.CompileProvider, testProvider: sbt.internal.bsp.TestProvider, runProvider: sbt.internal.bsp.RunProvider, dependencySourcesProvider: Boolean, resourcesProvider: Boolean, canReload: Boolean, jvmRunEnvironmentProvider: Boolean, jvmTestEnvironmentProvider: Boolean): BuildServerCapabilities = new BuildServerCapabilities(Option(compileProvider), Option(testProvider), Option(runProvider), Option(dependencySourcesProvider), Option(resourcesProvider), Option(canReload), Option(jvmRunEnvironmentProvider), Option(jvmTestEnvironmentProvider))
+  def apply(compileProvider: sbt.internal.bsp.CompileProvider, testProvider: sbt.internal.bsp.TestProvider, runProvider: sbt.internal.bsp.RunProvider, dependencySourcesProvider: Boolean, resourcesProvider: Boolean, outputPathsProvider: Boolean, canReload: Boolean, jvmRunEnvironmentProvider: Boolean, jvmTestEnvironmentProvider: Boolean): BuildServerCapabilities = new BuildServerCapabilities(Option(compileProvider), Option(testProvider), Option(runProvider), Option(dependencySourcesProvider), Option(resourcesProvider), Option(outputPathsProvider), Option(canReload), Option(jvmRunEnvironmentProvider), Option(jvmTestEnvironmentProvider))
 }

protocol/src/main/contraband-scala/sbt/internal/bsp/OutputPathItem.scala

@@ -0,0 +1,36 @@
+/**
+ * This code is generated using [[https://www.scala-sbt.org/contraband/ sbt-contraband]].
+ */
+
+// DO NOT EDIT MANUALLY
+package sbt.internal.bsp
+final class OutputPathItem private (
+  val uri: java.net.URI,
+  val kind: Int) extends Serializable {
+  
+  
+  
+  override def equals(o: Any): Boolean = this.eq(o.asInstanceOf[AnyRef]) || (o match {
+    case x: OutputPathItem => (this.uri == x.uri) && (this.kind == x.kind)
+    case _ => false
+  })
+  override def hashCode: Int = {
+    37 * (37 * (37 * (17 + "sbt.internal.bsp.OutputPathItem".##) + uri.##) + kind.##)
+  }
+  override def toString: String = {
+    "OutputPathItem(" + uri + ", " + kind + ")"
+  }
+  private[this] def copy(uri: java.net.URI = uri, kind: Int = kind): OutputPathItem = {
+    new OutputPathItem(uri, kind)
+  }
+  def withUri(uri: java.net.URI): OutputPathItem = {
+    copy(uri = uri)
+  }
+  def withKind(kind: Int): OutputPathItem = {
+    copy(kind = kind)
+  }
+}
+object OutputPathItem {
+  
+  def apply(uri: java.net.URI, kind: Int): OutputPathItem = new OutputPathItem(uri, kind)
+}

protocol/src/main/contraband-scala/sbt/internal/bsp/OutputPathsItem.scala

@@ -0,0 +1,36 @@
+/**
+ * This code is generated using [[https://www.scala-sbt.org/contraband/ sbt-contraband]].
+ */
+
+// DO NOT EDIT MANUALLY
+package sbt.internal.bsp
+final class OutputPathsItem private (
+  val target: sbt.internal.bsp.BuildTargetIdentifier,
+  val outputPaths: Vector[sbt.internal.bsp.OutputPathItem]) extends Serializable {
+  
+  
+  
+  override def equals(o: Any): Boolean = this.eq(o.asInstanceOf[AnyRef]) || (o match {
+    case x: OutputPathsItem => (this.target == x.target) && (this.outputPaths == x.outputPaths)
+    case _ => false
+  })
+  override def hashCode: Int = {
+    37 * (37 * (37 * (17 + "sbt.internal.bsp.OutputPathsItem".##) + target.##) + outputPaths.##)
+  }
+  override def toString: String = {
+    "OutputPathsItem(" + target + ", " + outputPaths + ")"
+  }
+  private[this] def copy(target: sbt.internal.bsp.BuildTargetIdentifier = target, outputPaths: Vector[sbt.internal.bsp.OutputPathItem] = outputPaths): OutputPathsItem = {
+    new OutputPathsItem(target, outputPaths)
+  }
+  def withTarget(target: sbt.internal.bsp.BuildTargetIdentifier): OutputPathsItem = {
+    copy(target = target)
+  }
+  def withOutputPaths(outputPaths: Vector[sbt.internal.bsp.OutputPathItem]): OutputPathsItem = {
+    copy(outputPaths = outputPaths)
+  }
+}
+object OutputPathsItem {
+  
+  def apply(target: sbt.internal.bsp.BuildTargetIdentifier, outputPaths: Vector[sbt.internal.bsp.OutputPathItem]): OutputPathsItem = new OutputPathsItem(target, outputPaths)
+}

protocol/src/main/contraband-scala/sbt/internal/bsp/OutputPathsParams.scala

@@ -0,0 +1,33 @@
+/**
+ * This code is generated using [[https://www.scala-sbt.org/contraband/ sbt-contraband]].
+ */
+
+// DO NOT EDIT MANUALLY
+package sbt.internal.bsp
+/** Build Target OutputPaths Request */
+final class OutputPathsParams private (
+  val targets: Vector[sbt.internal.bsp.BuildTargetIdentifier]) extends Serializable {
+  
+  
+  
+  override def equals(o: Any): Boolean = this.eq(o.asInstanceOf[AnyRef]) || (o match {
+    case x: OutputPathsParams => (this.targets == x.targets)
+    case _ => false
+  })
+  override def hashCode: Int = {
+    37 * (37 * (17 + "sbt.internal.bsp.OutputPathsParams".##) + targets.##)
+  }
+  override def toString: String = {
+    "OutputPathsParams(" + targets + ")"
+  }
+  private[this] def copy(targets: Vector[sbt.internal.bsp.BuildTargetIdentifier] = targets): OutputPathsParams = {
+    new OutputPathsParams(targets)
+  }
+  def withTargets(targets: Vector[sbt.internal.bsp.BuildTargetIdentifier]): OutputPathsParams = {
+    copy(targets = targets)
+  }
+}
+object OutputPathsParams {
+  
+  def apply(targets: Vector[sbt.internal.bsp.BuildTargetIdentifier]): OutputPathsParams = new OutputPathsParams(targets)
+}

protocol/src/main/contraband-scala/sbt/internal/bsp/OutputPathsResult.scala

@@ -0,0 +1,33 @@
+/**
+ * This code is generated using [[https://www.scala-sbt.org/contraband/ sbt-contraband]].
+ */
+
+// DO NOT EDIT MANUALLY
+package sbt.internal.bsp
+/** Build Target OutputPaths response */
+final class OutputPathsResult private (
+  val items: Vector[sbt.internal.bsp.OutputPathsItem]) extends Serializable {
+  
+  
+  
+  override def equals(o: Any): Boolean = this.eq(o.asInstanceOf[AnyRef]) || (o match {
+    case x: OutputPathsResult => (this.items == x.items)
+    case _ => false
+  })
+  override def hashCode: Int = {
+    37 * (37 * (17 + "sbt.internal.bsp.OutputPathsResult".##) + items.##)
+  }
+  override def toString: String = {
+    "OutputPathsResult(" + items + ")"
+  }
+  private[this] def copy(items: Vector[sbt.internal.bsp.OutputPathsItem] = items): OutputPathsResult = {
+    new OutputPathsResult(items)
+  }
+  def withItems(items: Vector[sbt.internal.bsp.OutputPathsItem]): OutputPathsResult = {
+    copy(items = items)
+  }
+}
+object OutputPathsResult {
+  
+  def apply(items: Vector[sbt.internal.bsp.OutputPathsItem]): OutputPathsResult = new OutputPathsResult(items)
+}

protocol/src/main/contraband-scala/sbt/internal/bsp/codec/BuildServerCapabilitiesFormats.scala

@@ -16,11 +16,12 @@ implicit lazy val BuildServerCapabilitiesFormat: JsonFormat[sbt.internal.bsp.Bui
       val runProvider = unbuilder.readField[Option[sbt.internal.bsp.RunProvider]]("runProvider")
       val dependencySourcesProvider = unbuilder.readField[Option[Boolean]]("dependencySourcesProvider")
       val resourcesProvider = unbuilder.readField[Option[Boolean]]("resourcesProvider")
+      val outputPathsProvider = unbuilder.readField[Option[Boolean]]("outputPathsProvider")
       val canReload = unbuilder.readField[Option[Boolean]]("canReload")
       val jvmRunEnvironmentProvider = unbuilder.readField[Option[Boolean]]("jvmRunEnvironmentProvider")
       val jvmTestEnvironmentProvider = unbuilder.readField[Option[Boolean]]("jvmTestEnvironmentProvider")
       unbuilder.endObject()
-      sbt.internal.bsp.BuildServerCapabilities(compileProvider, testProvider, runProvider, dependencySourcesProvider, resourcesProvider, canReload, jvmRunEnvironmentProvider, jvmTestEnvironmentProvider)
+      sbt.internal.bsp.BuildServerCapabilities(compileProvider, testProvider, runProvider, dependencySourcesProvider, resourcesProvider, outputPathsProvider, canReload, jvmRunEnvironmentProvider, jvmTestEnvironmentProvider)
       case None =>
       deserializationError("Expected JsObject but found None")
     }
@@ -32,6 +33,7 @@ implicit lazy val BuildServerCapabilitiesFormat: JsonFormat[sbt.internal.bsp.Bui
     builder.addField("runProvider", obj.runProvider)
     builder.addField("dependencySourcesProvider", obj.dependencySourcesProvider)
     builder.addField("resourcesProvider", obj.resourcesProvider)
+    builder.addField("outputPathsProvider", obj.outputPathsProvider)
     builder.addField("canReload", obj.canReload)
     builder.addField("jvmRunEnvironmentProvider", obj.jvmRunEnvironmentProvider)
     builder.addField("jvmTestEnvironmentProvider", obj.jvmTestEnvironmentProvider)

protocol/src/main/contraband-scala/sbt/internal/bsp/codec/ExcludeItemFormats.scala

@@ -0,0 +1,29 @@
+/**
+ * This code is generated using [[https://www.scala-sbt.org/contraband/ sbt-contraband]].
+ */
+
+// DO NOT EDIT MANUALLY
+package sbt.internal.bsp.codec
+import _root_.sjsonnew.{ Unbuilder, Builder, JsonFormat, deserializationError }
+trait ExcludeItemFormats { self: sjsonnew.BasicJsonProtocol =>
+implicit lazy val ExcludeItemFormat: JsonFormat[sbt.internal.bsp.ExcludeItem] = new JsonFormat[sbt.internal.bsp.ExcludeItem] {
+  override def read[J](__jsOpt: Option[J], unbuilder: Unbuilder[J]): sbt.internal.bsp.ExcludeItem = {
+    __jsOpt match {
+      case Some(__js) =>
+      unbuilder.beginObject(__js)
+      val uri = unbuilder.readField[java.net.URI]("uri")
+      val kind = unbuilder.readField[Int]("kind")
+      unbuilder.endObject()
+      sbt.internal.bsp.ExcludeItem(uri, kind)
+      case None =>
+      deserializationError("Expected JsObject but found None")
+    }
+  }
+  override def write[J](obj: sbt.internal.bsp.ExcludeItem, builder: Builder[J]): Unit = {
+    builder.beginObject()
+    builder.addField("uri", obj.uri)
+    builder.addField("kind", obj.kind)
+    builder.endObject()
+  }
+}
+}

protocol/src/main/contraband-scala/sbt/internal/bsp/codec/ExcludesItemFormats.scala

@@ -0,0 +1,29 @@
+/**
+ * This code is generated using [[https://www.scala-sbt.org/contraband/ sbt-contraband]].
+ */
+
+// DO NOT EDIT MANUALLY
+package sbt.internal.bsp.codec
+import _root_.sjsonnew.{ Unbuilder, Builder, JsonFormat, deserializationError }
+trait ExcludesItemFormats { self: sbt.internal.bsp.codec.BuildTargetIdentifierFormats with sbt.internal.bsp.codec.ExcludeItemFormats with sjsonnew.BasicJsonProtocol =>
+implicit lazy val ExcludesItemFormat: JsonFormat[sbt.internal.bsp.ExcludesItem] = new JsonFormat[sbt.internal.bsp.ExcludesItem] {
+  override def read[J](__jsOpt: Option[J], unbuilder: Unbuilder[J]): sbt.internal.bsp.ExcludesItem = {
+    __jsOpt match {
+      case Some(__js) =>
+      unbuilder.beginObject(__js)
+      val target = unbuilder.readField[sbt.internal.bsp.BuildTargetIdentifier]("target")
+      val excludes = unbuilder.readField[Vector[sbt.internal.bsp.ExcludeItem]]("excludes")
+      unbuilder.endObject()
+      sbt.internal.bsp.ExcludesItem(target, excludes)
+      case None =>
+      deserializationError("Expected JsObject but found None")
+    }
+  }
+  override def write[J](obj: sbt.internal.bsp.ExcludesItem, builder: Builder[J]): Unit = {
+    builder.beginObject()
+    builder.addField("target", obj.target)
+    builder.addField("excludes", obj.excludes)
+    builder.endObject()
+  }
+}
+}

protocol/src/main/contraband-scala/sbt/internal/bsp/codec/ExcludesParamsFormats.scala

@@ -0,0 +1,27 @@
+/**
+ * This code is generated using [[https://www.scala-sbt.org/contraband/ sbt-contraband]].
+ */
+
+// DO NOT EDIT MANUALLY
+package sbt.internal.bsp.codec
+import _root_.sjsonnew.{ Unbuilder, Builder, JsonFormat, deserializationError }
+trait ExcludesParamsFormats { self: sbt.internal.bsp.codec.BuildTargetIdentifierFormats with sjsonnew.BasicJsonProtocol =>
+implicit lazy val ExcludesParamsFormat: JsonFormat[sbt.internal.bsp.ExcludesParams] = new JsonFormat[sbt.internal.bsp.ExcludesParams] {
+  override def read[J](__jsOpt: Option[J], unbuilder: Unbuilder[J]): sbt.internal.bsp.ExcludesParams = {
+    __jsOpt match {
+      case Some(__js) =>
+      unbuilder.beginObject(__js)
+      val targets = unbuilder.readField[Vector[sbt.internal.bsp.BuildTargetIdentifier]]("targets")
+      unbuilder.endObject()
+      sbt.internal.bsp.ExcludesParams(targets)
+      case None =>
+      deserializationError("Expected JsObject but found None")
+    }
+  }
+  override def write[J](obj: sbt.internal.bsp.ExcludesParams, builder: Builder[J]): Unit = {
+    builder.beginObject()
+    builder.addField("targets", obj.targets)
+    builder.endObject()
+  }
+}
+}

protocol/src/main/contraband-scala/sbt/internal/bsp/codec/ExcludesResultFormats.scala

@@ -0,0 +1,27 @@
+/**
+ * This code is generated using [[https://www.scala-sbt.org/contraband/ sbt-contraband]].
+ */
+
+// DO NOT EDIT MANUALLY
+package sbt.internal.bsp.codec
+import _root_.sjsonnew.{ Unbuilder, Builder, JsonFormat, deserializationError }
+trait ExcludesResultFormats { self: sbt.internal.bsp.codec.ExcludesItemFormats with sjsonnew.BasicJsonProtocol =>
+implicit lazy val ExcludesResultFormat: JsonFormat[sbt.internal.bsp.ExcludesResult] = new JsonFormat[sbt.internal.bsp.ExcludesResult] {
+  override def read[J](__jsOpt: Option[J], unbuilder: Unbuilder[J]): sbt.internal.bsp.ExcludesResult = {
+    __jsOpt match {
+      case Some(__js) =>
+      unbuilder.beginObject(__js)
+      val items = unbuilder.readField[Vector[sbt.internal.bsp.ExcludesItem]]("items")
+      unbuilder.endObject()
+      sbt.internal.bsp.ExcludesResult(items)
+      case None =>
+      deserializationError("Expected JsObject but found None")
+    }
+  }
+  override def write[J](obj: sbt.internal.bsp.ExcludesResult, builder: Builder[J]): Unit = {
+    builder.beginObject()
+    builder.addField("items", obj.items)
+    builder.endObject()
+  }
+}
+}

protocol/src/main/contraband-scala/sbt/internal/bsp/codec/JsonProtocol.scala

@@ -29,6 +29,10 @@ trait JsonProtocol extends sjsonnew.BasicJsonProtocol
   with sbt.internal.bsp.codec.SourceItemFormats
   with sbt.internal.bsp.codec.SourcesItemFormats
   with sbt.internal.bsp.codec.SourcesResultFormats
+  with sbt.internal.bsp.codec.OutputPathsParamsFormats
+  with sbt.internal.bsp.codec.OutputPathItemFormats
+  with sbt.internal.bsp.codec.OutputPathsItemFormats
+  with sbt.internal.bsp.codec.OutputPathsResultFormats
   with sbt.internal.bsp.codec.DependencySourcesParamsFormats
   with sbt.internal.bsp.codec.DependencySourcesItemFormats
   with sbt.internal.bsp.codec.DependencySourcesResultFormats

protocol/src/main/contraband-scala/sbt/internal/bsp/codec/OutputPathItemFormats.scala

@@ -0,0 +1,29 @@
+/**
+ * This code is generated using [[https://www.scala-sbt.org/contraband/ sbt-contraband]].
+ */
+
+// DO NOT EDIT MANUALLY
+package sbt.internal.bsp.codec
+import _root_.sjsonnew.{ Unbuilder, Builder, JsonFormat, deserializationError }
+trait OutputPathItemFormats { self: sjsonnew.BasicJsonProtocol =>
+implicit lazy val OutputPathItemFormat: JsonFormat[sbt.internal.bsp.OutputPathItem] = new JsonFormat[sbt.internal.bsp.OutputPathItem] {
+  override def read[J](__jsOpt: Option[J], unbuilder: Unbuilder[J]): sbt.internal.bsp.OutputPathItem = {
+    __jsOpt match {
+      case Some(__js) =>
+      unbuilder.beginObject(__js)
+      val uri = unbuilder.readField[java.net.URI]("uri")
+      val kind = unbuilder.readField[Int]("kind")
+      unbuilder.endObject()
+      sbt.internal.bsp.OutputPathItem(uri, kind)
+      case None =>
+      deserializationError("Expected JsObject but found None")
+    }
+  }
+  override def write[J](obj: sbt.internal.bsp.OutputPathItem, builder: Builder[J]): Unit = {
+    builder.beginObject()
+    builder.addField("uri", obj.uri)
+    builder.addField("kind", obj.kind)
+    builder.endObject()
+  }
+}
+}

protocol/src/main/contraband-scala/sbt/internal/bsp/codec/OutputPathsItemFormats.scala

@@ -0,0 +1,29 @@
+/**
+ * This code is generated using [[https://www.scala-sbt.org/contraband/ sbt-contraband]].
+ */
+
+// DO NOT EDIT MANUALLY
+package sbt.internal.bsp.codec
+import _root_.sjsonnew.{ Unbuilder, Builder, JsonFormat, deserializationError }
+trait OutputPathsItemFormats { self: sbt.internal.bsp.codec.BuildTargetIdentifierFormats with sbt.internal.bsp.codec.OutputPathItemFormats with sjsonnew.BasicJsonProtocol =>
+implicit lazy val OutputPathsItemFormat: JsonFormat[sbt.internal.bsp.OutputPathsItem] = new JsonFormat[sbt.internal.bsp.OutputPathsItem] {
+  override def read[J](__jsOpt: Option[J], unbuilder: Unbuilder[J]): sbt.internal.bsp.OutputPathsItem = {
+    __jsOpt match {
+      case Some(__js) =>
+      unbuilder.beginObject(__js)
+      val target = unbuilder.readField[sbt.internal.bsp.BuildTargetIdentifier]("target")
+      val outputPaths = unbuilder.readField[Vector[sbt.internal.bsp.OutputPathItem]]("outputPaths")
+      unbuilder.endObject()
+      sbt.internal.bsp.OutputPathsItem(target, outputPaths)
+      case None =>
+      deserializationError("Expected JsObject but found None")
+    }
+  }
+  override def write[J](obj: sbt.internal.bsp.OutputPathsItem, builder: Builder[J]): Unit = {
+    builder.beginObject()
+    builder.addField("target", obj.target)
+    builder.addField("outputPaths", obj.outputPaths)
+    builder.endObject()
+  }
+}
+}

protocol/src/main/contraband-scala/sbt/internal/bsp/codec/OutputPathsParamsFormats.scala

@@ -0,0 +1,27 @@
+/**
+ * This code is generated using [[https://www.scala-sbt.org/contraband/ sbt-contraband]].
+ */
+
+// DO NOT EDIT MANUALLY
+package sbt.internal.bsp.codec
+import _root_.sjsonnew.{ Unbuilder, Builder, JsonFormat, deserializationError }
+trait OutputPathsParamsFormats { self: sbt.internal.bsp.codec.BuildTargetIdentifierFormats with sjsonnew.BasicJsonProtocol =>
+implicit lazy val OutputPathsParamsFormat: JsonFormat[sbt.internal.bsp.OutputPathsParams] = new JsonFormat[sbt.internal.bsp.OutputPathsParams] {
+  override def read[J](__jsOpt: Option[J], unbuilder: Unbuilder[J]): sbt.internal.bsp.OutputPathsParams = {
+    __jsOpt match {
+      case Some(__js) =>
+      unbuilder.beginObject(__js)
+      val targets = unbuilder.readField[Vector[sbt.internal.bsp.BuildTargetIdentifier]]("targets")
+      unbuilder.endObject()
+      sbt.internal.bsp.OutputPathsParams(targets)
+      case None =>
+      deserializationError("Expected JsObject but found None")
+    }
+  }
+  override def write[J](obj: sbt.internal.bsp.OutputPathsParams, builder: Builder[J]): Unit = {
+    builder.beginObject()
+    builder.addField("targets", obj.targets)
+    builder.endObject()
+  }
+}
+}

protocol/src/main/contraband-scala/sbt/internal/bsp/codec/OutputPathsResultFormats.scala

@@ -0,0 +1,27 @@
+/**
+ * This code is generated using [[https://www.scala-sbt.org/contraband/ sbt-contraband]].
+ */
+
+// DO NOT EDIT MANUALLY
+package sbt.internal.bsp.codec
+import _root_.sjsonnew.{ Unbuilder, Builder, JsonFormat, deserializationError }
+trait OutputPathsResultFormats { self: sbt.internal.bsp.codec.OutputPathsItemFormats with sjsonnew.BasicJsonProtocol =>
+implicit lazy val OutputPathsResultFormat: JsonFormat[sbt.internal.bsp.OutputPathsResult] = new JsonFormat[sbt.internal.bsp.OutputPathsResult] {
+  override def read[J](__jsOpt: Option[J], unbuilder: Unbuilder[J]): sbt.internal.bsp.OutputPathsResult = {
+    __jsOpt match {
+      case Some(__js) =>
+      unbuilder.beginObject(__js)
+      val items = unbuilder.readField[Vector[sbt.internal.bsp.OutputPathsItem]]("items")
+      unbuilder.endObject()
+      sbt.internal.bsp.OutputPathsResult(items)
+      case None =>
+      deserializationError("Expected JsObject but found None")
+    }
+  }
+  override def write[J](obj: sbt.internal.bsp.OutputPathsResult, builder: Builder[J]): Unit = {
+    builder.beginObject()
+    builder.addField("items", obj.items)
+    builder.endObject()
+  }
+}
+}

protocol/src/main/contraband/bsp.contra

@@ -202,6 +202,10 @@ type BuildServerCapabilities {
   # via method buildTarget/resources
   resourcesProvider: Boolean
 
+  # The server provides output paths
+  # via method buildTarget/outputPaths
+  outputPathsProvider: Boolean
+
   ## Reloading the workspace state through workspace/reload is supported
   canReload: Boolean
 
@@ -290,6 +294,26 @@ type SourceItem {
   generated: Boolean!
 }
 
+## Build Target OutputPaths Request
+type OutputPathsParams {
+  targets: [sbt.internal.bsp.BuildTargetIdentifier]
+}
+
+## Build Target OutputPaths response
+type OutputPathsResult {
+  items: [sbt.internal.bsp.OutputPathsItem]
+}
+
+type OutputPathsItem {
+  target: sbt.internal.bsp.BuildTargetIdentifier!
+  outputPaths: [sbt.internal.bsp.OutputPathItem]
+}
+
+type OutputPathItem {
+  uri: java.net.URI!
+  kind: Int!
+}
+
 ## Dependency Sources Request
 type DependencySourcesParams {
   targets: [sbt.internal.bsp.BuildTargetIdentifier]

protocol/src/main/scala/sbt/internal/bsp/BuildServerConnection.scala

@@ -17,7 +17,7 @@ import scala.util.Properties
 
 object BuildServerConnection {
   final val name = "sbt"
-  final val bspVersion = "2.0.0-M5"
+  final val bspVersion = "2.1.0-M1"
   final val languages = Vector("scala")
 
   private final val SbtLaunchJar = "sbt-launch(-.*)?\\.jar".r

protocol/src/main/scala/sbt/internal/bsp/OutputPathItemKind.scala

@@ -0,0 +1,17 @@
+/*
+ * sbt
+ * Copyright 2011 - 2018, Lightbend, Inc.
+ * Copyright 2008 - 2010, Mark Harrah
+ * Licensed under Apache License 2.0 (see LICENSE)
+ */
+
+package sbt.internal.bsp
+
+object OutputPathItemKind {
+
+  /** The output path item references a normal file.  */
+  val File: Int = 1
+
+  /** The output path item references a directory. */
+  val Directory: Int = 2
+}

server-test/src/server-test/buildserver/build.sbt

@@ -30,7 +30,9 @@ lazy val respondError = project.in(file("respond-error"))
     }
   )
 
-lazy val util = project
+lazy val util = project.settings(
+  Compile / target := baseDirectory.value / "custom-target",
+)
 
 lazy val diagnostics = project
 
@@ -44,6 +46,7 @@ lazy val badBuildTarget = project.in(file("bad-build-target"))
     Compile / bspBuildTargetDependencySourcesItem := somethingBad,
     Compile / bspBuildTargetScalacOptionsItem := somethingBad,
     Compile / bspBuildTargetCompileItem := somethingBad,
+    Compile / bspBuildTargetOutputPathsItem := somethingBad,
     Compile / bspScalaMainClasses := somethingBad,
     Test / bspBuildTarget := somethingBad,
     Test / bspScalaTestClasses := somethingBad,

server-test/src/test/scala/testpkg/BuildServerTest.scala

@@ -31,7 +31,8 @@ object BuildServerTest extends AbstractServerTest {
     initializeRequest()
     assert(svr.waitForString(10.seconds) { s =>
       (s contains """"id":"8"""") &&
-      (s contains """"resourcesProvider":true""")
+      (s contains """"resourcesProvider":true""") &&
+      (s contains """"outputPathsProvider":true""")
     })
   }
 
@@ -538,13 +539,39 @@ object BuildServerTest extends AbstractServerTest {
     })
   }
 
+  test("buildTarget/outputPaths") { _ =>
+    val buildTarget = buildTargetUri("util", "Compile")
+    val badBuildTarget = buildTargetUri("badBuildTarget", "Compile")
+    svr.sendJsonRpc(
+      s"""{ "jsonrpc": "2.0", "id": "97", "method": "buildTarget/outputPaths", "params": {
+         |  "targets": [{ "uri": "$buildTarget" }, { "uri": "$badBuildTarget" }]
+         |} }""".stripMargin
+    )
+    assert(processing("buildTarget/outputPaths"))
+    val actualResult = svr.waitFor[OutputPathsResult](10.seconds)
+    val expectedResult = OutputPathsResult(
+      items = Vector(
+        OutputPathsItem(
+          target = BuildTargetIdentifier(buildTarget),
+          outputPaths = Vector(
+            OutputPathItem(
+              uri = new File(svr.baseDirectory, "util/custom-target").toURI,
+              kind = OutputPathItemKind.Directory
+            )
+          )
+        )
+      )
+    )
+    assert(actualResult == expectedResult)
+  }
+
   private def initializeRequest(): Unit = {
     svr.sendJsonRpc(
       """{ "jsonrpc": "2.0", "id": "8", "method": "build/initialize",
         |  "params": {
         |    "displayName": "test client",
         |    "version": "1.0.0",
-        |    "bspVersion": "2.0.0-M5",
+        |    "bspVersion": "2.1.0-M1",
         |    "rootUri": "file://root/",
         |    "capabilities": { "languageIds": ["scala"] }
         |  }