.

Author: lihaoyi

runner/bsp/worker/src/mill/bsp/worker/BspWorkerImpl.scala

@@ -27,10 +27,12 @@ object BspWorkerImpl {
       noWaitForBspLock: Boolean,
       killOther: Boolean,
       bspWatch: Boolean,
-      bootstrapBridge: [T] => (
-          String,
-          (Seq[EvaluatorApi], Seq[Watchable], Option[String]) => T
-      ) => T
+      bootstrapBridge: String => (
+          Seq[EvaluatorApi],
+          Seq[Watchable],
+          Option[String],
+          AutoCloseable
+      )
   ): mill.api.Result[(BspServerHandle, BuildClient)] = {
 
     try {

runner/bsp/worker/src/mill/bsp/worker/MillBuildServer.scala

@@ -36,10 +36,12 @@ private abstract class MillBuildServer(
     noWaitForBspLock: Boolean,
     killOther: Boolean,
     bspWatch: Boolean,
-    bootstrapBridge: [T] => (
-        String,
-        (Seq[EvaluatorApi], Seq[Watchable], Option[String]) => T
-    ) => T
+    bootstrapBridge: String => (
+        Seq[EvaluatorApi],
+        Seq[Watchable],
+        Option[String],
+        AutoCloseable
+    )
 ) extends EndpointsApi with AutoCloseable {
 
   import MillBuildServer.*

runner/daemon/src/mill/daemon/BspMode.scala

@@ -10,16 +10,19 @@ import sun.misc.Signal
 import java.util.concurrent.atomic.AtomicReference
 import scala.concurrent.Await
 import scala.concurrent.duration.Duration
-import scala.util.{Failure, Success, Using}
+import scala.util.{Failure, Success}
 
 private[daemon] object BspMode {
   type RunBootstrap =
     (String, Option[RunnerLauncherState], SystemStreams, Boolean) => RunnerLauncherState
 
-  type BootstrapBridge = [T] => (
-      String,
-      (Seq[EvaluatorApi], Seq[Watchable], Option[String]) => T
-  ) => T
+  // The bridge returns the bootstrap attempt's evaluators, watched set, errorOpt,
+  // and an AutoCloseable that releases the underlying RunnerLauncherState. The
+  // caller (MillBuildServer) owns the closeable and decides whether to release it
+  // immediately (broken attempt) or retain it across requests (successful attempt
+  // serving as fallback during a future broken attempt).
+  type BootstrapBridge =
+    String => (Seq[EvaluatorApi], Seq[Watchable], Option[String], AutoCloseable)
 
   def run(
       streams: SystemStreams,
@@ -33,15 +36,12 @@ private[daemon] object BspMode {
 
     val bspPrevState = new AtomicReference[Option[RunnerLauncherState]](None)
 
-    val bootstrapBridge: BootstrapBridge = [T] =>
-      (activeCommandMessage, body) =>
-        Using.resource(
-          runMillBootstrap(activeCommandMessage, bspPrevState.get(), streams, true)
-        ) { runnerState =>
-          if (runnerState.errorOpt.isEmpty && runnerState.finalFrame.isDefined)
-            bspPrevState.set(Some(runnerState))
-          body(runnerState.allEvaluators, runnerState.watched, runnerState.errorOpt)
-      }
+    val bootstrapBridge: BootstrapBridge = activeCommandMessage => {
+      val newState = runMillBootstrap(activeCommandMessage, bspPrevState.get(), streams, true)
+      if (newState.errorOpt.isEmpty && newState.finalFrame.isDefined)
+        bspPrevState.set(Some(newState))
+      (newState.allEvaluators, newState.watched, newState.errorOpt, newState)
+    }
 
     val (bspServerHandle, _) = startBspServer(bootstrapBridge)
 

runner/daemon/src/mill/daemon/IdeWorkerSupport.scala

@@ -9,7 +9,7 @@ import mill.javalib.api.JvmWorkerUtil
 import mill.util.{BuildInfo, Jvm}
 
 private object IdeWorkerSupport {
-  case class BspBuildClient private[daemon] (private[daemon] val value: AnyRef)
+  final case class BspBuildClient private[daemon] (private[daemon] val value: AnyRef)
 
   private val organization = Organization("com.lihaoyi")
 
@@ -94,7 +94,7 @@ private object IdeWorkerSupport {
       classOf[Boolean],
       classOf[Boolean],
       classOf[Boolean],
-      classOf[scala.Function2[?, ?, ?]]
+      classOf[scala.Function1[?, ?]]
     )
 
     val bspEvaluatorsClass = classLoader.loadClass("mill.bsp.worker.BspEvaluators")