improvement: restart sbt after java home change

metals/src/main/scala/scala/meta/internal/bsp/BspConnector.scala

@@ -9,6 +9,7 @@ import scala.meta.internal.bsp.BspConfigGenerationStatus._
 import scala.meta.internal.builds.BuildServerProvider
 import scala.meta.internal.builds.BuildTools
 import scala.meta.internal.builds.SbtBuildTool
+import scala.meta.internal.builds.ShellRunner
 import scala.meta.internal.metals.BloopServers
 import scala.meta.internal.metals.BuildServerConnection
 import scala.meta.internal.metals.Messages
@@ -73,6 +74,7 @@ class BspConnector(
   def connect(
       workspace: AbsolutePath,
       userConfiguration: UserConfiguration,
+      shellRunner: ShellRunner,
   )(implicit ec: ExecutionContext): Future[Option[BspSession]] = {
     def connect(
         workspace: AbsolutePath
@@ -90,6 +92,8 @@ class BspConnector(
           val shouldReload = SbtBuildTool.writeSbtMetalsPlugins(workspace)
           val connectionF =
             for {
+              _ <- SbtBuildTool(workspace, () => userConfiguration)
+                .ensureCorrectJavaVersion(shellRunner, workspace, client)
               connection <- bspServers.newServer(workspace, details)
               _ <-
                 if (shouldReload) connection.workspaceReload()

metals/src/main/scala/scala/meta/internal/bsp/BspServers.scala

@@ -14,12 +14,14 @@ import scala.meta.internal.io.FileIO
 import scala.meta.internal.metals.BuildServerConnection
 import scala.meta.internal.metals.Cancelable
 import scala.meta.internal.metals.ClosableOutputStream
+import scala.meta.internal.metals.JdkSources
 import scala.meta.internal.metals.MetalsBuildClient
 import scala.meta.internal.metals.MetalsEnrichments._
 import scala.meta.internal.metals.MetalsServerConfig
 import scala.meta.internal.metals.QuietInputStream
 import scala.meta.internal.metals.SocketConnection
 import scala.meta.internal.metals.Tables
+import scala.meta.internal.metals.UserConfiguration
 import scala.meta.internal.metals.clients.language.MetalsLanguageClient
 import scala.meta.internal.mtags.MD5
 import scala.meta.internal.mtags.URIEncoderDecoder
@@ -43,6 +45,7 @@ final class BspServers(
     tables: Tables,
     bspGlobalInstallDirectories: List[AbsolutePath],
     config: MetalsServerConfig,
+    userConfig: () => UserConfiguration,
 )(implicit ec: ExecutionContextExecutorService) {
 
   def resolve(): BspResolvedResult = {
@@ -92,7 +95,10 @@ final class BspServers(
         args,
         projectDirectory,
         redirectErrorOutput = false,
-        Map(),
+        JdkSources
+          .defaultJavaHome(userConfig().javaHome)
+          .map("JAVA_HOME" -> _.toString())
+          .toMap,
         processOut = None,
         processErr = Some(l => scribe.info("BSP server: " + l)),
         discardInput = false,

metals/src/main/scala/scala/meta/internal/builds/SbtBuildTool.scala

@@ -4,6 +4,7 @@ import java.nio.file.Files
 import java.nio.file.Path
 import java.util.Properties
 
+import scala.concurrent.ExecutionContext
 import scala.concurrent.Future
 
 import scala.meta.inputs.Input
@@ -14,6 +15,7 @@ import scala.meta.internal.semver.SemVer.isCompatibleVersion
 import scala.meta.io.AbsolutePath
 
 import org.eclipse.lsp4j.Position
+import org.eclipse.lsp4j.services.LanguageClient
 
 case class SbtBuildTool(
     workspaceVersion: Option[String],
@@ -186,6 +188,24 @@ case class SbtBuildTool(
   override def toString: String = SbtBuildTool.name
 
   def executableName = SbtBuildTool.name
+
+  def ensureCorrectJavaVersion(
+      shellRunner: ShellRunner,
+      workspace: AbsolutePath,
+      languageClient: LanguageClient,
+  )(implicit ex: ExecutionContext): Future[Unit] =
+    if (checkCorrectJavaVersion(workspace, userConfig().javaHome)) {
+      Future.successful(())
+    } else {
+      languageClient
+        .showMessageRequest(Messages.SbtServerJavaHomeUpdate.params())
+        .asScala
+        .flatMap {
+          case Messages.SbtServerJavaHomeUpdate.restart =>
+            shutdownBspServer(shellRunner, workspace).ignoreValue
+          case _ => Future.successful(())
+        }
+    }
 }
 
 object SbtBuildTool {
@@ -382,4 +402,34 @@ object SbtBuildTool {
     val prepend = autoImports.mkString("", "\n", "\n")
     prepend + text
   }
+
+  def checkCorrectJavaVersion(
+      workspace: AbsolutePath,
+      userJavaHome: Option[String],
+  ): Boolean = {
+    val bspConfigFile = workspace.resolve(".bsp").resolve("sbt.json")
+    if (bspConfigFile.isFile) {
+      val matchesSbtJavaHome =
+        for {
+          text <- bspConfigFile.readTextOpt
+          json = ujson.read(text)
+          args <- json("argv").arrOpt
+          firstArg <- args.headOption
+          javaArg <- firstArg.strOpt
+          if (javaArg.endsWith("java"))
+        } yield {
+          val possibleJavaBinaries =
+            JavaBinary.allPossibleJavaBinaries(userJavaHome)
+          val sbtJavaHomeIsCorrect =
+            possibleJavaBinaries.exists(_.toString == javaArg)
+          if (!sbtJavaHomeIsCorrect) {
+            scribe.debug(
+              s"Java binary used by sbt server $javaArg doesn't match the expected java home. Possible paths considered: $possibleJavaBinaries"
+            )
+          }
+          sbtJavaHomeIsCorrect
+        }
+      matchesSbtJavaHome.getOrElse(true)
+    } else true
+  }
 }

metals/src/main/scala/scala/meta/internal/metals/JavaBinary.scala

@@ -39,4 +39,15 @@ object JavaBinary {
         case path if path.exists => path
       }
   }
+
+  def allPossibleJavaBinaries(
+      javaHome: Option[String]
+  ): List[AbsolutePath] = {
+    JdkSources
+      .defaultJavaHome(javaHome)
+      .flatMap(home => List(home.resolve("bin"), home.resolve("bin/jre")))
+      .flatMap(bin => List("java", "java.exe").map(bin.resolve))
+      .withFilter(_.exists)
+      .flatMap(binary => List(binary.dealias, binary))
+  }
 }

metals/src/main/scala/scala/meta/internal/metals/Messages.scala

@@ -965,4 +965,27 @@ object Messages {
     }
   }
 
+  object SbtServerJavaHomeUpdate {
+    val restart: MessageActionItem =
+      new MessageActionItem("Restart sbt server")
+
+    val notNow: MessageActionItem =
+      new MessageActionItem("Not now")
+
+    def params(): ShowMessageRequestParams = {
+      val params = new ShowMessageRequestParams()
+      params.setMessage(
+        s"Java home has been updated, do you want to restart the sbt BSP server? (the change will only be picked up after the restart)"
+      )
+      params.setType(MessageType.Info)
+      params.setActions(
+        List(
+          restart,
+          notNow,
+        ).asJava
+      )
+      params
+    }
+  }
+
 }

metals/src/main/scala/scala/meta/internal/metals/MetalsLspService.scala

@@ -411,6 +411,7 @@ class MetalsLspService(
     tables,
     bspGlobalDirectories,
     clientConfig.initialConfig,
+    userConfig,
   )
 
   private val bspConnector: BspConnector = new BspConnector(
@@ -2078,7 +2079,7 @@ class MetalsLspService(
     (for {
       _ <- disconnectOldBuildServer()
       maybeSession <- timerProvider.timed("Connected to build server", true) {
-        bspConnector.connect(folder, userConfig())
+        bspConnector.connect(folder, userConfig(), shellRunner)
       }
       result <- maybeSession match {
         case Some(session) =>