refactor: split metalsLspService to main and fallback parts

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

@@ -18,12 +18,13 @@ import scala.meta.io.AbsolutePath
 
 import org.eclipse.{lsp4j => l}
 
-class BspErrorHandler(
+class ShowBspErrorHandler(
     languageClient: MetalsLanguageClient,
     workspaceFolder: AbsolutePath,
     currentSession: () => Option[BspSession],
     tables: Tables,
-)(implicit context: ExecutionContext) {
+)(implicit context: ExecutionContext)
+    extends BspErrorHandler {
 
   protected def logsPath: AbsolutePath =
     workspaceFolder.resolve(Directories.log)
@@ -53,19 +54,19 @@ class BspErrorHandler(
   protected def logError(message: String): Unit = scribe.error(message)
 
   private def showError(message: String): Future[Unit] = {
-    val bspError = s"${BspErrorHandler.errorInBsp} $message"
+    val bspError = s"${ShowBspErrorHandler.errorInBsp} $message"
     logError(bspError)
-    val params = BspErrorHandler.makeShowMessage(message)
+    val params = ShowBspErrorHandler.makeShowMessage(message)
     languageClient.showMessageRequest(params).asScala.flatMap {
-      case BspErrorHandler.goToLogs =>
+      case ShowBspErrorHandler.goToLogs =>
         val errorMsgStartLine =
           bspError.linesIterator.headOption
             .flatMap(findLine(_))
             .getOrElse(0)
         Future.successful(gotoLogs(errorMsgStartLine))
-      case BspErrorHandler.dismiss =>
+      case ShowBspErrorHandler.dismiss =>
         Future.successful(dismissedErrors.add(message)).ignoreValue
-      case BspErrorHandler.doNotShowErrors =>
+      case ShowBspErrorHandler.doNotShowErrors =>
         Future.successful {
           tables.dismissedNotifications.BspErrors.dismissForever
         }.ignoreValue
@@ -102,7 +103,7 @@ class BspErrorHandler(
   }
 }
 
-object BspErrorHandler {
+object ShowBspErrorHandler {
   def makeShowMessage(
       message: String
   ): l.ShowMessageRequestParams = {
@@ -145,3 +146,12 @@ object BspErrorHandler {
   private val MESSAGE_MAX_LENGTH = 150
 
 }
+
+trait BspErrorHandler {
+  def onError(message: String): Future[Unit]
+}
+
+object LogBspErrorHandler extends BspErrorHandler {
+  def onError(message: String): Future[Unit] =
+    Future.successful(scribe.error(message))
+}

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

@@ -57,7 +57,8 @@ final class BuildToolSelector(
   ): Future[Boolean] = {
     languageClient
       .showMessageRequest(
-        Messages.NewBuildToolDetected.params(newBuildTool, currentBuildTool)
+        Messages.NewBuildToolDetected
+          .params(newBuildTool.executableName, currentBuildTool.executableName)
       )
       .asScala
       .map {