reconnect on .bsp change

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

@@ -6,7 +6,6 @@ import scala.concurrent.ExecutionContext
 import scala.concurrent.Future
 
 import scala.meta.internal.bsp.BspConfigGenerationStatus._
-import scala.meta.internal.builds.BloopInstallProvider
 import scala.meta.internal.builds.BuildServerProvider
 import scala.meta.internal.builds.BuildTool
 import scala.meta.internal.builds.BuildTools
@@ -47,7 +46,7 @@ class BspConnector(
    */
   def resolve(buildTool: Option[BuildTool]): BspResolvedResult = {
     resolveExplicit().getOrElse {
-      if (buildTool.isInstanceOf[BloopInstallProvider] || buildTools.isBloop)
+      if (buildTool.exists(_.isBloopInstallProvider) || buildTools.isBloop)
         ResolvedBloop
       else bspServers.resolve()
     }
@@ -179,9 +178,10 @@ class BspConnector(
         possibleBuildServerConn match {
           case None => Future.successful(None)
           case Some(buildServerConn)
-              if buildServerConn.isBloop && buildTool.exists(
-                _.isInstanceOf[SbtBuildTool]
-              ) =>
+              if buildServerConn.isBloop && buildTool.exists {
+                case _: SbtBuildTool => true
+                case _ => false
+              } =>
             // NOTE: (ckipp01) we special case this here since sbt bsp server
             // doesn't yet support metabuilds. So in the future when that
             // changes, re-work this and move the creation of this out above
@@ -280,7 +280,7 @@ class BspConnector(
       if (
         bloopPresent || buildTools
           .loadSupported()
-          .exists(_.isInstanceOf[BloopInstallProvider])
+          .exists(_.isBloopInstallProvider)
       )
         new BspConnectionDetails(
           BloopServers.name,

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

@@ -9,7 +9,7 @@ import scala.meta.io.AbsolutePath
 trait BloopInstallProvider extends BuildTool {
 
   /**
-   * Method used to generate the necesary .bloop files for the
+   * Method used to generate the necessary .bloop files for the
    * build tool.
    */
   def bloopInstall(
@@ -22,4 +22,6 @@ trait BloopInstallProvider extends BuildTool {
    * Args necessary for build tool to generate the .bloop files.
    */
   def bloopInstallArgs(workspace: AbsolutePath): List[String]
+
+  override val isBloopInstallProvider = true
 }

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

@@ -1,5 +1,9 @@
 package scala.meta.internal.builds
 
+import java.security.MessageDigest
+
+import scala.meta.internal.builds.Digest
+import scala.meta.internal.mtags.MD5
 import scala.meta.io.AbsolutePath
 
 /**
@@ -9,6 +13,12 @@ case class BspOnly(
     override val executableName: String,
     override val projectRoot: AbsolutePath,
 ) extends BuildTool {
-  override def digest(workspace: AbsolutePath): Option[String] = Some("OK")
+  override def digest(workspace: AbsolutePath): Option[String] = {
+    val digest = MessageDigest.getInstance("MD5")
+    val isSuccess =
+      Digest.digestJson(workspace.resolve(s"$executableName.json"), digest)
+    if (isSuccess) Some(MD5.bytesToHex(digest.digest()))
+    else None
+  }
   override val forcesBuildServer = true
 }

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

@@ -24,6 +24,8 @@ trait BuildTool {
 
   val forcesBuildServer = false
 
+  val isBloopInstallProvider = false
+
 }
 
 object BuildTool {

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

@@ -130,16 +130,15 @@ final class BuildTools(
         .listFiles()
         .collect {
           case file
-              if file.isFile() && file.getName().endsWith(".json") && !knowBsps(
-                file.getName().stripSuffix(".json")
-              ) =>
+              if file.isFile() && file.getName().endsWith(".json") &&
+                !knownBsps(file.getName().stripSuffix(".json")) =>
             BspOnly(file.getName().stripSuffix(".json"), root)
         }
         .toList
     } else Nil
   }
 
-  private def knowBsps =
+  private def knownBsps =
     Set(SbtBuildTool.name, MillBuildTool.name) ++ ScalaCli.names
 
   private def customProjectRoot =
@@ -230,6 +229,11 @@ final class BuildTools(
       Some(MavenBuildTool.name)
     else if (isMill && MillBuildTool.isMillRelatedPath(path))
       Some(MillBuildTool.name)
+    else if (
+      path.isFile && path.filename.endsWith(".json") &&
+      path.parent.filename == ".bsp"
+    )
+      Some(path.filename.stripSuffix(".json"))
     else None
   }
 

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

@@ -4,6 +4,8 @@ import java.nio.charset.StandardCharsets
 import java.nio.file.Files
 import java.security.MessageDigest
 
+import scala.util.Success
+import scala.util.Try
 import scala.util.control.NonFatal
 import scala.xml.Comment
 import scala.xml.Node
@@ -15,6 +17,8 @@ import scala.meta.internal.mtags.MD5
 import scala.meta.internal.parsing.Trees
 import scala.meta.io.AbsolutePath
 
+import ujson.BytesRenderer
+
 case class Digest(
     md5: String,
     status: Status,
@@ -174,6 +178,19 @@ object Digest {
         false
     }
   }
+
+  def digestJson(
+      file: AbsolutePath,
+      digest: MessageDigest,
+  ): Boolean = {
+    Try(ujson.read(file.readText)) match {
+      case Success(json) =>
+        val bytes = json.transform(BytesRenderer()).toByteArray()
+        digest.update(bytes)
+        true
+      case _ => false
+    }
+  }
 }
 
 trait Digestable {

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

@@ -37,6 +37,7 @@ object Configs {
           new FileSystemWatcher(
             Either.forLeft(s"$root/project/build.properties")
           ),
+          new FileSystemWatcher(Either.forLeft(s"$root/.bsp/*.json")),
         ).asJava
       )
     }

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

@@ -19,6 +19,7 @@ import scala.meta.dialects._
 import scala.meta.inputs.Input
 import scala.meta.internal.bsp.BspSession
 import scala.meta.internal.bsp.BuildChange
+import scala.meta.internal.builds.BspOnly
 import scala.meta.internal.builds.BuildTool
 import scala.meta.internal.builds.BuildTools
 import scala.meta.internal.builds.Digest.Status
@@ -88,25 +89,33 @@ final case class Indexer(
       buildTool: BuildTool,
       checksum: String,
       importBuild: BspSession => Future[Unit],
+      reconnectToBuildServer: () => Future[BuildChange],
   ): Future[BuildChange] = {
     def reloadAndIndex(session: BspSession): Future[BuildChange] = {
       workspaceReload().persistChecksumStatus(Status.Started, buildTool)
 
-      session
-        .workspaceReload()
-        .flatMap(_ => importBuild(session))
-        .map { _ =>
-          scribe.info("Correctly reloaded workspace")
-          profiledIndexWorkspace(doctorCheck)
-          workspaceReload().persistChecksumStatus(Status.Installed, buildTool)
-          BuildChange.Reloaded
-        }
-        .recoverWith { case NonFatal(e) =>
-          scribe.error(s"Unable to reload workspace: ${e.getMessage()}")
-          workspaceReload().persistChecksumStatus(Status.Failed, buildTool)
-          languageClient.showMessage(Messages.ReloadProjectFailed)
-          Future.successful(BuildChange.Failed)
-        }
+      buildTool match {
+        case _: BspOnly => reconnectToBuildServer()
+        case _ =>
+          session
+            .workspaceReload()
+            .flatMap(_ => importBuild(session))
+            .map { _ =>
+              scribe.info("Correctly reloaded workspace")
+              profiledIndexWorkspace(doctorCheck)
+              workspaceReload().persistChecksumStatus(
+                Status.Installed,
+                buildTool,
+              )
+              BuildChange.Reloaded
+            }
+            .recoverWith { case NonFatal(e) =>
+              scribe.error(s"Unable to reload workspace: ${e.getMessage()}")
+              workspaceReload().persistChecksumStatus(Status.Failed, buildTool)
+              languageClient.showMessage(Messages.ReloadProjectFailed)
+              Future.successful(BuildChange.Failed)
+            }
+      }
     }
 
     bspSession() match {

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

@@ -2148,6 +2148,7 @@ class MetalsLspService(
           found.buildTool,
           found.digest,
           importBuild,
+          quickConnectToBuildServer,
         )
       case None =>
         Future.successful(BuildChange.None)