Add mechanism for picking the highest java version for bloop, add docs, add fixme

Author: MaciejG604

modules/build/src/main/scala/scala/build/bsp/BspImpl.scala

@@ -620,10 +620,10 @@ final class BspImpl(
       case Right(preBuildProject) =>
         // FIXME we might want to report overridden options or chose a better merge strategy
         val projectBuildOptions = preBuildProject.prebuildModules
-          .map(_.mainScope.buildOptions)
-          .reduce(_ orElse _)
+          .flatMap(m => Seq(m.mainScope.buildOptions, m.testScope.buildOptions))
 
-        lazy val projectJavaHome = projectBuildOptions.javaHome().value
+        lazy val projectJavaHome = projectBuildOptions.map(_.javaHome().value)
+          .maxBy(_.version)
 
         val finalBloopSession =
           if (
@@ -633,10 +633,8 @@ final class BspImpl(
               s"Bloop JVM version too low, current ${bloopSession.get().remoteServer.jvmVersion.get
                   .value} expected ${projectJavaHome.version}, restarting server"
             )
-            // RelodableOptions don't take into account buildOptions from sources
+            // ReloadableOptions don't take into account buildOptions from sources, so we need to update the bloopRifleConfig
             val updatedReloadableOptions = reloadableOptions.copy(
-              buildOptions =
-                reloadableOptions.buildOptions orElse projectBuildOptions,
               bloopRifleConfig = reloadableOptions.bloopRifleConfig.copy(
                 javaPath = projectJavaHome.javaCommand,
                 minimumBloopJvm = projectJavaHome.version

modules/build/src/main/scala/scala/build/bsp/BspReloadableOptions.scala

@@ -6,6 +6,9 @@ import scala.build.Logger
 import scala.build.options.BuildOptions
 
 /** The options and configurations that may be picked up on a bsp workspace/reload request.
+  * They don't take into account options from sources.
+  * The only two exceptions are the initial options in BspImpl.run
+  * and in options used to launch new bloop in BspImpl.reloadBsp, which have the [[bloopRifleConfig]] updated.
   *
   * @param buildOptions
   *   passed options for building sources

modules/cli/src/main/scala/scala/cli/commands/bsp/Bsp.scala

@@ -137,11 +137,11 @@ object Bsp extends ScalaCommand[BspOptions] {
 
     // TODO reported override option values
     // FIXME Only some options need to be unified for the whole project, like scala version, JVM
-    val finalBuildOptions = inputsAndBuildOptions.map(_._2).reduceLeft(_ orElse _)
+    val combinedBuildOptions = inputsAndBuildOptions.map(_._2).reduceLeft(_ orElse _)
     val inputs            = inputsAndBuildOptions.map(_._1)
 
     if (options.shared.logging.verbosity >= 3)
-      pprint.err.log(finalBuildOptions)
+      pprint.err.log(combinedBuildOptions)
 
     /** values used for launching the bsp, especially for launching the bloop server, they do not
       * include options extracted from sources, except in bloopRifleConfig - it's needed for