bugfix: Never set empty Scala JS version from sbt

PReviously, we were always expecting scala JS plugin to find the correct version of Scala JS, however I think for Scala 3 it's not a plugin, which is causing the version field to be empty. Now, we look for the scala-js library instead and default to the latest known scala js version.

build.sbt

@@ -336,6 +336,7 @@ val integrations = file("integrations")
 lazy val sbtBloop: Project = project
   .enablePlugins(ScriptedPlugin)
   .disablePlugins(ScalafixPlugin)
+  .enablePlugins(BuildInfoPlugin)
   .in(integrations / "sbt-bloop")
   .settings(
     scriptedBufferLog := false,
@@ -347,7 +348,11 @@ lazy val sbtBloop: Project = project
     sbtPlugin := true,
     sbtVersion := SbtVersion,
     target := (file("integrations") / "sbt-bloop" / "target" / SbtVersion).getAbsoluteFile,
-    libraryDependencies += Dependencies.bloopConfig
+    libraryDependencies += Dependencies.bloopConfig,
+    buildInfoPackage := "bloop.integrations.sbt",
+    buildInfoKeys := List[BuildInfoKey](
+      "latestScalaJsVersion" -> Dependencies.scalaJs1Version
+    )
   )
 
 lazy val buildpressConfig = (project in file("buildpress-config"))

integrations/sbt-bloop/src/main/scala/bloop/integrations/sbt/SbtBloop.scala

@@ -777,8 +777,12 @@ object BloopDefaults {
       }
     } else if (pluginLabels.contains(ScalaJsPluginLabel)) {
       Def.task {
-        val emptyScalaJs = Config.JsConfig.empty
-        val scalaJsVersion = findVersion(libraryDeps, "org.scala-js").getOrElse(emptyScalaJs.version)
+        val emptyScalaJs = Config.JsConfig.empty        
+        val scalaJsVersion = libraryDeps
+          .find(module => module.organization == "org.scala-js" && module.name.startsWith("scalajs-library_"))
+          .map(_.revision)
+          .getOrElse(BuildInfo.latestScalaJsVersion)
+
         val scalaJsStage = BloopKeys.bloopScalaJSStage.value match {
           case Some(ScalaJsFastOpt) => Config.LinkerMode.Debug
           case Some(ScalaJsFullOpt) => Config.LinkerMode.Release