[2.x] fix: Fixes global plugin loading (#9391)

**Problem**
Global plugin loading doesn't work.

**Solution**
1. Use ModuleID from to supply the location of global-plugin module.
2. Update pluginData with the global plugin classpath.

main/src/main/scala/sbt/internal/GlobalPlugin.scala

@@ -9,6 +9,8 @@
 package sbt
 package internal
 
+import java.io.File
+import java.net.URI
 import sbt.librarymanagement.{
   Configuration,
   Configurations,
@@ -23,21 +25,21 @@ import Configurations.{ Compile, Runtime }
 import sbt.ProjectExtra.{ extract, runUnloadHooks, setProject }
 import sbt.SlashSyntax0.*
 import sbt.librarymanagement.LibraryManagementCodec.given
-import java.io.File
 
 object GlobalPlugin {
   // constructs a sequence of settings that may be appended to a project's settings to
   //  statically add the global plugin as a classpath dependency.
   //  static here meaning that the relevant tasks for the global plugin have already been evaluated
   def inject(gp: GlobalPluginData): Seq[Setting[?]] =
+    val gpWithJar = gp.exportedJarUris.headOption
+      .fold(gp.projectID)(uri => gp.projectID.from(uri.toString))
     Seq[Setting[?]](
-      projectDependencies ++= gp.projectID +: gp.dependencies,
+      projectDependencies ++= gpWithJar +: gp.dependencies,
       resolvers := {
         val rs = resolvers.value
         (rs ++ gp.resolvers).distinct
       },
       globalPluginUpdate := gp.updateReport,
-      // TODO: these shouldn't be required (but are): the project* settings above should take care of this
       injectInternalClasspath(Runtime, gp.internalClasspath),
       injectInternalClasspath(Compile, gp.internalClasspath)
     )
@@ -76,13 +78,16 @@ object GlobalPlugin {
     val taskInit = Def.task {
       val intcp = (Runtime / internalDependencyClasspath).value
       val prods = (Runtime / exportedProducts).value
+      val converter = fileConverter.value
+      val exportedJarUris = prods.map(a => converter.toPath(a.data).toUri).toVector
 
       GlobalPluginData(
         projectID.value,
         projectDependencies.value,
         resolvers.value.toVector,
         (Runtime / fullClasspath).value,
-        (prods ++ intcp).distinct
+        (prods ++ intcp).distinct,
+        exportedJarUris
       )(updateReport.value)
     }
     val resolvedTaskInit = taskInit.mapReferenced(Project.replaceThis(p))
@@ -120,7 +125,8 @@ final case class GlobalPluginData(
     dependencies: Seq[ModuleID],
     resolvers: Vector[Resolver],
     fullClasspath: Classpath,
-    internalClasspath: Classpath
+    internalClasspath: Classpath,
+    exportedJarUris: Vector[URI],
 )(val updateReport: UpdateReport)
 final case class GlobalPlugin(
     data: GlobalPluginData,

main/src/main/scala/sbt/internal/Load.scala

@@ -1411,41 +1411,43 @@ private[sbt] object Load {
       case None     => Nil
 
   /** These are the settings defined when loading a project "meta" build. */
-  val autoPluginSettings: Seq[Setting[?]] = inScope(GlobalScope.rescope(LocalRootProject))(
-    Seq(
-      sbtPlugin :== true,
-      isMetaBuild :== true,
-      pluginData := Def.uncached {
-        val prod = (Configurations.Runtime / exportedProducts).value
-        val internalCp = (Configurations.Runtime / internalDependencyClasspath).value
-        val cp = (Configurations.Runtime / fullClasspath).value
-        val opts = (Configurations.Compile / scalacOptions).value
-        val javaOpts = (Configurations.Compile / javacOptions).value
-        val unmanagedSrcDirs = (Configurations.Compile / unmanagedSourceDirectories).value
-        val unmanagedSrcs = (Configurations.Compile / unmanagedSources).value
-        val managedSrcDirs = (Configurations.Compile / managedSourceDirectories).value
-        val managedSrcs = (Configurations.Compile / managedSources).value
-        val buildTarget = (Configurations.Compile / bspTargetIdentifier).value
-        val converter = fileConverter.value
-        PluginData(
-          removeEntries(cp, prod),
-          prod,
-          Some(fullResolvers.value.toVector),
-          Some(update.value),
-          opts,
-          javaOpts,
-          unmanagedSrcDirs,
-          unmanagedSrcs,
-          managedSrcDirs,
-          managedSrcs,
-          Some(buildTarget),
-          converter,
-          internalCp,
-        )
-      },
-      onLoadMessage := ("loading project definition from " + baseDirectory.value)
+  def autoPluginSettings(config: LoadBuildConfiguration): Seq[Setting[?]] =
+    inScope(GlobalScope.rescope(LocalRootProject))(
+      Seq(
+        sbtPlugin :== true,
+        isMetaBuild :== true,
+        pluginData := Def.uncached {
+          val gpClasspath = globalPluginClasspath(config.globalPlugin)
+          val prod = (Configurations.Runtime / exportedProducts).value
+          val internalCp = (Configurations.Runtime / internalDependencyClasspath).value
+          val cp = (Configurations.Runtime / fullClasspath).value
+          val opts = (Configurations.Compile / scalacOptions).value
+          val javaOpts = (Configurations.Compile / javacOptions).value
+          val unmanagedSrcDirs = (Configurations.Compile / unmanagedSourceDirectories).value
+          val unmanagedSrcs = (Configurations.Compile / unmanagedSources).value
+          val managedSrcDirs = (Configurations.Compile / managedSourceDirectories).value
+          val managedSrcs = (Configurations.Compile / managedSources).value
+          val buildTarget = (Configurations.Compile / bspTargetIdentifier).value
+          val converter = fileConverter.value
+          PluginData(
+            (removeEntries(cp, prod) ++ gpClasspath).distinct,
+            prod,
+            Some(fullResolvers.value.toVector),
+            Some(update.value),
+            opts,
+            javaOpts,
+            unmanagedSrcDirs,
+            unmanagedSrcs,
+            managedSrcDirs,
+            managedSrcs,
+            Some(buildTarget),
+            converter,
+            internalCp,
+          )
+        },
+        onLoadMessage := ("loading project definition from " + baseDirectory.value)
+      )
     )
-  )
 
   private def removeEntries(
       cp: Def.Classpath,
@@ -1459,7 +1461,7 @@ private[sbt] object Load {
   def enableSbtPlugin(config: LoadBuildConfiguration): LoadBuildConfiguration =
     config.copy(
       injectSettings = config.injectSettings.copy(
-        global = autoPluginSettings ++ config.injectSettings.global,
+        global = autoPluginSettings(config) ++ config.injectSettings.global,
         project = config.pluginManagement.inject ++ config.injectSettings.project
       )
     )