[2.x] fix: clear compiler bridge zinc cache on reboot dev (#9057)

Reboot dev now removes zinc/org.scala-sbt under the resolved global zinc
directory (same layout as ZincComponentManager secondary cache).

Closes #5735

main-command/src/main/scala/sbt/BasicCommandStrings.scala

@@ -149,7 +149,9 @@ $HelpCommand <regular expression>
     remaining commands with the exception that the JVM is not shut down.
 
   If 'dev' is specified, the current sbt artifacts from the boot directory
-    (`~/.sbt/boot` by default) are deleted before restarting.
+    (under the default global base; `sbt.global.base` selects that location) are deleted
+    before restarting, and the compiler bridge secondary cache at `zinc/org.scala-sbt`
+    (honoring `sbt.global.base` and `sbt.global.zinc`) is removed.
   This forces an update of sbt and Scala, which is useful when working with development
     versions of sbt.
   If 'full' is specified, the boot directory is wiped out before restarting.

main/src/main/scala/sbt/MainLoop.scala

@@ -22,6 +22,8 @@ import sbt.internal.util.{
   Terminal as ITerminal
 }
 import sbt.io.{ IO, Using }
+import sbt.io.syntax.*
+import sbt.librarymanagement.SbtArtifacts
 import sbt.protocol.*
 import sbt.util.{ Logger, LoggerContext }
 
@@ -75,6 +77,10 @@ private[sbt] object MainLoop:
       case e: RebootCurrent =>
         deleteLastLog(logBacking)
         deleteCurrentArtifacts(state)
+        deleteZincBridgeSecondaryCache(
+          state.log,
+          BuildPaths.getZincDirectory(state, BuildPaths.getGlobalBase(state)),
+        )
         throw new xsbti.FullReload(e.arguments.toArray, false)
       case NonFatal(e) =>
         System.err.println(
@@ -89,7 +95,6 @@ private[sbt] object MainLoop:
 
   /** Deletes the current sbt artifacts from boot. */
   private[sbt] def deleteCurrentArtifacts(state: State): Unit = {
-    import sbt.io.syntax.*
     val provider = state.configuration.provider
     val appId = provider.id
     // If we can obtain boot directory more accurately it'd be better.
@@ -109,6 +114,13 @@ private[sbt] object MainLoop:
     }
   }
 
+  /** Removes the Zinc compiler bridge secondary cache (`zincDir/org.scala-sbt`). */
+  private[sbt] def deleteZincBridgeSecondaryCache(log: Logger, zincDir: File): Unit =
+    val bridgeCache = zincDir / SbtArtifacts.Organization
+    if bridgeCache.exists() then
+      log.info(s"deleting $bridgeCache")
+      IO.delete(bridgeCache)
+
   /** Runs the next sequence of commands with global logging in place. */
   def runWithNewLog(state: State, logBacking: GlobalLogBacking): RunNext =
     Using.fileWriter(append = true)(logBacking.file) { writer =>

main/src/test/scala/sbt/MainLoopZincCacheTest.scala

@@ -0,0 +1,49 @@
+/*
+ * sbt
+ * Copyright 2023, Scala center
+ * Copyright 2011 - 2022, Lightbend, Inc.
+ * Copyright 2008 - 2010, Mark Harrah
+ * Licensed under Apache License 2.0 (see LICENSE)
+ */
+
+package sbt
+
+import java.io.File
+
+import sbt.internal.util.{ ConsoleOut, GlobalLogging, MainAppender }
+import sbt.io.IO
+import sbt.io.syntax.*
+import sbt.librarymanagement.SbtArtifacts
+import sbt.util.Logger
+
+object MainLoopZincCacheTest extends verify.BasicTestSuite:
+
+  private def withTestLog[A](f: Logger => A): A =
+    val logFile = File.createTempFile("sbt-mlz", ".log")
+    try
+      val gl = GlobalLogging.initial(
+        MainAppender.globalDefault(ConsoleOut.globalProxy),
+        logFile,
+        ConsoleOut.globalProxy
+      )
+      f(gl.full)
+    finally IO.delete(logFile)
+
+  test("deleteZincBridgeSecondaryCache removes org.scala-sbt under zincDir"):
+    IO.withTemporaryDirectory: tmp =>
+      val zincRoot = tmp / "zinc"
+      val bridge = zincRoot / SbtArtifacts.Organization
+      IO.write(bridge / "marker.txt", "cached")
+      withTestLog: log =>
+        MainLoop.deleteZincBridgeSecondaryCache(log, zincRoot)
+      assert(!bridge.exists(), s"expected $bridge deleted")
+
+  test("deleteZincBridgeSecondaryCache is a no-op when org.scala-sbt is absent"):
+    IO.withTemporaryDirectory: tmp =>
+      val zincRoot = tmp / "zinc"
+      IO.createDirectory(zincRoot)
+      withTestLog: log =>
+        MainLoop.deleteZincBridgeSecondaryCache(log, zincRoot)
+      assert(zincRoot.exists())
+
+end MainLoopZincCacheTest