From 3c9826f4f4f9a55983b61dc31b23bf9e45d81d64 Mon Sep 17 00:00:00 2001
From: Amina Adewusi <amina.adewusi@guardian.co.uk>
Date: Fri, 20 Aug 2021 17:45:14 +0100
Subject: [PATCH] Fixes shutdown hook error in timing report

This fixes the closed channel exception generated when running
sbt -timings help. This bug was introduced in sbt 1.4 where a wrapper
was created (Terminal.scala) around the terminal. This meant that the
shutdown hook which had been used previously was no longer working.

This has been fixed by avoiding the use of the JVM shutdown hook and
instead manually running the thunk at a place in the code where
the programme is still able to respond.
---
 main/src/main/scala/sbt/EvaluateTask.scala    | 24 +++++++++++++++++++
 .../scala/sbt/internal/CommandExchange.scala  |  1 +
 .../main/scala/sbt/internal/TaskTimings.scala |  3 ++-
 3 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/main/src/main/scala/sbt/EvaluateTask.scala b/main/src/main/scala/sbt/EvaluateTask.scala
index 55da21c94..8d45104cb 100644
--- a/main/src/main/scala/sbt/EvaluateTask.scala
+++ b/main/src/main/scala/sbt/EvaluateTask.scala
@@ -9,6 +9,7 @@ package sbt
 
 import java.io.File
 import java.util.concurrent.atomic.AtomicReference
+
 import sbt.Def.{ ScopedKey, Setting, dummyState }
 import sbt.Keys.{ TaskProgress => _, name => _, _ }
 import sbt.Project.richInitializeTask
@@ -28,6 +29,7 @@ import sbt.internal.bsp.BuildTargetIdentifier
 import scala.annotation.nowarn
 import scala.Console.RED
 import scala.concurrent.duration.Duration
+import scala.util.control.NonFatal
 
 /**
  * An API that allows you to cancel executing tasks upon some signal.
@@ -169,6 +171,28 @@ object EvaluateTask {
     if (SysProp.taskTimingsOnShutdown) Some(sharedProgress)
     else None
 
+  private val capturedThunk = new AtomicReference[() => Unit]()
+  def onShutdown(): Unit = {
+    val thunk = capturedThunk.getAndSet(null)
+    if (thunk != null) thunk()
+  }
+  // our own implementation of shutdown hook, because the "sbt -timings help" command was not working with the JVM shutdown hook,
+  // which is a little hard to control.
+  def addShutdownHandler[A](thunk: () => A): Unit = {
+    capturedThunk
+      .set(
+        () =>
+          try {
+            thunk()
+            ()
+          } catch {
+            case NonFatal(e) =>
+              System.err.println(s"Caught exception running shutdown hook: $e")
+              e.printStackTrace(System.err)
+          }
+      )
+  }
+
   lazy private val sharedTraceEvent = new TaskTraceEvent()
   def taskTraceEvent: Option[ExecuteProgress[Task]] =
     if (SysProp.traces) {
diff --git a/main/src/main/scala/sbt/internal/CommandExchange.scala b/main/src/main/scala/sbt/internal/CommandExchange.scala
index 36059cdc3..992fb8548 100644
--- a/main/src/main/scala/sbt/internal/CommandExchange.scala
+++ b/main/src/main/scala/sbt/internal/CommandExchange.scala
@@ -290,6 +290,7 @@ private[sbt] final class CommandExchange {
     // interrupt and kill the thread
     server.foreach(_.shutdown())
     server = None
+    EvaluateTask.onShutdown
   }
 
   // This is an interface to directly respond events.
diff --git a/main/src/main/scala/sbt/internal/TaskTimings.scala b/main/src/main/scala/sbt/internal/TaskTimings.scala
index 6f421e829..fe814ccd5 100644
--- a/main/src/main/scala/sbt/internal/TaskTimings.scala
+++ b/main/src/main/scala/sbt/internal/TaskTimings.scala
@@ -8,6 +8,7 @@
 package sbt
 package internal
 
+import sbt.EvaluateTask.addShutdownHandler
 import sbt.internal.util.{ ConsoleOut, RMap }
 import sbt.util.{ Level, Logger }
 
@@ -38,7 +39,7 @@ private[sbt] final class TaskTimings(reportOnShutdown: Boolean, logger: Logger)
 
   if (reportOnShutdown) {
     start = System.nanoTime
-    ShutdownHooks.add(() => report())
+    addShutdownHandler(() => report())
   }
 
   override def initial(): Unit = {