From b8c1799d4183cf4b0ef50c21140b2acd2f6d2cfa Mon Sep 17 00:00:00 2001
From: Guillaume Martres <smarter@ubuntu.com>
Date: Fri, 24 Jul 2020 18:57:38 +0200
Subject: [PATCH] Better handling of ctrl-c while the compiler is running

Previously, the compiler tried its best to continue working after
ctrl-c, which usually resulted in a flood of error messages. This commit
takes inspiration from https://github.com/scala/scala/pull/6479 to
handle ClosedByInterruptException and InterruptedException gracefully
and avoid this.

Note that the Scala 2 PR goes further: it checks `Thread.interrupted()`
to set a global `cancelled` flag (Should we do the same with our
`Run#isCancelled` ?) and it also catches InterruptedException at the
top-level so that ctrl-c does not end up printing a stacktrace, but this
is beyond what I have the time to look at currently.
---
 .../src/dotty/tools/backend/jvm/BytecodeWriters.scala  |  7 +++++++
 compiler/src/dotty/tools/backend/jvm/GenBCode.scala    | 10 ++++++++++
 compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala |  5 +++++
 3 files changed, 22 insertions(+)

diff --git a/compiler/src/dotty/tools/backend/jvm/BytecodeWriters.scala b/compiler/src/dotty/tools/backend/jvm/BytecodeWriters.scala
index 77e3b6440713..4b6b1bf9c858 100644
--- a/compiler/src/dotty/tools/backend/jvm/BytecodeWriters.scala
+++ b/compiler/src/dotty/tools/backend/jvm/BytecodeWriters.scala
@@ -3,6 +3,8 @@ package backend
 package jvm
 
 import java.io.{ DataOutputStream, FileOutputStream, IOException, OutputStream, File => JFile }
+import java.nio.channels.ClosedByInterruptException
+import java.nio.file.Files
 import dotty.tools.io._
 import dotty.tools.dotc.report
 
@@ -112,6 +114,11 @@ trait BytecodeWriters {
       val outstream = new DataOutputStream(outfile.bufferedOutput)
 
       try outstream.write(jclassBytes, 0, jclassBytes.length)
+      catch case ex: ClosedByInterruptException =>
+        try
+          outfile.delete() // don't leave an empty or half-written classfile around after an interrupt
+        catch case _: Throwable =>
+        throw ex
       finally outstream.close()
       report.informProgress("wrote '" + label + "' to " + outfile)
     }
diff --git a/compiler/src/dotty/tools/backend/jvm/GenBCode.scala b/compiler/src/dotty/tools/backend/jvm/GenBCode.scala
index 8b5694ecff7a..5a845d4c39bf 100644
--- a/compiler/src/dotty/tools/backend/jvm/GenBCode.scala
+++ b/compiler/src/dotty/tools/backend/jvm/GenBCode.scala
@@ -22,6 +22,7 @@ import Symbols._
 import Decorators._
 
 import java.io.DataOutputStream
+import java.nio.channels.ClosedByInterruptException
 
 import dotty.tools.tasty.{ TastyBuffer, TastyHeaderUnpickler }
 
@@ -190,6 +191,8 @@ class GenBCodePipeline(val int: DottyBackendInterface)(using Context) extends BC
         else {
           try   { /*withCurrentUnit(item.cunit)*/(visit(item)) }
           catch {
+            case ex: InterruptedException =>
+              throw ex
             case ex: Throwable =>
               println(s"Error while emitting ${item.cunit.source.file.name}")
               throw ex
@@ -233,6 +236,11 @@ class GenBCodePipeline(val int: DottyBackendInterface)(using Context) extends BC
               val outTastyFile = getFileForClassfile(outF, store.name, ".tasty")
               val outstream = new DataOutputStream(outTastyFile.bufferedOutput)
               try outstream.write(binary)
+              catch case ex: ClosedByInterruptException =>
+                try
+                  outTastyFile.delete() // don't leave an empty or half-written tastyfile around after an interrupt
+                catch case _: Throwable =>
+                throw ex
               finally outstream.close()
 
               val uuid = new TastyHeaderUnpickler(binary).readHeader()
@@ -424,6 +432,8 @@ class GenBCodePipeline(val int: DottyBackendInterface)(using Context) extends BC
               addLambdaDeserialize(plainNode, serializableLambdas)
             addToQ3(item)
           } catch {
+            case ex: InterruptedException =>
+              throw ex
             case ex: Throwable =>
               println(s"Error while emitting ${item.plain.classNode.name}")
               throw ex
diff --git a/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala b/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala
index 0755b3ae5fc0..4f6785fcfa9e 100644
--- a/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala
+++ b/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala
@@ -3,6 +3,7 @@ package dotc
 package core
 
 import java.io.{IOException, File}
+import java.nio.channels.ClosedByInterruptException
 import scala.compat.Platform.currentTime
 import dotty.tools.io.{ ClassPath, ClassRepresentation, AbstractFile }
 import config.Config
@@ -343,6 +344,10 @@ abstract class SymbolLoader extends LazyType { self =>
       report.informTime("loaded " + description, start)
     }
     catch {
+      case ex: InterruptedException =>
+        throw ex
+      case ex: ClosedByInterruptException =>
+        throw new InterruptedException
       case ex: IOException =>
         signalError(ex)
       case NonFatal(ex: TypeError) =>