Retry waiting for javac

If running a single test, the pool shutdown
is likely to subvert `waitFor` the javac process.
Catch the `InterruptedException` and try again
with a timed wait of generous but finite duration,
to accommodate testing by developers. This quick
fix does not correct the race, which presumably
does not matter because of the order in which tests
are ordinarily submitted.

Author: som-snytt

compiler/test/dotty/tools/vulpix/ParallelTesting.scala

@@ -12,7 +12,7 @@ import java.nio.file.{Files, NoSuchFileException, Path, Paths}
 import java.nio.charset.{Charset, StandardCharsets}
 import java.text.SimpleDateFormat
 import java.util.{HashMap, Timer, TimerTask}
-import java.util.concurrent.{TimeUnit, TimeoutException, Executors => JExecutors}
+import java.util.concurrent.{ExecutionException, TimeUnit, TimeoutException, Executors => JExecutors}
 
 import scala.collection.mutable
 import scala.io.{Codec, Source}
@@ -494,6 +494,12 @@ trait ParallelTesting extends RunnerOrchestration { self =>
         .and("-d", targetDir.getPath)
         .withClasspath(targetDir.getPath)
 
+      def waitForJudiciously(process: Process): Int =
+        try process.waitFor()
+        catch case _: InterruptedException =>
+          try if process.waitFor(5L, TimeUnit.MINUTES) then process.exitValue() else -2
+          finally Thread.currentThread.interrupt()
+
       def compileWithJavac(fs: Array[String]) = if (fs.nonEmpty) {
         val fullArgs = Array(
           "javac",
@@ -503,7 +509,7 @@ trait ParallelTesting extends RunnerOrchestration { self =>
         val process = Runtime.getRuntime.exec(fullArgs)
         val output = Source.fromInputStream(process.getErrorStream).mkString
 
-        if (process.waitFor() != 0) Some(output)
+        if waitForJudiciously(process) != 0 then Some(output)
         else None
       } else None
 
@@ -676,7 +682,11 @@ trait ParallelTesting extends RunnerOrchestration { self =>
 
         for fut <- eventualResults do
           try fut.get()
-          catch case ex: Exception =>
+          catch
+          case ee: ExecutionException if ee.getCause.isInstanceOf[InterruptedException] =>
+            System.err.println("Interrupted (probably running after shutdown)")
+            ee.printStackTrace()
+          case ex: Exception =>
             System.err.println(ex.getMessage)
             ex.printStackTrace()