SI-10007 sys.process thread sync

A previous change to replace `SyncVar.set` with `SyncVar.put`
breaks things.

This commit tweaks the thread synchronizing in `sys.process`
to actually use `SyncVar` to sync and pass a var.

Joining the thread about to exit is superfluous.

A result is put exactly once, and consumers use
non-destructive `get`.

Note that as usual, avoid kicking off threads in a static
context, since class loading cycles are somewhat dicier
with 2.12 lambdas. In particular, REPL is a static context
by default.

SI-10007 Clarify deprecation message

The message on `set` was self-fulfilling, as it didn't
hint that `put` has different semantics.

So explain why `put` helps avoid errors instead of
creating them.

SI-10007 Always set exit value

Always put a value to exit code, defaulting to None.

Also clean up around tuple change to unfortunately
named Future.apply. Very hard to follow those types.

Date command pollutes output, so tweak test.

2 files changed, 26 insertions, 0 deletions

diff --git a/test/junit/scala/sys/process/t7350.scala b/test/junit/scala/sys/process/PipedProcessTest.scala
index 9fdcac8ccc..53f053e9aa 100644
--- a/test/junit/scala/sys/process/t7350.scala
+++ b/test/junit/scala/sys/process/PipedProcessTest.scala
@@ -12,6 +12,7 @@ import scala.concurrent.ExecutionContext.Implicits.global
 import scala.util.control.Exception.ignoring
 
 // Each test normally ends in a moment, but for failure cases, waits until one second.
+// SI-7350, SI-8768
 
 @RunWith(classOf[JUnit4])
 class PipedProcessTest {
diff --git a/test/junit/scala/sys/process/ProcessTest.scala b/test/junit/scala/sys/process/ProcessTest.scala
new file mode 100644
index 0000000000..f6d779c2c8
--- /dev/null
+++ b/test/junit/scala/sys/process/ProcessTest.scala
@@ -0,0 +1,25 @@
+package scala.sys.process
+
+import java.io.ByteArrayInputStream
+// should test from outside the package to ensure implicits work
+//import scala.sys.process._
+import scala.util.Properties._
+
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+import org.junit.Test
+import org.junit.Assert.assertEquals
+
+@RunWith(classOf[JUnit4])
+class ProcessTest {
+  private def testily(body: => Unit) = if (!isWin) body
+  @Test def t10007(): Unit = testily {
+    val res = ("cat" #< new ByteArrayInputStream("lol".getBytes)).!!
+    assertEquals("lol\n", res)
+  }
+  // test non-hanging
+  @Test def t10055(): Unit = testily {
+    val res = ("cat" #< ( () => -1 ) ).!
+    assertEquals(0, res)
+  }
+}