Reviewed exitCode handling

Propagate server stop because of version change as exit code.

2 files changed, 19 insertions, 8 deletions

diff --git a/main/client/src/MillClientMain.java b/main/client/src/MillClientMain.java
index 3857caff..dc144f99 100644
--- a/main/client/src/MillClientMain.java
+++ b/main/client/src/MillClientMain.java
@@ -10,6 +10,12 @@ import java.nio.channels.FileChannel;
 import java.util.*;
 
 public class MillClientMain {
+
+    // use methods instead of constants to avoid inlining by compiler
+    public static final int ExitClientCodeCannotReadFromExitCodeFile() { return 1; }
+	public static final int ExitServerCodeWhenIdle() { return 0; }
+	public static final int ExitServerCodeWhenVersionMismatch() { return 101; }
+
     static void initServer(String lockBase, boolean setJnaNoSys) throws IOException,URISyntaxException{
         String[] selfJars = System.getProperty("MILL_CLASSPATH").split(",");
 
@@ -56,7 +62,8 @@ public class MillClientMain {
             System.setProperty("jna.nosys", "true");
         }
         int index = 0;
-        while (index < 5) {
+        final int processLimit = 5;
+        while (index < processLimit) {
             index += 1;
             String lockBase = "out/mill-worker-" + index;
             new java.io.File(lockBase).mkdirs();
@@ -91,7 +98,7 @@ public class MillClientMain {
 
             }
         }
-        throw new Exception("Reached max process limit: " + 5);
+        throw new Exception("Reached max process limit: " + processLimit);
     }
 
     public static int run(String lockBase,
@@ -151,10 +158,10 @@ public class MillClientMain {
 
         locks.serverLock.await();
 
-        try(FileInputStream fos = new FileInputStream(lockBase + "/exitCode")){
-            return Integer.parseInt(new BufferedReader(new InputStreamReader(fos)).readLine());
+        try(FileInputStream fis = new FileInputStream(lockBase + "/exitCode")){
+            return Integer.parseInt(new BufferedReader(new InputStreamReader(fis)).readLine());
         } catch(Throwable e){
-            return 1;
+            return ExitClientCodeCannotReadFromExitCodeFile();
         } finally{
             ioSocket.close();
         }
diff --git a/main/src/main/MillServerMain.scala b/main/src/main/MillServerMain.scala
index 55cef632..862daaf7 100644
--- a/main/src/main/MillServerMain.scala
+++ b/main/src/main/MillServerMain.scala
@@ -37,9 +37,9 @@ object MillServerMain extends mill.main.MillServerMain[Evaluator.State]{
       def handle(sig: Signal) = {} // do nothing
     })
     new Server(
-      args0(0),
+      lockBase = args0(0),
       this,
-      () => System.exit(0),
+      () => System.exit(MillClientMain.ExitServerCodeWhenIdle()),
       300000,
       mill.main.client.Locks.files(args0(0))
     ).run()
@@ -124,7 +124,11 @@ class Server[T](lockBase: String,
     if (clientMillVersion != serverMillVersion) {
       // FIXME: exiting with 0 isn't correct, see https://github.com/lihaoyi/mill/issues/557
       stdout.println(s"Mill version changed ($serverMillVersion -> $clientMillVersion), re-starting server")
-      System.exit(0)
+      java.nio.file.Files.write(
+        java.nio.file.Paths.get(lockBase + "/exitCode"),
+        s"${MillClientMain.ExitServerCodeWhenVersionMismatch()}".getBytes()
+      )
+      System.exit(MillClientMain.ExitServerCodeWhenVersionMismatch())
     }
     val args = Util.parseArgs(argStream)
     val env = Util.parseMap(argStream)