add JavaModule#runBackground, to allow a task to kick off processes to run in the background that only die when the task is re-run

1 files changed, 40 insertions, 0 deletions

diff --git a/scalalib/backgroundwrapper/src/mill/scalalib/backgroundwrapper/BackgroundWrapper.java b/scalalib/backgroundwrapper/src/mill/scalalib/backgroundwrapper/BackgroundWrapper.java
new file mode 100644
index 00000000..64719b53
--- /dev/null
+++ b/scalalib/backgroundwrapper/src/mill/scalalib/backgroundwrapper/BackgroundWrapper.java
@@ -0,0 +1,40 @@
+package mill.scalalib.backgroundwrapper;
+
+public class BackgroundWrapper {
+    public static void main(String[] args) throws Exception{
+        String watched = args[0];
+        String tombstone = args[1];
+        String expected = args[2];
+        Thread watcher = new Thread(new Runnable() {
+            @Override
+            public void run() {
+                while (true) {
+                    try{
+                        Thread.sleep(10);
+                        String token = new String(
+                            java.nio.file.Files.readAllBytes(java.nio.file.Paths.get(watched))
+                        );
+                        if (!token.equals(expected)) {
+                            new java.io.File(tombstone).createNewFile();
+                            System.exit(0);
+                        }
+                    }catch(Exception e){
+                        try {
+                            new java.io.File(tombstone).createNewFile();
+                        }catch(Exception e2){}
+                        System.exit(0);
+                    }
+
+                }
+            }
+        });
+        watcher.setDaemon(true);
+        watcher.start();
+        String realMain = args[3];
+        String[] realArgs = new String[args.length - 4];
+        for(int i = 0; i < args.length-4; i++){
+            realArgs[i] = args[i+4];
+        }
+        Class.forName(realMain).getMethod("main", String[].class).invoke(null, (Object)realArgs);
+    }
+}