Use ProcessHandle instead of shell script to check for parent process

See #1025

Signed-off-by: David Thompson <davthomp@redhat.com>

Author: datho7561

org.eclipse.lemminx/src/main/java/org/eclipse/lemminx/commons/ParentProcessWatcher.java

@@ -12,19 +12,14 @@
  *******************************************************************************/
 package org.eclipse.lemminx.commons;
 
-import static org.eclipse.lemminx.utils.platform.Platform.isWindows;
-
-import java.io.IOException;
+import java.util.Optional;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.TimeUnit;
 import java.util.function.Function;
-import java.util.logging.Level;
 import java.util.logging.Logger;
 
-import com.google.common.io.Closeables;
-
 import org.eclipse.lsp4j.jsonrpc.MessageConsumer;
 import org.eclipse.lsp4j.services.LanguageServer;
 
@@ -36,7 +31,6 @@
 public final class ParentProcessWatcher implements Runnable, Function<MessageConsumer, MessageConsumer> {
 
 	private static final Logger LOGGER = Logger.getLogger(ParentProcessWatcher.class.getName());
-	private static final boolean isJava1x = System.getProperty("java.version").startsWith("1.");
 
 	/**
 	 * Exit code returned when XML Language Server is forced to exit.
@@ -46,9 +40,9 @@ public final class ParentProcessWatcher implements Runnable, Function<MessageCon
 	private static final long INACTIVITY_DELAY_SECS = 30 * 1000;
 	private static final int POLL_DELAY_SECS = 10;
 	private volatile long lastActivityTime;
-	private final ProcessLanguageServer server;
 	private ScheduledFuture<?> task;
 	private ScheduledExecutorService service;
+	private ProcessLanguageServer server;
 
 	public interface ProcessLanguageServer extends LanguageServer {
 
@@ -84,55 +78,8 @@ private boolean parentProcessStillRunning() {
 		if (pid == 0 || lastActivityTime > (System.currentTimeMillis() - INACTIVITY_DELAY_SECS)) {
 			return true;
 		}
-		String command;
-		if (isWindows) {
-			command = "cmd /c \"tasklist /FI \"PID eq " + pid + "\" | findstr " + pid + "\"";
-		} else {
-			command = "kill -0 " + pid;
-		}
-		Process process = null;
-		boolean finished = false;
-		try {
-			process = Runtime.getRuntime().exec(command);
-			finished = process.waitFor(POLL_DELAY_SECS, TimeUnit.SECONDS);
-			if (!finished) {
-				process.destroy();
-				finished = process.waitFor(POLL_DELAY_SECS, TimeUnit.SECONDS); // wait for the process to stop
-			}
-			if (isWindows && finished && process.exitValue() > 1) {
-				// the tasklist command should return 0 (parent process exists) or 1 (parent process doesn't exist)
-				LOGGER.warning("The tasklist command: '" + command + "' returns " + process.exitValue());
-				return true;
-			}
-			return !finished || process.exitValue() == 0;
-		} catch (IOException | InterruptedException e) {
-			LOGGER.log(Level.WARNING, e.getMessage(), e);
-			return true;
-		} finally {
-			if (process != null) {
-				if (!finished) {
-					process.destroyForcibly();
-				}
-				// Terminating or destroying the Process doesn't close the process handle on Windows.
-				// It is only closed when the Process object is garbage collected (in its finalize() method).
-				// On Windows, when the Java LS is idle, we need to explicitly request a GC,
-				// to prevent an accumulation of zombie processes, as finalize() will be called.
-				if (isWindows) {
-					// Java >= 9 doesn't close the handle when the process is garbage collected
-					// We need to close the opened streams
-					if (!isJava1x) {
-						Closeables.closeQuietly(process.getInputStream());
-						Closeables.closeQuietly(process.getErrorStream());
-						try {
-							Closeables.close(process.getOutputStream(), false);
-						} catch (IOException e) {
-						}
-					}
-					System.gc();
-				}
-			}
-		}
-
+		Optional<ProcessHandle> optionalHandle = ProcessHandle.of(pid);
+		return !optionalHandle.isEmpty() && optionalHandle.get().isAlive();
 	}
 
 	@Override