Make WorkspaceList.Lease implement AutoCloseable for Java 7 callers, to make...

Make WorkspaceList.Lease implement AutoCloseable for Java 7 callers, to make releasing the lease more convenient.

core/src/main/java/hudson/slaves/WorkspaceList.java

@@ -26,10 +26,12 @@ package hudson.slaves;
 import hudson.FilePath;
 import hudson.Functions;
 import hudson.model.Computer;
+import java.io.Closeable;
 
 import java.util.Date;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import javax.annotation.Nonnull;
@@ -104,7 +106,7 @@ public final class WorkspaceList {
     /**
      * Represents a leased workspace that needs to be returned later.
      */
-    public static abstract class Lease {
+    public static abstract class Lease implements /*Auto*/Closeable {
         public final @Nonnull FilePath path;
 
         protected Lease(@Nonnull FilePath path) {
@@ -117,6 +119,14 @@ public final class WorkspaceList {
          */
         public abstract void release();
 
+        /**
+         * By default, calls {@link #release}, but should be idempotent.
+         * @since TODO
+         */
+        @Override public void close() {
+            release();
+        }
+
         /**
          * Creates a dummy {@link Lease} object that does no-op in the release.
          */
@@ -261,9 +271,15 @@ public final class WorkspaceList {
      */
     private Lease lease(@Nonnull FilePath p) {
         return new Lease(p) {
+            final AtomicBoolean released = new AtomicBoolean();
             public void release() {
                 _release(path);
             }
+            @Override public void close() {
+                if (released.compareAndSet(false, true)) {
+                    release();
+                }
+            }
         };
     }
 

test/src/test/java/hudson/model/BuildExecutionTest.java

@@ -51,7 +51,7 @@ public class BuildExecutionTest {
         try {
             assertEquals(ws, lease.path);
         } finally {
-            lease.release();
+            lease.close();
         }
     }