Fix YogaLogger leakage when removing it from YogaConfig

Summary: -

Reviewed By: emilsjolander

Differential Revision: D5802035

fbshipit-source-id: 79c1f8c3cc5ddf3abd51206f23e076f2410cfc0c

java/jni/YGJNI.cpp

@@ -422,9 +422,7 @@ void jni_YGConfigSetLogger(alias_ref<jobject>, jlong nativePointer, alias_ref<jo
 
   auto context = YGConfigGetContext(config);
   if (context) {
-    auto jlogger = reinterpret_cast<global_ref<jobject> *>(context);
+    delete reinterpret_cast<global_ref<jobject> *>(context);
-    jlogger->releaseAlias();
-    delete jlogger;
   }
 
   if (logger) {

java/tests/com/facebook/yoga/YogaLoggerTest.java

@@ -0,0 +1,43 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+package com.facebook.yoga;
+
+import org.junit.Test;
+import java.lang.ref.WeakReference;
+
+import static org.junit.Assert.fail;
+
+public class YogaLoggerTest {
+  @Test
+  public void testLoggerLeak() throws Exception {
+    final YogaConfig config = new YogaConfig();
+    YogaLogger logger = new YogaLogger() {
+      @Override
+      public void log(YogaNode yogaNode, YogaLogLevel level, String message) {
+      }
+    };
+    config.setLogger(logger);
+    config.setLogger(null);
+    WeakReference<Object> ref = new WeakReference<Object>(logger);
+    // noinspection UnusedAssignment
+    logger = null;
+    // try and free for the next 5 seconds, usually it works after the
+    // first GC attempt.
+    for (int i=0; i < 50; i++) {
+      System.gc();
+      if (ref.get() == null) {
+        // free successfully
+        return;
+      }
+      Thread.sleep(100);
+    }
+    fail("YogaLogger leaked");
+  }
+}