Fix flaky EspressoIdleTest#onIdle_backgroundLooper_with_TestLooperManager.

Previously the TestLooperManager could be released while interrogation was occurring.

With this change, LooperIdlingResourceInterrogationHandler will release the TestLooperManager on
the Looper thread instead of immediately.

PiperOrigin-RevId: 750706298

Author: brettchabot

espresso/core/java/androidx/test/espresso/base/LooperIdlingResourceInterrogationHandler.java

@@ -70,6 +70,7 @@ public boolean barrierUp() {
   private volatile boolean started = false;
   private volatile Looper looper = null;
   private volatile boolean idle = true;
+  private volatile boolean releasing = false;
 
   private volatile TestLooperManagerCompat testLooperManager = null;
 
@@ -101,7 +102,11 @@ public void run() {
                 ir.looper = Looper.myLooper();
                 ir.testLooperManager = TestLooperManagerCompat.acquire(ir.looper);
                 ir.started = true;
-                new Interrogator().loopAndInterrogate(ir.testLooperManager, ir);
+                try {
+                  new Interrogator().loopAndInterrogate(ir.testLooperManager, ir);
+                } finally {
+                  ir.testLooperManager.release();
+                }
               }
             });
 
@@ -118,41 +123,37 @@ public String getMessage() {
 
   @Override
   public void quitting() {
-    if (testLooperManager != null) {
-      testLooperManager.release();
-      testLooperManager = null;
-    }
-    transitionToIdle();
+    releasing = true;
   }
 
   @Override
   public boolean queueEmpty() {
     transitionToIdle();
-    return true;
+    return !releasing;
   }
 
   @Override
   public boolean taskDueLong() {
     transitionToIdle();
-    return true;
+    return !releasing;
   }
 
   @Override
   public boolean beforeTaskDispatch() {
     idle = false;
-    return true;
+    return !releasing;
   }
 
   @Override
   public boolean taskDueSoon() {
     idle = false;
-    return true;
+    return !releasing;
   }
 
   @Override
   public boolean barrierUp() {
     idle = false;
-    return true;
+    return !releasing;
   }
 
   @Override
@@ -162,7 +163,7 @@ public Void get() {
 
   @Override
   public boolean isIdleNow() {
-    if (!started) {
+    if (!started || releasing) {
       return false;
     }
     if (idle) {
@@ -193,9 +194,8 @@ private void transitionToIdle() {
   }
 
   public void release() {
-    if (testLooperManager != null) {
-      testLooperManager.release();
-      testLooperManager = null;
-    }
+    releasing = true;
+    // post a message to looper to wake up interrogator if necessary
+    new Handler(looper).post(() -> {});
   }
 }

espresso/core/javatests/androidx/test/espresso/base/EspressoIdleTest.java

@@ -13,6 +13,7 @@
 import androidx.test.espresso.Espresso;
 import androidx.test.espresso.IdlingRegistry;
 import androidx.test.ext.junit.runners.AndroidJUnit4;
+import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.atomic.AtomicBoolean;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -92,14 +93,21 @@ public void onIdle_backgroundLooper_with_TestLooperManager() throws InterruptedE
     Looper looper = ht.getLooper();
 
     IdlingRegistry.getInstance().registerLooperAsIdlingResource(looper);
+    Espresso.onIdle();
     AtomicBoolean wasRun = new AtomicBoolean(false);
     new Handler(looper).post(() -> wasRun.set(true));
     Espresso.onIdle();
     assertThat(wasRun.get()).isTrue();
-    IdlingRegistry.getInstance().unregisterLooperAsIdlingResource(looper);
 
+    IdlingRegistry.getInstance().unregisterLooperAsIdlingResource(looper);
     Espresso.onIdle();
 
+    // The Looper IdlingResource releases its TestLooperManager asynchronously on
+    // the Looper thread. Post and wait for the Looper thread to clear
+    CountDownLatch latch = new CountDownLatch(1);
+    new Handler(looper).post(() -> latch.countDown());
+    latch.await();
+
     TestLooperManager manager = getInstrumentation().acquireLooperManager(looper);
     assertThat(manager).isNotNull();
     manager.release();