From eefd8153d93107c04aeb7a0fcd5542ebaced8b26 Mon Sep 17 00:00:00 2001
From: Brett Chabot <brettchabot@google.com>
Date: Fri, 6 Dec 2024 15:28:36 -0800
Subject: [PATCH] Only drain main looper when it is paused.

ControlledLooper.drainMainThreadUntilIdle was created
so Robolectric can manually execute tasks when main looper is paused.

Now with the introduction of INSTRUMENTATION_TEST looper mode with a
free running looper, it doesn't make sense to always idle the main looper,
and could lead to deviation of behavior between a test run with Robolectric
INSTRUMENTATION_TEST mode and real android.

This commit changes drainMainThreadUntilIdle so its a no-op if main looper
is not paused.

PiperOrigin-RevId: 703634485
---
 espresso/CHANGELOG.md                                      | 2 ++
 .../test/espresso/base/ThreadPoolExecutorExtractor.java    | 7 +++++++
 2 files changed, 9 insertions(+)

diff --git a/espresso/CHANGELOG.md b/espresso/CHANGELOG.md
index a1888dc4e..a0993d9c1 100644
--- a/espresso/CHANGELOG.md
+++ b/espresso/CHANGELOG.md
@@ -16,6 +16,8 @@ The following artifacts were released:
 
 **Bug Fixes**
 
+* Fix deadlock in espresso in Robolectric INSTRUMENTATION_TEST + paused looper.
+
 **New Features**
 
 **Breaking Changes**
diff --git a/espresso/core/java/androidx/test/espresso/base/ThreadPoolExecutorExtractor.java b/espresso/core/java/androidx/test/espresso/base/ThreadPoolExecutorExtractor.java
index 0cd67686e..b016f7d44 100644
--- a/espresso/core/java/androidx/test/espresso/base/ThreadPoolExecutorExtractor.java
+++ b/espresso/core/java/androidx/test/espresso/base/ThreadPoolExecutorExtractor.java
@@ -19,6 +19,8 @@
 import android.os.Handler;
 import android.os.Looper;
 import androidx.annotation.Nullable;
+import androidx.test.internal.platform.ServiceLoaderWrapper;
+import androidx.test.internal.platform.os.ControlledLooper;
 import java.lang.reflect.Field;
 import java.util.concurrent.Callable;
 import java.util.concurrent.CountDownLatch;
@@ -42,6 +44,10 @@ final class ThreadPoolExecutorExtractor {
   private static final String MODERN_ASYNC_TASK_FIELD_NAME = "THREAD_POOL_EXECUTOR";
   private final Handler mainHandler;
 
+  private final ControlledLooper controlledLooper =
+      ServiceLoaderWrapper.loadSingleService(
+          ControlledLooper.class, () -> ControlledLooper.NO_OP_CONTROLLED_LOOPER);
+
   @Inject
   ThreadPoolExecutorExtractor(Looper looper) {
     mainHandler = new Handler(looper);
@@ -85,6 +91,7 @@ public void run() {
             }
           });
       try {
+        controlledLooper.drainMainThreadUntilIdle();
         latch.await();
       } catch (InterruptedException ie) {
         if (!futureToRun.isDone()) {