From 6f7e34fbb805664efb3d4efad9e3d9ef0c8edfc6 Mon Sep 17 00:00:00 2001
From: adazh <46544665+adazh@users.noreply.github.com>
Date: Tue, 23 Jul 2019 13:11:03 -0700
Subject: [PATCH] Added a DartExecutor API for querying # of pending channel
 callbacks (flutter/engine#10021)

---
 .../embedding/engine/dart/DartExecutor.java   | 20 +++++++++++++++++++
 .../embedding/engine/dart/DartMessenger.java  | 18 ++++++++++++++++-
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/engine/src/flutter/shell/platform/android/io/flutter/embedding/engine/dart/DartExecutor.java b/engine/src/flutter/shell/platform/android/io/flutter/embedding/engine/dart/DartExecutor.java
index 7e74f4de1a..2b8653c49d 100644
--- a/engine/src/flutter/shell/platform/android/io/flutter/embedding/engine/dart/DartExecutor.java
+++ b/engine/src/flutter/shell/platform/android/io/flutter/embedding/engine/dart/DartExecutor.java
@@ -196,6 +196,26 @@ public class DartExecutor implements BinaryMessenger {
   public void setMessageHandler(@NonNull String channel, @Nullable BinaryMessenger.BinaryMessageHandler handler) {
     messenger.setMessageHandler(channel, handler);
   }
+
+  /**
+   * Returns the number of pending channel callback replies.
+   *
+   * <p>When sending messages to the Flutter application using {@link BinaryMessenger#send(String,
+   * ByteBuffer, io.flutter.plugin.common.BinaryMessenger.BinaryReply)}, developers can optionally
+   * specify a reply callback if they expect a reply from the Flutter application.
+   *
+   * <p>This method tracks all the pending callbacks that are waiting for response, and is supposed
+   * to be called from the main thread (as other methods). Calling from a different thread could
+   * possibly capture an indeterministic internal state, so don't do it.
+   *
+   * <p>Currently, it's mainly useful for a testing framework like Espresso to determine whether all
+   * the async channel callbacks are handled and the app is idle.
+   */
+  @UiThread
+  public int getPendingChannelResponseCount() {
+    return messenger.getPendingChannelResponseCount();
+  }
+
   //------ END BinaryMessenger -----
 
   /**
diff --git a/engine/src/flutter/shell/platform/android/io/flutter/embedding/engine/dart/DartMessenger.java b/engine/src/flutter/shell/platform/android/io/flutter/embedding/engine/dart/DartMessenger.java
index 3c0dac121b..3d23b4fd09 100644
--- a/engine/src/flutter/shell/platform/android/io/flutter/embedding/engine/dart/DartMessenger.java
+++ b/engine/src/flutter/shell/platform/android/io/flutter/embedding/engine/dart/DartMessenger.java
@@ -118,6 +118,22 @@ class DartMessenger implements BinaryMessenger, PlatformMessageHandler {
     }
   }
 
+  /**
+   * Returns the number of pending channel callback replies.
+   *
+   * <p>When sending messages to the Flutter application using {@link BinaryMessenger#send(String,
+   * ByteBuffer, io.flutter.plugin.common.BinaryMessenger.BinaryReply)}, developers can optionally
+   * specify a reply callback if they expect a reply from the Flutter application.
+   *
+   * <p>This method tracks all the pending callbacks that are waiting for response, and is supposed
+   * to be called from the main thread (as other methods). Calling from a different thread could
+   * possibly capture an indeterministic internal state, so don't do it.
+   */
+  @UiThread
+  public int getPendingChannelResponseCount() {
+    return pendingReplies.size();
+  }
+
   private static class Reply implements BinaryMessenger.BinaryReply {
     @NonNull
     private final FlutterJNI flutterJNI;
@@ -141,4 +157,4 @@ class DartMessenger implements BinaryMessenger, PlatformMessageHandler {
       }
     }
   }
-}
\ No newline at end of file
+}