Set deep linking flag to true by default (flutter/engine#52350)

doc: flutter.dev/go/deep-link-flag-migration

Action item: make sure customers are aware of this change before merging
this PR.

## Pre-launch Checklist

- [ ] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [ ] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [ ] I read and followed the [Flutter Style Guide] and the [C++,
Objective-C, Java style guides].
- [ ] I listed at least one issue that this PR fixes in the description
above.
- [ ] I added new tests to check the change I am making or feature I am
adding, or the PR is [test-exempt]. See [testing the engine] for
instructions on writing and running engine tests.
- [ ] I updated/added relevant documentation (doc comments with `///`).
- [ ] I signed the [CLA].
- [ ] All existing and new tests are passing.

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engine/src/flutter/shell/platform/android/io/flutter/embedding/android/FlutterActivity.java

@@ -18,9 +18,9 @@ import static io.flutter.embedding.android.FlutterActivityLaunchConfigs.EXTRA_DA
 import static io.flutter.embedding.android.FlutterActivityLaunchConfigs.EXTRA_DESTROY_ENGINE_WITH_ACTIVITY;
 import static io.flutter.embedding.android.FlutterActivityLaunchConfigs.EXTRA_ENABLE_STATE_RESTORATION;
 import static io.flutter.embedding.android.FlutterActivityLaunchConfigs.EXTRA_INITIAL_ROUTE;
-import static io.flutter.embedding.android.FlutterActivityLaunchConfigs.HANDLE_DEEPLINKING_META_DATA_KEY;
 import static io.flutter.embedding.android.FlutterActivityLaunchConfigs.INITIAL_ROUTE_META_DATA_KEY;
 import static io.flutter.embedding.android.FlutterActivityLaunchConfigs.NORMAL_THEME_META_DATA_KEY;
+import static io.flutter.embedding.android.FlutterActivityLaunchConfigs.deepLinkEnabled;
 
 import android.annotation.TargetApi;
 import android.app.Activity;
@@ -1404,9 +1404,7 @@ public class FlutterActivity extends Activity
   public boolean shouldHandleDeeplinking() {
     try {
       Bundle metaData = getMetaData();
-      boolean shouldHandleDeeplinking =
+      return deepLinkEnabled(metaData);
-          metaData != null ? metaData.getBoolean(HANDLE_DEEPLINKING_META_DATA_KEY) : false;
-      return shouldHandleDeeplinking;
     } catch (PackageManager.NameNotFoundException e) {
       return false;
     }

engine/src/flutter/shell/platform/android/io/flutter/embedding/android/FlutterActivityLaunchConfigs.java

@@ -4,6 +4,8 @@
 
 package io.flutter.embedding.android;
 
+import android.os.Bundle;
+
 /** Collection of Flutter launch configuration options. */
 // This class is public so that Flutter app developers can reference
 // BackgroundMode
@@ -41,5 +43,24 @@ public class FlutterActivityLaunchConfigs {
     transparent
   }
 
+  /**
+   * Whether to handle the deeplinking.
+   *
+   * <p>The default implementation looks {@code <meta-data>} called {@link
+   * FlutterActivityLaunchConfigs#HANDLE_DEEPLINKING_META_DATA_KEY} within the Android manifest
+   * definition for this {@code FlutterActivity}.
+   *
+   * <p>Defaults to {@code true}.
+   */
+  public static boolean deepLinkEnabled(Bundle metaData) {
+    // Check if metadata is not null and contains the HANDLE_DEEPLINKING_META_DATA_KEY.
+    if (metaData != null && metaData.containsKey(HANDLE_DEEPLINKING_META_DATA_KEY)) {
+      return metaData.getBoolean(HANDLE_DEEPLINKING_META_DATA_KEY);
+    } else {
+      // Return true if the deep linking flag is not found in metadata.
+      return true;
+    }
+  }
+
   private FlutterActivityLaunchConfigs() {}
 }

engine/src/flutter/shell/platform/android/io/flutter/embedding/android/FlutterFragmentActivity.java

@@ -16,9 +16,9 @@ import static io.flutter.embedding.android.FlutterActivityLaunchConfigs.EXTRA_DA
 import static io.flutter.embedding.android.FlutterActivityLaunchConfigs.EXTRA_DART_ENTRYPOINT_ARGS;
 import static io.flutter.embedding.android.FlutterActivityLaunchConfigs.EXTRA_DESTROY_ENGINE_WITH_ACTIVITY;
 import static io.flutter.embedding.android.FlutterActivityLaunchConfigs.EXTRA_INITIAL_ROUTE;
-import static io.flutter.embedding.android.FlutterActivityLaunchConfigs.HANDLE_DEEPLINKING_META_DATA_KEY;
 import static io.flutter.embedding.android.FlutterActivityLaunchConfigs.INITIAL_ROUTE_META_DATA_KEY;
 import static io.flutter.embedding.android.FlutterActivityLaunchConfigs.NORMAL_THEME_META_DATA_KEY;
+import static io.flutter.embedding.android.FlutterActivityLaunchConfigs.deepLinkEnabled;
 
 import android.content.Context;
 import android.content.Intent;
@@ -695,9 +695,7 @@ public class FlutterFragmentActivity extends FragmentActivity
   protected boolean shouldHandleDeeplinking() {
     try {
       Bundle metaData = getMetaData();
-      boolean shouldHandleDeeplinking =
+      return deepLinkEnabled(metaData);
-          metaData != null ? metaData.getBoolean(HANDLE_DEEPLINKING_META_DATA_KEY) : false;
-      return shouldHandleDeeplinking;
     } catch (PackageManager.NameNotFoundException e) {
       return false;
     }

engine/src/flutter/shell/platform/android/test/io/flutter/embedding/android/FlutterActivityTest.java

@@ -332,8 +332,8 @@ public class FlutterActivityTest {
     Bundle bundle = new Bundle();
     FlutterActivity spyFlutterActivity = spy(flutterActivity);
     when(spyFlutterActivity.getMetaData()).thenReturn(bundle);
-    // Empty bundle should return false.
+    // Empty bundle should return true.
-    assertFalse(spyFlutterActivity.shouldHandleDeeplinking());
+    assertTrue(spyFlutterActivity.shouldHandleDeeplinking());
   }
 
   @Test

engine/src/flutter/shell/platform/android/test/io/flutter/embedding/android/FlutterFragmentActivityTest.java

@@ -180,8 +180,8 @@ public class FlutterFragmentActivityTest {
     Bundle bundle = new Bundle();
     FlutterFragmentActivity spyFlutterActivity = spy(activity);
     when(spyFlutterActivity.getMetaData()).thenReturn(bundle);
-    // Empty bundle should return false.
+    // Empty bundle should return true.
-    assertFalse(spyFlutterActivity.shouldHandleDeeplinking());
+    assertTrue(spyFlutterActivity.shouldHandleDeeplinking());
   }
 
   @Test

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterAppDelegate.mm

@@ -137,8 +137,8 @@ static NSString* const kRestorationStateAppModificationKey = @"mod-date";
 - (BOOL)isFlutterDeepLinkingEnabled {
   NSNumber* isDeepLinkingEnabled =
       [[NSBundle mainBundle] objectForInfoDictionaryKey:@"FlutterDeepLinkingEnabled"];
-  // if not set, return NO
+  // if not set, return YES
-  return isDeepLinkingEnabled ? [isDeepLinkingEnabled boolValue] : NO;
+  return isDeepLinkingEnabled ? [isDeepLinkingEnabled boolValue] : YES;
 }
 
 // This method is called when opening an URL with custom schemes.

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterAppDelegateTest.mm

@@ -80,12 +80,18 @@ FLUTTER_ASSERT_ARC
   OCMStub([self.mockMainBundle objectForInfoDictionaryKey:@"FlutterDeepLinkingEnabled"])
       .andReturn(nil);
 
+  OCMStub([self.mockNavigationChannel
+              invokeMethod:@"pushRouteInformation"
+                 arguments:@{@"location" : @"http://myApp/custom/route?query=test"}])
+      .andReturn(@YES);
+
   BOOL result =
       [self.appDelegate application:[UIApplication sharedApplication]
                             openURL:[NSURL URLWithString:@"http://myApp/custom/route?query=test"]
                             options:@{}];
-  XCTAssertFalse(result);
+
-  OCMReject([self.mockNavigationChannel invokeMethod:OCMOCK_ANY arguments:OCMOCK_ANY]);
+  XCTAssertTrue(result);
+  OCMVerifyAll(self.mockNavigationChannel);
 }
 
 - (void)testLaunchUrlWithDeepLinkingDisabled {