Provide asset lookup key on ios (#4817)

shell/platform/darwin/ios/framework/Headers/FlutterDartProject.h

@@ -23,6 +23,26 @@ FLUTTER_EXPORT
 
 - (instancetype)initFromDefaultSourceForConfiguration;
 
+/**
+ Returns the file name for the given asset.
+ The returned file name can be used to access the asset in the application's main bundle.
+
+ - Parameter asset: The name of the asset. The name can be hierarchical.
+ - Returns: the file name to be used for lookup in the main bundle.
+ */
++ (NSString*)lookupKeyForAsset:(NSString*)asset;
+
+/**
+ Returns the file name for the given asset which originates from the specified package.
+ The returned file name can be used to access the asset in the application's main bundle.
+
+ - Parameters:
+   - asset: The name of the asset. The name can be hierarchical.
+   - package: The name of the package from which the asset originates.
+ - Returns: the file name to be used for lookup in the main bundle.
+ */
++ (NSString*)lookupKeyForAsset:(NSString*)asset fromPackage:(NSString*)package;
+
 @end
 
 #endif  // FLUTTER_FLUTTERDARTPROJECT_H_

shell/platform/darwin/ios/framework/Headers/FlutterPlugin.h

@@ -183,6 +183,26 @@ NS_ASSUME_NONNULL_BEGIN
  - Parameters delegate: The receiving object, such as the plugin's main class.
  */
 - (void)addApplicationDelegate:(NSObject<FlutterPlugin>*)delegate;
+
+/**
+ Returns the file name for the given asset.
+ The returned file name can be used to access the asset in the application's main bundle.
+
+ - Parameter asset: The name of the asset. The name can be hierarchical.
+ - Returns: the file name to be used for lookup in the main bundle.
+ */
+- (NSString*)lookupKeyForAsset:(NSString*)asset;
+
+/**
+ Returns the file name for the given asset which originates from the specified package.
+ The returned file name can be used to access the asset in the application's main bundle.
+
+ - Parameters:
+   - asset: The name of the asset. The name can be hierarchical.
+   - package: The name of the package from which the asset originates.
+ - Returns: the file name to be used for lookup in the main bundle.
+ */
+- (NSString*)lookupKeyForAsset:(NSString*)asset fromPackage:(NSString*)package;
 @end
 
 /**

shell/platform/darwin/ios/framework/Headers/FlutterViewController.h

@@ -22,6 +22,26 @@ FLUTTER_EXPORT
 
 - (void)handleStatusBarTouches:(UIEvent*)event;
 
+/**
+ Returns the file name for the given asset.
+ The returned file name can be used to access the asset in the application's main bundle.
+
+ - Parameter asset: The name of the asset. The name can be hierarchical.
+ - Returns: the file name to be used for lookup in the main bundle.
+ */
+- (NSString*)lookupKeyForAsset:(NSString*)asset;
+
+/**
+ Returns the file name for the given asset which originates from the specified package.
+ The returned file name can be used to access the asset in the application's main bundle.
+
+ - Parameters:
+   - asset: The name of the asset. The name can be hierarchical.
+   - package: The name of the package from which the asset originates.
+ - Returns: the file name to be used for lookup in the main bundle.
+ */
+- (NSString*)lookupKeyForAsset:(NSString*)asset fromPackage:(NSString*)package;
+
 /**
  Sets the first route that the Flutter app shows. The default is "/".
 

shell/platform/darwin/ios/framework/Source/FlutterAppDelegate.mm

@@ -284,4 +284,13 @@
 - (void)addApplicationDelegate:(NSObject<FlutterPlugin>*)delegate {
   [_appDelegate.pluginDelegates addObject:delegate];
 }
+
+- (NSString*)lookupKeyForAsset:(NSString*)asset {
+   return [FlutterDartProject lookupKeyForAsset:asset];
+}
+
+- (NSString*)lookupKeyForAsset:(NSString*)asset fromPackage:(NSString*)package {
+   return [FlutterDartProject lookupKeyForAsset:asset fromPackage:package];
+}
+
 @end

shell/platform/darwin/ios/framework/Source/FlutterDartProject.mm

@@ -146,16 +146,29 @@ static NSURL* URLForSwitch(const fxl::StringView name) {
 
 #pragma mark - Assets-related utilities
 
-+ (NSString*)pathForFlutterAssetsFromBundle:(NSBundle*)bundle {
++ (NSString*)flutterAssetsName:(NSBundle*)bundle {
   NSString* flutterAssetsName = [bundle objectForInfoDictionaryKey:@"FLTAssetsPath"];
   if (flutterAssetsName == nil) {
     // Default to "flutter_assets"
     flutterAssetsName = @"flutter_assets";
   }
+  return flutterAssetsName;
+}
 
++ (NSString*)pathForFlutterAssetsFromBundle:(NSBundle*)bundle {
+  NSString* flutterAssetsName = [FlutterDartProject flutterAssetsName:bundle];
   return [bundle pathForResource:flutterAssetsName ofType:nil];
 }
 
++ (NSString*)lookupKeyForAsset:(NSString*)asset {
+  NSString* flutterAssetsName = [FlutterDartProject flutterAssetsName: [NSBundle mainBundle]];
+  return [NSString stringWithFormat:@"%@/%@", flutterAssetsName, asset];
+}
+
++ (NSString*)lookupKeyForAsset:(NSString*)asset fromPackage:(NSString*)package {
+  return [self lookupKeyForAsset:[NSString stringWithFormat:@"packages/%@/%@", package, asset]];
+}
+
 #pragma mark - Launching the project in a preconfigured engine.
 
 static NSString* NSStringFromVMType(VMType type) {

shell/platform/darwin/ios/framework/Source/FlutterViewController.mm

@@ -908,4 +908,13 @@ constexpr CGFloat kStandardStatusBarHeight = 20.0;
 - (void)textureFrameAvailable:(int64_t)textureId {
   _platformView->MarkTextureFrameAvailable(textureId);
 }
+
+- (NSString*)lookupKeyForAsset:(NSString*)asset {
+   return [FlutterDartProject lookupKeyForAsset:asset];
+}
+
+- (NSString*)lookupKeyForAsset:(NSString*)asset fromPackage:(NSString*)package {
+   return [FlutterDartProject lookupKeyForAsset:asset fromPackage:package];
+}
+
 @end