[iOS] fix hot restart with native assets (#148752)

Fixes flutter/flutter#148687

Adds support for running the hot restart and reload integration test on
iOS simulator.

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- [x] I updated/added relevant documentation (doc comments with `///`).
- [ ] I added new tests to check the change I am making, or this PR is
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Author: knopp

dev/devicelab/bin/tasks/native_assets_ios_simulator.dart

@@ -12,12 +12,13 @@ Future<void> main() async {
   await task(() async {
     deviceOperatingSystem = DeviceOperatingSystem.ios;
     String? simulatorDeviceId;
+    TaskResult res = TaskResult.success(null);
     try {
       await testWithNewIOSSimulator(
         'TestNativeAssetsSim',
         (String deviceId) async {
           simulatorDeviceId = deviceId;
-          await createNativeAssetsTest(
+          res = await createNativeAssetsTest(
             deviceIdOverride: deviceId,
             isIosSimulator: true,
           )();
@@ -26,6 +27,6 @@ Future<void> main() async {
     } finally {
       await removeIOSSimulator(simulatorDeviceId);
     }
-    return TaskResult.success(null);
+    return res;
   });
 }

dev/devicelab/lib/tasks/native_assets_test.dart

@@ -54,11 +54,14 @@ TaskFunction createNativeAssetsTest({
         ];
         int transitionCount = 0;
         bool done = false;
+        bool error = false;
 
         await inDirectory<void>(exampleDirectory, () async {
           final int runFlutterResult = await runFlutter(
             options: options,
             onLine: (String line, Process process) {
+              error |= line.contains('EXCEPTION CAUGHT BY WIDGETS LIBRARY');
+              error |= line.contains("Invalid argument(s): Couldn't resolve native function 'sum'");
               if (done) {
                 return;
               }
@@ -108,6 +111,9 @@ TaskFunction createNativeAssetsTest({
             '(expected $expectedNumberOfTransitions)',
           );
         }
+        if (error) {
+          return TaskResult.failure('Error during hot reload or hot restart.');
+        }
         return TaskResult.success(null);
       });
       if (buildModeResult.failed) {

packages/flutter_tools/lib/src/isolated/native_assets/ios/native_assets.dart

@@ -186,14 +186,23 @@ Map<KernelAssetPath, List<AssetImpl>> _fatAssetTargetLocations(
 Map<AssetImpl, KernelAsset> _assetTargetLocations(
     List<AssetImpl> nativeAssets) {
   final Set<String> alreadyTakenNames = <String>{};
-  return <AssetImpl, KernelAsset>{
-    for (final AssetImpl asset in nativeAssets)
-      asset: _targetLocationIOS(asset, alreadyTakenNames),
-  };
+  final Map<String, KernelAssetPath> idToPath = <String, KernelAssetPath>{};
+  final Map<AssetImpl, KernelAsset> result = <AssetImpl, KernelAsset>{};
+  for (final AssetImpl asset in nativeAssets) {
+    final KernelAssetPath path = idToPath[asset.id] ??
+        _targetLocationIOS(asset, alreadyTakenNames).path;
+    idToPath[asset.id] = path;
+    result[asset] = KernelAsset(
+      id: (asset as NativeCodeAssetImpl).id,
+      target: Target.fromArchitectureAndOS(asset.architecture!, asset.os),
+      path: path,
+    );
+  }
+  return result;
 }
 
 KernelAsset _targetLocationIOS(AssetImpl asset, Set<String> alreadyTakenNames) {
-  final LinkModeImpl linkMode = (asset as NativeCodeAssetImpl).linkMode;
+final LinkModeImpl linkMode = (asset as NativeCodeAssetImpl).linkMode;
 final KernelAssetPath kernelAssetPath;
   switch (linkMode) {
     case DynamicLoadingSystemImpl _: