Fix asset bundle

flutter/lib/src/sentry_asset_bundle.dart

@@ -1,4 +1,6 @@
 import 'dart:async';
+import 'dart:typed_data';
+import 'dart:ui';
 
 import 'package:flutter/services.dart';
 import 'package:flutter/material.dart';
@@ -143,6 +145,8 @@ class SentryAssetBundle implements AssetBundle {
       byteLength = data.length;
     } else if (data is ByteData) {
       byteLength = data.lengthInBytes;
+    } else if (data is ImmutableBuffer) {
+      byteLength = data.length;
     }
     if (byteLength != null) {
       span?.setData('file.size', byteLength);
@@ -177,6 +181,49 @@ class SentryAssetBundle implements AssetBundle {
     }
   }
 
+  @override
+  // This is an override on Flutter 3.1 (I guess) and later
+  // ignore: override_on_non_overriding_member
+  Future<ImmutableBuffer> loadBuffer(String key) async {
+    final span = _hub.getSpan()?.startChild(
+          'file.read',
+          description: 'AssetBundle.loadBuffer: ${_fileName(key)}',
+        );
+
+    span?.setData('file.path', key);
+
+    ImmutableBuffer data;
+    try {
+      data = await _loadBuffer(key);
+      _setDataLength(data, span);
+      span?.status = SpanStatus.ok();
+    } catch (exception) {
+      span?.throwable = exception;
+      span?.status = SpanStatus.internalError();
+      rethrow;
+    } finally {
+      await span?.finish();
+    }
+    return data;
+  }
+
+  Future<ImmutableBuffer> _loadBuffer(String key) async {
+    try {
+      return (_bundle as dynamic).loadBuffer(key);
+    } on NoSuchMethodError catch (_) {
+      // The loadBuffer method exists as of Flutter 3.1
+      // Previous versions don't have it, but later versions do.
+      // We can't use `extends` in order to provide this method because this is
+      // a wrapper and thus the method call must be forwarded.
+      // On Flutter versions <=3.1 we can't forward this call and
+      // just catch the error which is thrown. On later version the call gets
+      // correctly forwarded.
+      //
+      // In case of a NoSuchMethodError we just return an empty list
+      return ImmutableBuffer.fromUint8List(Uint8List.fromList([]));
+    }
+  }
+
   static Future<T> _wrapParsing<T>(
     _Parser<T> parser,
     String value,

flutter/test/sentry_asset_bundle_test.dart

@@ -2,6 +2,7 @@
 // The lint above is okay, because we're using another Sentry package
 import 'dart:convert';
 import 'dart:typed_data';
+import 'dart:ui';
 
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -137,6 +138,53 @@ void main() {
       expect(span.context.description, 'AssetBundle.loadString: test.txt');
     });
 
+    test('loadBuffer: creates a span if transaction is bound to scope',
+        () async {
+      final sut = fixture.getSut();
+      final tr = fixture._hub.startTransaction(
+        'name',
+        'op',
+        bindToScope: true,
+      );
+
+      await sut.loadBuffer(_testFileName);
+
+      await tr.finish();
+
+      final tracer = (tr as SentryTracer);
+      final span = tracer.children.first;
+
+      expect(span.status, SpanStatus.ok());
+      expect(span.finished, true);
+      expect(span.context.operation, 'file.read');
+      expect(span.data['file.path'], 'resources/test.txt');
+      expect(span.data['file.size'], 12);
+      expect(span.context.description, 'AssetBundle.loadBuffer: test.txt');
+    });
+
+    test('loadBuffer: end span with error if exception is thrown', () async {
+      final sut = fixture.getSut(throwException: true);
+      final tr = fixture._hub.startTransaction(
+        'name',
+        'op',
+        bindToScope: true,
+      );
+
+      try {
+        await sut.loadBuffer(_testFileName);
+      } catch (_) {}
+
+      await tr.finish();
+
+      final tracer = (tr as SentryTracer);
+      final span = tracer.children.first;
+
+      expect(span.status, SpanStatus.internalError());
+      expect(span.finished, true);
+      expect(span.context.operation, 'file.read');
+      expect(span.context.description, 'AssetBundle.loadBuffer: test.txt');
+    });
+
     test(
       'loadStructuredData: does not create any spans and just forwords the call to the underlying assetbundle if disabled',
       () async {
@@ -359,4 +407,18 @@ class TestAssetBundle extends CachingAssetBundle {
     super.evict(key);
     evictKey = key;
   }
+
+  @override
+  // This is an override on Flutter 3.1 (I guess) and later
+  // ignore: override_on_non_overriding_member
+  Future<ImmutableBuffer> loadBuffer(String key) async {
+    if (throwException) {
+      throw Exception('exception thrown for testing purposes');
+    }
+    if (key == _testFileName) {
+      return ImmutableBuffer.fromUint8List(
+          Uint8List.fromList(utf8.encode('Hello World!')));
+    }
+    return ImmutableBuffer.fromUint8List(Uint8List.fromList([]));
+  }
 }