From 4ce2a7aa6d315e4ae7ae2f15dd2aafaea3d48428 Mon Sep 17 00:00:00 2001
From: Jonah Williams <jonahwilliams@google.com>
Date: Mon, 5 Oct 2020 09:05:41 -0700
Subject: [PATCH] [flutter_tools] do not use IOSink for writing cache responses
 (#67231)

Any File-derived IOSink may throw un-handleable async exceptions into the zone, see dart-lang/sdk#43663 . Instead, just write to a file with an append mode.
---
 packages/flutter_tools/lib/src/cache.dart         | 15 +++++++++------
 .../test/general.shard/artifact_updater_test.dart |  3 ++-
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/packages/flutter_tools/lib/src/cache.dart b/packages/flutter_tools/lib/src/cache.dart
index dff213da72..196b5dbe07 100644
--- a/packages/flutter_tools/lib/src/cache.dart
+++ b/packages/flutter_tools/lib/src/cache.dart
@@ -1598,10 +1598,11 @@ class ArtifactUpdater {
       );
       try {
         _ensureExists(tempFile.parent);
-        final IOSink ioSink = tempFile.openWrite();
-        await _download(url, ioSink);
-        await ioSink.flush();
-        await ioSink.close();
+        if (tempFile.existsSync()) {
+          tempFile.deleteSync();
+        }
+        await _download(url, tempFile);
+
         if (!tempFile.existsSync()) {
           throw Exception('Did not find downloaded file ${tempFile.path}');
         }
@@ -1656,13 +1657,15 @@ class ArtifactUpdater {
   }
 
   /// Download bytes from [url], throwing non-200 responses as an exception.
-  Future<void> _download(Uri url, IOSink ioSink) async {
+  Future<void> _download(Uri url, File file) async {
     final HttpClientRequest request = await _httpClient.getUrl(url);
     final HttpClientResponse response = await request.close();
     if (response.statusCode != HttpStatus.ok) {
       throw Exception(response.statusCode);
     }
-    await response.forEach(ioSink.add);
+    await response.forEach((List<int> chunk) {
+      file.writeAsBytesSync(chunk, mode: FileMode.append);
+    });
   }
 
   /// Create a temporary file and invoke [onTemporaryFile] with the file as
diff --git a/packages/flutter_tools/test/general.shard/artifact_updater_test.dart b/packages/flutter_tools/test/general.shard/artifact_updater_test.dart
index d96a6d72bd..f5741fed72 100644
--- a/packages/flutter_tools/test/general.shard/artifact_updater_test.dart
+++ b/packages/flutter_tools/test/general.shard/artifact_updater_test.dart
@@ -18,7 +18,7 @@ import 'package:mockito/mockito.dart';
 import '../src/common.dart';
 import '../src/mocks.dart';
 
-final Platform testPlatform = FakePlatform(environment: <String, String>{});
+final Platform testPlatform = FakePlatform(environment: const <String, String>{});
 
 void main() {
   testWithoutContext('ArtifactUpdater can download a zip archive', () async {
@@ -367,6 +367,7 @@ class MockHttpClientResponse extends Mock implements HttpClientResponse {
 
   @override
   Future<void> forEach(void Function(List<int> element) action) async {
+    action(<int>[0]);
     return;
   }
 }