Prompt a solution message when flutter tools network fail in China (#16244)

bin/internal/update_dart_sdk.sh

@@ -51,7 +51,15 @@ if [ ! -f "$ENGINE_STAMP" ] || [ "$ENGINE_VERSION" != `cat "$ENGINE_STAMP"` ]; t
   mkdir -p -- "$DART_SDK_PATH"
   DART_SDK_ZIP="$FLUTTER_ROOT/bin/cache/$DART_ZIP_NAME"
 
-  curl --continue-at - --location --output "$DART_SDK_ZIP" "$DART_SDK_URL" 2>&1
+  curl --continue-at - --location --output "$DART_SDK_ZIP" "$DART_SDK_URL" 2>&1 || {
+    echo
+    echo "Failed to retrieve the Dart SDK at $DART_SDK_URL"
+    echo "If you're located in China, please follow"
+    echo "https://github.com/flutter/flutter/wiki/Using-Flutter-in-China"
+    echo
+    rm -f -- "$DART_SDK_ZIP"
+    exit 1
+  }
   unzip -o -q "$DART_SDK_ZIP" -d "$FLUTTER_ROOT/bin/cache" || {
     echo
     echo "It appears that the downloaded file is corrupt; please try the operation again later."

packages/flutter_tools/lib/src/cache.dart

@@ -8,6 +8,7 @@ import 'package:meta/meta.dart';
 
 import 'base/context.dart';
 import 'base/file_system.dart';
+import 'base/io.dart' show SocketException;
 import 'base/logger.dart';
 import 'base/net.dart';
 import 'base/os.dart';
@@ -28,6 +29,10 @@ class Cache {
     }
   }
 
+  static const List<String> _hostsBlockedInChina = const <String> [
+    'storage.googleapis.com',
+  ];
+
   final Directory _rootOverride;
   final List<CachedArtifact> _artifacts = <CachedArtifact>[];
 
@@ -190,9 +195,21 @@ class Cache {
   Future<Null> updateAll() async {
     if (!_lockEnabled)
       return null;
-    for (CachedArtifact artifact in _artifacts) {
-      if (!artifact.isUpToDate())
-        await artifact.update();
+    try {
+      for (CachedArtifact artifact in _artifacts) {
+        if (!artifact.isUpToDate())
+          await artifact.update();
+      }
+    } on SocketException catch (e) {
+      if (_hostsBlockedInChina.contains(e.address?.host)) {
+        printError(
+          'Failed to retrieve Flutter tool depedencies: ${e.message}.\n'
+          "If you're in China, please follow "
+          'https://github.com/flutter/flutter/wiki/Using-Flutter-in-China',
+          emphasis: true,
+        );
+      }
+      rethrow;
     }
   }
 }

packages/flutter_tools/test/cache_test.dart

@@ -11,6 +11,7 @@ import 'package:test/test.dart';
 import 'package:platform/platform.dart';
 
 import 'package:flutter_tools/src/cache.dart';
+import 'package:flutter_tools/src/base/io.dart' show InternetAddress, SocketException;
 
 import 'src/context.dart';
 
@@ -76,6 +77,31 @@ void main() {
       verifyNever(artifact1.update());
       verify(artifact2.update());
     });
+    testUsingContext('failed storage.googleapis.com download shows China warning', () async {
+      final CachedArtifact artifact1 = new MockCachedArtifact();
+      final CachedArtifact artifact2 = new MockCachedArtifact();
+      when(artifact1.isUpToDate()).thenReturn(false);
+      when(artifact2.isUpToDate()).thenReturn(false);
+      final MockInternetAddress address = new MockInternetAddress();
+      when(address.host).thenReturn('storage.googleapis.com');
+      when(artifact1.update()).thenThrow(new SocketException(
+        'Connection reset by peer',
+        address: address,
+      ));
+      final Cache cache = new Cache(artifacts: <CachedArtifact>[artifact1, artifact2]);
+      try {
+        await cache.updateAll();
+        fail('Mock thrown exception expected');
+      } catch (e) {
+        verify(artifact1.update());
+        // Don't continue when retrieval fails.
+        verifyNever(artifact2.update());
+        expect(
+          testLogger.errorText,
+          contains('https://github.com/flutter/flutter/wiki/Using-Flutter-in-China'),
+        );
+      }
+    });
   });
 
   testUsingContext('flattenNameSubdirs', () {
@@ -103,3 +129,4 @@ class MockFile extends Mock implements File {
 
 class MockRandomAccessFile extends Mock implements RandomAccessFile {}
 class MockCachedArtifact extends Mock implements CachedArtifact {}
+class MockInternetAddress extends Mock implements InternetAddress {}