[flutter_tool] Throw tool exit on malformed storage url override (#38637)

packages/flutter_tools/lib/src/base/net.dart

@@ -8,6 +8,7 @@ import '../base/context.dart';
 import '../globals.dart';
 import 'common.dart';
 import 'io.dart';
+import 'platform.dart';
 
 const int kNetworkProblemExitCode = 50;
 
@@ -53,6 +54,19 @@ Future<List<int>> _attempt(Uri url, { bool onlyHeaders = false }) async {
     } else {
       request = await httpClient.getUrl(url);
     }
+  } on ArgumentError catch (error) {
+    final String overrideUrl = platform.environment['FLUTTER_STORAGE_BASE_URL'];
+    if (overrideUrl != null && url.toString().contains(overrideUrl)) {
+      printError(error.toString());
+      throwToolExit(
+        'The value of FLUTTER_STORAGE_BASE_URL ($overrideUrl) could not be '
+        'parsed as a valid url. Please see https://flutter.dev/community/china '
+        'for an example of how to use it.\n'
+        'Full URL: $url',
+        exitCode: kNetworkProblemExitCode,);
+    }
+    printError(error.toString());
+    rethrow;
   } on HandshakeException catch (error) {
     printTrace(error.toString());
     throwToolExit(

packages/flutter_tools/test/general.shard/base/net_test.dart

@@ -7,6 +7,7 @@ import 'dart:typed_data';
 
 import 'package:flutter_tools/src/base/io.dart' as io;
 import 'package:flutter_tools/src/base/net.dart';
+import 'package:flutter_tools/src/base/platform.dart';
 import 'package:quiver/testing/async.dart';
 
 import '../../src/common.dart';
@@ -105,7 +106,32 @@ void main() {
     ),
   });
 
-testUsingContext('retry from HttpException', () async {
+  testUsingContext('check for bad override on ArgumentError', () async {
+    String error;
+    FakeAsync().run((FakeAsync time) {
+      fetchUrl(Uri.parse('example.invalid/')).then((List<int> value) {
+        error = 'test completed unexpectedly';
+      }, onError: (dynamic exception) {
+        error = 'test failed: $exception';
+      });
+      expect(testLogger.statusText, '');
+      time.elapse(const Duration(milliseconds: 10000));
+      expect(testLogger.statusText, '');
+    });
+    expect(error, startsWith('test failed'));
+    expect(testLogger.errorText, contains('Invalid argument'));
+    expect(error, contains('FLUTTER_STORAGE_BASE_URL'));
+  }, overrides: <Type, Generator>{
+    HttpClientFactory: () => () => MockHttpClientThrowing(
+      ArgumentError('test exception handling'),
+    ),
+    Platform: () => FakePlatform.fromPlatform(const LocalPlatform())
+      ..environment = <String, String>{
+        'FLUTTER_STORAGE_BASE_URL': 'example.invalid'
+      },
+  });
+
+  testUsingContext('retry from HttpException', () async {
     String error;
     FakeAsync().run((FakeAsync time) {
       fetchUrl(Uri.parse('http://example.invalid/')).then((List<int> value) {
@@ -183,7 +209,7 @@ testUsingContext('retry from HttpException', () async {
 class MockHttpClientThrowing implements io.HttpClient {
   MockHttpClientThrowing(this.exception);
 
-  final Exception exception;
+  final Object exception;
 
   @override
   Future<io.HttpClientRequest> getUrl(Uri url) async {