[flutter_tools] add a mechanism to turn off immediate tool exit (#66787)

Instead of always exiting the tool, provide a mechanism to turn off this behavior for non-critical functionality like configuration and analytics settings.

Fixes #66786 Fixes #4674

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

@@ -5,6 +5,7 @@
 import 'package:meta/meta.dart';
 
 import '../convert.dart';
+import 'error_handling_io.dart';
 import 'file_system.dart';
 import 'logger.dart';
 import 'platform.dart';
@@ -25,7 +26,7 @@ class Config {
       _userHomePath(platform),
       name,
     ));
-    return Config._(file, logger);
+    return Config.createForTesting(file, logger);
   }
 
   /// Constructs a new [Config] object from a file called [name] in
@@ -34,14 +35,18 @@ class Config {
     String name, {
     @required Directory directory,
     @required Logger logger,
-  }) => Config._(directory.childFile(name), logger);
+  }) => Config.createForTesting(directory.childFile(name), logger);
 
-  Config._(File file, Logger logger) : _file = file, _logger = logger {
+  /// Test only access to the Config constructor.
+  @visibleForTesting
+  Config.createForTesting(File file, Logger logger) : _file = file, _logger = logger {
     if (!_file.existsSync()) {
       return;
     }
     try {
-      _values = castStringKeyedMap(json.decode(_file.readAsStringSync()));
+      ErrorHandlingFileSystem.noExitOnFailure(() {
+        _values = castStringKeyedMap(json.decode(_file.readAsStringSync()));
+      });
     } on FormatException {
       _logger
         ..printError('Failed to decode preferences in ${_file.path}.')
@@ -50,6 +55,13 @@ class Config {
             'with the "flutter config" command.',
         );
       _file.deleteSync();
+    } on Exception catch (err) {
+      _logger
+        ..printError('Could not read preferences in ${file.path}.\n$err')
+        ..printError(
+            'You may need to resolve the error above and reapply any previously '
+            'saved configuration with the "flutter config" command.',
+        );
     }
   }
 

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

@@ -45,6 +45,26 @@ class ErrorHandlingFileSystem extends ForwardingFileSystem {
 
   final Platform _platform;
 
+  /// Allow any file system operations executed within the closure to fail with any
+  /// operating system error, rethrowing an [Exception] instead of a [ToolExit].
+  ///
+  /// This should not be used with async file system operation.
+  ///
+  /// This can be used to bypass the [ErrorHandlingFileSystem] permission exit
+  /// checks for situations where failure is acceptable, such as the flutter
+  /// persistent settings cache.
+  static void noExitOnFailure(void Function() operation) {
+    final bool previousValue = ErrorHandlingFileSystem._noExitOnFailure;
+    try {
+      ErrorHandlingFileSystem._noExitOnFailure = true;
+      operation();
+    } finally {
+      ErrorHandlingFileSystem._noExitOnFailure = previousValue;
+    }
+  }
+
+  static bool _noExitOnFailure = false;
+
   @override
   Directory get currentDirectory => directory(delegate.currentDirectory);
 
@@ -147,6 +167,15 @@ class ErrorHandlingFile
     );
   }
 
+  @override
+  String readAsStringSync({Encoding encoding = utf8}) {
+    return _runSync<String>(
+      () => delegate.readAsStringSync(),
+      platform: _platform,
+      failureMessage: 'Flutter failed to read a file at "${delegate.path}"',
+    );
+  }
+
   @override
   void writeAsBytesSync(
     List<int> bytes, {
@@ -542,26 +571,26 @@ void _handlePosixException(Exception e, String message, int errorCode) {
   const int enospc = 28;
   const int eacces = 13;
   // Catch errors and bail when:
+  String errorMessage;
   switch (errorCode) {
     case enospc:
-      throwToolExit(
+      errorMessage =
         '$message. The target device is full.'
         '\n$e\n'
-        'Free up space and try again.',
-      );
+        'Free up space and try again.';
       break;
     case eperm:
     case eacces:
-      throwToolExit(
+      errorMessage =
         '$message. The flutter tool cannot access the file or directory.\n'
         'Please ensure that the SDK and/or project is installed in a location '
-        'that has read/write permissions for the current user.'
-      );
+        'that has read/write permissions for the current user.';
       break;
     default:
       // Caller must rethrow the exception.
       break;
   }
+  _throwFileSystemException(errorMessage);
 }
 
 void _handleWindowsException(Exception e, String message, int errorCode) {
@@ -571,31 +600,40 @@ void _handleWindowsException(Exception e, String message, int errorCode) {
   const int kUserMappedSectionOpened = 1224;
   const int kAccessDenied = 5;
   // Catch errors and bail when:
+  String errorMessage;
   switch (errorCode) {
     case kAccessDenied:
-      throwToolExit(
+      errorMessage =
         '$message. The flutter tool cannot access the file.\n'
         'Please ensure that the SDK and/or project is installed in a location '
-        'that has read/write permissions for the current user.'
-      );
+        'that has read/write permissions for the current user.';
       break;
     case kDeviceFull:
-      throwToolExit(
+      errorMessage =
         '$message. The target device is full.'
         '\n$e\n'
-        'Free up space and try again.',
-      );
+        'Free up space and try again.';
       break;
     case kUserMappedSectionOpened:
-      throwToolExit(
+      errorMessage =
         '$message. The file is being used by another program.'
         '\n$e\n'
         'Do you have an antivirus program running? '
-        'Try disabling your antivirus program and try again.',
-      );
+        'Try disabling your antivirus program and try again.';
       break;
     default:
       // Caller must rethrow the exception.
       break;
   }
+  _throwFileSystemException(errorMessage);
+}
+
+void _throwFileSystemException(String errorMessage) {
+  if (errorMessage == null) {
+    return;
+  }
+  if (ErrorHandlingFileSystem._noExitOnFailure) {
+    throw Exception(errorMessage);
+  }
+  throwToolExit(errorMessage);
 }

packages/flutter_tools/lib/src/convert.dart

@@ -7,9 +7,19 @@
 import 'dart:convert' hide utf8;
 import 'dart:convert' as cnv show utf8, Utf8Decoder;
 
+import 'package:meta/meta.dart';
+
 import 'base/common.dart';
 export 'dart:convert' hide utf8, Utf8Codec, Utf8Decoder;
 
+/// The original utf8 encoding for testing overrides only.
+///
+/// Attempting to use the flutter tool utf8 decoder will surface an analyzer
+/// warning that overrides cannot change the default value of a named
+/// parameter.
+@visibleForTesting
+const Encoding utf8ForTesting = cnv.utf8;
+
 /// A [Codec] which reports malformed bytes when decoding.
 ///
 /// Occasionally people end up in a situation where we try to decode bytes

packages/flutter_tools/lib/src/reporting/reporting.dart

@@ -12,6 +12,7 @@ import 'package:intl/intl.dart';
 import 'package:meta/meta.dart';
 import 'package:usage/usage_io.dart';
 
+import '../base/error_handling_io.dart';
 import '../base/file_system.dart';
 import '../base/io.dart';
 import '../base/logger.dart';

packages/flutter_tools/lib/src/reporting/usage.dart

@@ -221,14 +221,16 @@ class _DefaultUsage implements Usage {
       _analytics = LogToFileAnalytics(logFilePath);
     } else {
       try {
-        _analytics = analyticsIOFactory(
-          _kFlutterUA,
-          settingsName,
-          version,
-          documentDirectory: configDirOverride != null
-            ? globals.fs.directory(configDirOverride)
-            : null,
-        );
+        ErrorHandlingFileSystem.noExitOnFailure(() {
+          _analytics = analyticsIOFactory(
+            _kFlutterUA,
+            settingsName,
+            version,
+            documentDirectory: configDirOverride != null
+              ? globals.fs.directory(configDirOverride)
+              : null,
+          );
+        });
       } on Exception catch (e) {
         globals.printTrace('Failed to initialize analytics reporting: $e');
         suppressAnalytics = true;

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

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'package:file/file.dart';
+import 'package:flutter_tools/src/base/common.dart';
 import 'package:flutter_tools/src/base/error_handling_io.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/io.dart';
@@ -71,6 +72,18 @@ void setupWriteMocks({
   )).thenThrow(FileSystemException('', '', OSError('', errorCode)));
 }
 
+void setupReadMocks({
+  FileSystem mockFileSystem,
+  ErrorHandlingFileSystem fs,
+  int errorCode,
+}) {
+  final MockFile mockFile = MockFile();
+  when(mockFileSystem.file(any)).thenReturn(mockFile);
+  when(mockFile.readAsStringSync(
+    encoding: anyNamed('encoding'),
+  )).thenThrow(FileSystemException('', '', OSError('', errorCode)));
+}
+
 void setupDirectoryMocks({
   FileSystem mockFileSystem,
   ErrorHandlingFileSystem fs,
@@ -114,6 +127,30 @@ void main() {
       when(mockFileSystem.path).thenReturn(MockPathContext());
     });
 
+    testWithoutContext('bypasses error handling when withAllowedFailure is used', () {
+      setupWriteMocks(
+        mockFileSystem: mockFileSystem,
+        fs: fs,
+        errorCode: kUserPermissionDenied,
+      );
+
+      final File file = fs.file('file');
+
+      expect(() => ErrorHandlingFileSystem.noExitOnFailure(
+        () => file.writeAsStringSync('')), throwsA(isA<Exception>()));
+
+      // nesting does not unconditionally re-enable errors.
+      expect(() {
+        ErrorHandlingFileSystem.noExitOnFailure(() {
+          ErrorHandlingFileSystem.noExitOnFailure(() { });
+          file.writeAsStringSync('');
+        });
+      }, throwsA(isA<Exception>()));
+
+      // Check that state does not leak.
+      expect(() => file.writeAsStringSync(''), throwsA(isA<ToolExit>()));
+    });
+
     testWithoutContext('when access is denied', () async {
       setupWriteMocks(
         mockFileSystem: mockFileSystem,
@@ -219,6 +256,20 @@ void main() {
       expect(() => directory.existsSync(),
              throwsToolExit(message: expectedMessage));
     });
+
+    testWithoutContext('When reading from a file without permission', () {
+      setupReadMocks(
+        mockFileSystem: mockFileSystem,
+        fs: fs,
+        errorCode: kUserPermissionDenied,
+      );
+
+      final File file = fs.file('file');
+
+      const String expectedMessage = 'Flutter failed to read a file at';
+      expect(() => file.readAsStringSync(),
+             throwsToolExit(message: expectedMessage));
+    });
   });
 
   group('throws ToolExit on Linux', () {
@@ -437,6 +488,20 @@ void main() {
       expect(() => directory.existsSync(),
              throwsToolExit(message: expectedMessage));
     });
+
+    testWithoutContext('When reading from a file without permission', () {
+      setupReadMocks(
+        mockFileSystem: mockFileSystem,
+        fs: fs,
+        errorCode: eacces,
+      );
+
+      final File file = fs.file('file');
+
+      const String expectedMessage = 'Flutter failed to read a file at';
+      expect(() => file.readAsStringSync(),
+             throwsToolExit(message: expectedMessage));
+    });
   });
 
   testWithoutContext('Caches path context correctly', () {

packages/flutter_tools/test/general.shard/config_test.dart

@@ -4,10 +4,12 @@
 
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/base/config.dart';
+import 'package:flutter_tools/src/base/error_handling_io.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/logger.dart';
 import 'package:flutter_tools/src/base/platform.dart';
-import 'package:flutter_tools/src/base/terminal.dart';
+import 'package:flutter_tools/src/convert.dart';
+import 'package:test/fake.dart';
 
 import '../src/common.dart';
 
@@ -62,13 +64,7 @@ void main() {
   });
 
   testWithoutContext('Config parse error', () {
-    final BufferLogger bufferLogger = BufferLogger(
-      terminal: AnsiTerminal(
-        stdio: null,
-        platform: const LocalPlatform(),
-      ),
-      outputPreferences: OutputPreferences.test(),
-    );
+    final BufferLogger bufferLogger = BufferLogger.test();
     final File file = memoryFileSystem.file('example')
       ..writeAsStringSync('{"hello":"bar');
     config = Config(
@@ -81,4 +77,50 @@ void main() {
     expect(file.existsSync(), false);
     expect(bufferLogger.errorText, contains('Failed to decode preferences'));
   });
+
+  testWithoutContext('Config does not error on missing file', () {
+    final BufferLogger bufferLogger = BufferLogger.test();
+    final File file = memoryFileSystem.file('example');
+    config = Config(
+      'example',
+      fileSystem: memoryFileSystem,
+      logger: bufferLogger,
+      platform: fakePlatform,
+    );
+
+    expect(file.existsSync(), false);
+    expect(bufferLogger.errorText, isEmpty);
+  });
+
+  testWithoutContext('Config does not error on a normally fatal file system exception', () {
+    final BufferLogger bufferLogger = BufferLogger.test();
+    final File file = ErrorHandlingFile(
+      platform: FakePlatform(operatingSystem: 'linux'),
+      fileSystem: MemoryFileSystem.test(),
+      delegate: FakeFile('testfile'),
+    );
+
+    config = Config.createForTesting(file, bufferLogger);
+
+    expect(bufferLogger.errorText, contains('Could not read preferences in testfile'));
+    // Also contains original error message:
+    expect(bufferLogger.errorText, contains('The flutter tool cannot access the file or directory'));
+  });
+}
+
+class FakeFile extends Fake implements File {
+  FakeFile(this.path);
+
+  @override
+  final String path;
+
+  @override
+  bool existsSync() {
+    return true;
+  }
+
+  @override
+  String readAsStringSync({Encoding encoding = utf8ForTesting}) {
+    throw const FileSystemException('', '', OSError('', 13)); // EACCES error on linux
+  }
 }