From 5be462f550b5519b664037eb1b8769381db1bddb Mon Sep 17 00:00:00 2001
From: Jenn Magder <magder@google.com>
Date: Wed, 3 Nov 2021 17:36:32 -0700
Subject: [PATCH] Migrate doctor, format, and a few other commands to null
 safety (#92952)

---
 .../lib/src/commands/doctor.dart              | 15 ++++----
 .../lib/src/commands/format.dart              | 14 ++++----
 .../lib/src/commands/generate.dart            |  2 --
 .../src/commands/generate_localizations.dart  | 28 +++++++--------
 .../lib/src/commands/ide_config.dart          | 25 ++++++-------
 .../lib/src/commands/screenshot.dart          | 36 +++++++++----------
 .../lib/src/commands/shell_completion.dart    | 13 +++----
 .../lib/src/commands/symbolize.dart           | 30 ++++++++--------
 packages/flutter_tools/lib/src/template.dart  |  4 +--
 9 files changed, 72 insertions(+), 95 deletions(-)

diff --git a/packages/flutter_tools/lib/src/commands/doctor.dart b/packages/flutter_tools/lib/src/commands/doctor.dart
index c22595353f0..06de1b48784 100644
--- a/packages/flutter_tools/lib/src/commands/doctor.dart
+++ b/packages/flutter_tools/lib/src/commands/doctor.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import '../android/android_workflow.dart';
 import '../base/common.dart';
 import '../globals.dart' as globals;
@@ -12,7 +10,6 @@ import '../runner/flutter_command.dart';
 class DoctorCommand extends FlutterCommand {
   DoctorCommand({this.verbose = false}) {
     argParser.addFlag('android-licenses',
-      defaultsTo: false,
       negatable: false,
       help: "Run the Android SDK manager tool to accept the SDK's licenses.",
     );
@@ -37,11 +34,11 @@ class DoctorCommand extends FlutterCommand {
   @override
   Future<FlutterCommandResult> runCommand() async {
     globals.flutterVersion.fetchTagsAndUpdate();
-    if (argResults.wasParsed('check-for-remote-artifacts')) {
-      final String engineRevision = stringArg('check-for-remote-artifacts');
+    if (argResults?.wasParsed('check-for-remote-artifacts') == true) {
+      final String engineRevision = stringArg('check-for-remote-artifacts')!;
       if (engineRevision.startsWith(RegExp(r'[a-f0-9]{1,40}'))) {
-        final bool success = await globals.doctor.checkRemoteArtifacts(engineRevision);
-        if (!success) {
+        final bool success = await globals.doctor?.checkRemoteArtifacts(engineRevision) ?? false;
+        if (success) {
           throwToolExit('Artifacts for engine $engineRevision are missing or are '
               'not yet available.', exitCode: 1);
         }
@@ -50,11 +47,11 @@ class DoctorCommand extends FlutterCommand {
             'git hash.');
       }
     }
-    final bool success = await globals.doctor.diagnose(
+    final bool success = await globals.doctor?.diagnose(
       androidLicenses: boolArg('android-licenses'),
       verbose: verbose,
       androidLicenseValidator: androidLicenseValidator,
-    );
+    ) ?? false;
     return FlutterCommandResult(success ? ExitStatus.success : ExitStatus.warning);
   }
 }
diff --git a/packages/flutter_tools/lib/src/commands/format.dart b/packages/flutter_tools/lib/src/commands/format.dart
index 35d735f3c35..986dc7ba22b 100644
--- a/packages/flutter_tools/lib/src/commands/format.dart
+++ b/packages/flutter_tools/lib/src/commands/format.dart
@@ -2,10 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:args/args.dart';
-import 'package:meta/meta.dart';
 
 import '../artifacts.dart';
 import '../base/common.dart';
@@ -13,7 +10,7 @@ import '../globals.dart' as globals;
 import '../runner/flutter_command.dart';
 
 class FormatCommand extends FlutterCommand {
-  FormatCommand({@required this.verboseHelp});
+  FormatCommand({required this.verboseHelp});
 
   @override
   ArgParser argParser = ArgParser.allowAnything();
@@ -33,23 +30,24 @@ class FormatCommand extends FlutterCommand {
   String get category => FlutterCommandCategory.project;
 
   @override
-  String get invocation => '${runner.executableName} $name <one or more paths>';
+  String get invocation => '${runner?.executableName} $name <one or more paths>';
 
   @override
   Future<FlutterCommandResult> runCommand() async {
-    final String dartBinary = globals.artifacts.getHostArtifact(HostArtifact.engineDartBinary).path;
+    final String dartBinary = globals.artifacts!.getHostArtifact(HostArtifact.engineDartBinary).path;
     final List<String> command = <String>[
       dartBinary,
       'format',
     ];
-    if (argResults.rest.isEmpty) {
+    final List<String> rest = argResults?.rest ?? <String>[];
+    if (rest.isEmpty) {
       globals.printError(
         'No files specified to be formatted.'
       );
       command.add('-h');
     } else {
       command.addAll(<String>[
-        for (String arg in argResults.rest)
+        for (String arg in rest)
           if (arg == '--dry-run' || arg == '-n')
             '--output=none'
           else
diff --git a/packages/flutter_tools/lib/src/commands/generate.dart b/packages/flutter_tools/lib/src/commands/generate.dart
index a79aeef1045..d815d05d0e8 100644
--- a/packages/flutter_tools/lib/src/commands/generate.dart
+++ b/packages/flutter_tools/lib/src/commands/generate.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import '../globals.dart' as globals;
 import '../runner/flutter_command.dart';
 
diff --git a/packages/flutter_tools/lib/src/commands/generate_localizations.dart b/packages/flutter_tools/lib/src/commands/generate_localizations.dart
index 199825444d9..17bf0697129 100644
--- a/packages/flutter_tools/lib/src/commands/generate_localizations.dart
+++ b/packages/flutter_tools/lib/src/commands/generate_localizations.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import '../base/common.dart';
 import '../base/file_system.dart';
 import '../base/logger.dart';
@@ -21,8 +19,8 @@ import '../runner/flutter_command.dart';
 /// [internationalization user guide](flutter.dev/go/i18n-user-guide).
 class GenerateLocalizationsCommand extends FlutterCommand {
   GenerateLocalizationsCommand({
-    FileSystem fileSystem,
-    Logger logger,
+    required FileSystem fileSystem,
+    required Logger logger,
   }) :
     _fileSystem = fileSystem,
     _logger = logger {
@@ -108,7 +106,6 @@ class GenerateLocalizationsCommand extends FlutterCommand {
     );
     argParser.addFlag(
       'use-deferred-loading',
-      defaultsTo: false,
       help: 'Whether to generate the Dart localization file with locales imported '
             'as deferred, allowing for lazy loading of each locale in Flutter web.\n'
             '\n'
@@ -214,25 +211,24 @@ class GenerateLocalizationsCommand extends FlutterCommand {
         logger: _logger,
         options: options,
         projectDir: _fileSystem.currentDirectory,
-        dependenciesDir: null,
         fileSystem: _fileSystem,
       );
       return FlutterCommandResult.success();
     }
 
-    final String inputPathString = stringArg('arb-dir');
-    final String outputPathString = stringArg('output-dir');
-    final String outputFileString = stringArg('output-localization-file');
-    final String templateArbFileName = stringArg('template-arb-file');
-    final String untranslatedMessagesFile = stringArg('untranslated-messages-file');
-    final String classNameString = stringArg('output-class');
+    final String inputPathString = stringArg('arb-dir')!; // Has default value, cannot be null.
+    final String? outputPathString = stringArg('output-dir');
+    final String outputFileString = stringArg('output-localization-file')!; // Has default value, cannot be null.
+    final String templateArbFileName = stringArg('template-arb-file')!; // Has default value, cannot be null.
+    final String? untranslatedMessagesFile = stringArg('untranslated-messages-file');
+    final String classNameString = stringArg('output-class')!; // Has default value, cannot be null.
     final List<String> preferredSupportedLocales = stringsArg('preferred-supported-locales');
-    final String headerString = stringArg('header');
-    final String headerFile = stringArg('header-file');
+    final String? headerString = stringArg('header');
+    final String? headerFile = stringArg('header-file');
     final bool useDeferredLoading = boolArg('use-deferred-loading');
-    final String inputsAndOutputsListPath = stringArg('gen-inputs-and-outputs-list');
+    final String? inputsAndOutputsListPath = stringArg('gen-inputs-and-outputs-list');
     final bool useSyntheticPackage = boolArg('synthetic-package');
-    final String projectPathString = stringArg('project-dir');
+    final String? projectPathString = stringArg('project-dir');
     final bool areResourceAttributesRequired = boolArg('required-resource-attributes');
     final bool usesNullableGetter = boolArg('nullable-getter');
 
diff --git a/packages/flutter_tools/lib/src/commands/ide_config.dart b/packages/flutter_tools/lib/src/commands/ide_config.dart
index 5f40c448aea..115a47a8684 100644
--- a/packages/flutter_tools/lib/src/commands/ide_config.dart
+++ b/packages/flutter_tools/lib/src/commands/ide_config.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import '../base/common.dart';
 import '../base/file_system.dart';
 import '../cache.dart';
@@ -15,8 +13,6 @@ class IdeConfigCommand extends FlutterCommand {
   IdeConfigCommand() {
     argParser.addFlag(
       'overwrite',
-      negatable: true,
-      defaultsTo: false,
       help: 'When performing operations, overwrite existing files.',
     );
     argParser.addFlag(
@@ -31,7 +27,6 @@ class IdeConfigCommand extends FlutterCommand {
     );
     argParser.addFlag(
       'with-root-module',
-      negatable: true,
       defaultsTo: true,
       help: 'Also create module that corresponds to the root of Flutter tree. '
             'This makes the entire Flutter tree browsable and searchable in IDE. '
@@ -60,12 +55,12 @@ class IdeConfigCommand extends FlutterCommand {
   final bool hidden = true;
 
   @override
-  String get invocation => '${runner.executableName} $name';
+  String get invocation => '${runner?.executableName} $name';
 
   static const String _ideName = 'intellij';
   Directory get _templateDirectory {
     return globals.fs.directory(globals.fs.path.join(
-      Cache.flutterRoot,
+      Cache.flutterRoot!,
       'packages',
       'flutter_tools',
       'ide_templates',
@@ -75,14 +70,14 @@ class IdeConfigCommand extends FlutterCommand {
 
   Directory get _createTemplatesDirectory {
     return globals.fs.directory(globals.fs.path.join(
-      Cache.flutterRoot,
+      Cache.flutterRoot!,
       'packages',
       'flutter_tools',
       'templates',
     ));
   }
 
-  Directory get _flutterRoot => globals.fs.directory(globals.fs.path.absolute(Cache.flutterRoot));
+  Directory get _flutterRoot => globals.fs.directory(globals.fs.path.absolute(Cache.flutterRoot!));
 
   // Returns true if any entire path element is equal to dir.
   bool _hasDirectoryInPath(FileSystemEntity entity, String dir) {
@@ -213,7 +208,8 @@ class IdeConfigCommand extends FlutterCommand {
 
   @override
   Future<FlutterCommandResult> runCommand() async {
-    if (argResults.rest.isNotEmpty) {
+    final List<String> rest = argResults?.rest ?? <String>[];
+    if (rest.isNotEmpty) {
       throwToolExit('Currently, the only supported IDE is IntelliJ\n$usage', exitCode: 2);
     }
 
@@ -222,12 +218,12 @@ class IdeConfigCommand extends FlutterCommand {
       return FlutterCommandResult.success();
     }
 
-    final String flutterRoot = globals.fs.path.absolute(Cache.flutterRoot);
+    final String flutterRoot = globals.fs.path.absolute(Cache.flutterRoot!);
     final String dirPath = globals.fs.path.normalize(
-      globals.fs.directory(globals.fs.path.absolute(Cache.flutterRoot)).absolute.path,
+      globals.fs.directory(globals.fs.path.absolute(Cache.flutterRoot!)).absolute.path,
     );
 
-    final String error = _validateFlutterDir(dirPath, flutterRoot: flutterRoot);
+    final String? error = _validateFlutterDir(dirPath, flutterRoot: flutterRoot);
     if (error != null) {
       throwToolExit(error);
     }
@@ -265,7 +261,7 @@ class IdeConfigCommand extends FlutterCommand {
 
 /// Return null if the flutter root directory is a valid destination. Return a
 /// validation message if we should disallow the directory.
-String _validateFlutterDir(String dirPath, { String flutterRoot }) {
+String? _validateFlutterDir(String dirPath, { String? flutterRoot }) {
   final FileSystemEntityType type = globals.fs.typeSync(dirPath);
 
   switch (type) { // ignore: exhaustive_cases, https://github.com/dart-lang/linter/issues/3017
@@ -277,5 +273,4 @@ String _validateFlutterDir(String dirPath, { String flutterRoot }) {
     case FileSystemEntityType.notFound:
       return null;
   }
-  return null; // dead code, remove after null safety migration
 }
diff --git a/packages/flutter_tools/lib/src/commands/screenshot.dart b/packages/flutter_tools/lib/src/commands/screenshot.dart
index 195829bb888..d8069ede5c1 100644
--- a/packages/flutter_tools/lib/src/commands/screenshot.dart
+++ b/packages/flutter_tools/lib/src/commands/screenshot.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:vm_service/vm_service.dart' as vm_service;
 
 import '../base/common.dart';
@@ -67,9 +65,9 @@ class ScreenshotCommand extends FlutterCommand {
   @override
   final List<String> aliases = <String>['pic'];
 
-  Device device;
+  Device? device;
 
-  Future<void> _validateOptions(String screenshotType, String observatoryUrl) async {
+  Future<void> _validateOptions(String? screenshotType, String? observatoryUrl) async {
     switch (screenshotType) {
       case _kDeviceType:
         if (observatoryUrl != null) {
@@ -79,8 +77,8 @@ class ScreenshotCommand extends FlutterCommand {
         if (device == null) {
           throwToolExit('Must have a connected device for screenshot type $screenshotType');
         }
-        if (!device.supportsScreenshot) {
-          throwToolExit('Screenshot not supported for ${device.name}.');
+        if (!device!.supportsScreenshot) {
+          throwToolExit('Screenshot not supported for ${device!.name}.');
         }
         break;
       default:
@@ -94,15 +92,15 @@ class ScreenshotCommand extends FlutterCommand {
   }
 
   @override
-  Future<FlutterCommandResult> verifyThenRunCommand(String commandPath) async {
+  Future<FlutterCommandResult> verifyThenRunCommand(String? commandPath) async {
     await _validateOptions(stringArg(_kType), stringArg(_kObservatoryUrl));
     return super.verifyThenRunCommand(commandPath);
   }
 
   @override
   Future<FlutterCommandResult> runCommand() async {
-    File outputFile;
-    if (argResults.wasParsed(_kOut)) {
+    File? outputFile;
+    if (argResults?.wasParsed(_kOut) == true) {
       outputFile = globals.fs.file(stringArg(_kOut));
     }
 
@@ -123,24 +121,24 @@ class ScreenshotCommand extends FlutterCommand {
                    : FlutterCommandResult.fail();
   }
 
-  Future<void> runScreenshot(File outputFile) async {
+  Future<void> runScreenshot(File? outputFile) async {
     outputFile ??= globals.fsUtils.getUniqueFile(
       globals.fs.currentDirectory,
       'flutter',
       'png',
     );
     try {
-      await device.takeScreenshot(outputFile);
+      await device!.takeScreenshot(outputFile);
     } on Exception catch (error) {
       throwToolExit('Error taking screenshot: $error');
     }
     _showOutputFileInfo(outputFile);
   }
 
-  Future<bool> runSkia(File outputFile) async {
-    final Uri observatoryUrl = Uri.parse(stringArg(_kObservatoryUrl));
+  Future<bool> runSkia(File? outputFile) async {
+    final Uri observatoryUrl = Uri.parse(stringArg(_kObservatoryUrl)!);
     final FlutterVmService vmService = await connectToVmService(observatoryUrl, logger: globals.logger);
-    final vm_service.Response skp = await vmService.screenshotSkp();
+    final vm_service.Response? skp = await vmService.screenshotSkp();
     if (skp == null) {
       globals.printError(
         'The Skia picture request failed, probably because the device was '
@@ -154,17 +152,17 @@ class ScreenshotCommand extends FlutterCommand {
       'skp',
     );
     final IOSink sink = outputFile.openWrite();
-    sink.add(base64.decode(skp.json['skp'] as String));
+    sink.add(base64.decode(skp.json?['skp'] as String));
     await sink.close();
     _showOutputFileInfo(outputFile);
     _ensureOutputIsNotJsonRpcError(outputFile);
     return true;
   }
 
-  Future<bool> runRasterizer(File outputFile) async {
-    final Uri observatoryUrl = Uri.parse(stringArg(_kObservatoryUrl));
+  Future<bool> runRasterizer(File? outputFile) async {
+    final Uri observatoryUrl = Uri.parse(stringArg(_kObservatoryUrl)!);
     final FlutterVmService vmService = await connectToVmService(observatoryUrl, logger: globals.logger);
-    final vm_service.Response response = await vmService.screenshot();
+    final vm_service.Response? response = await vmService.screenshot();
     if (response == null) {
       globals.printError(
         'The screenshot request failed, probably because the device was '
@@ -178,7 +176,7 @@ class ScreenshotCommand extends FlutterCommand {
       'png',
     );
     final IOSink sink = outputFile.openWrite();
-    sink.add(base64.decode(response.json['screenshot'] as String));
+    sink.add(base64.decode(response.json?['screenshot'] as String));
     await sink.close();
     _showOutputFileInfo(outputFile);
     _ensureOutputIsNotJsonRpcError(outputFile);
diff --git a/packages/flutter_tools/lib/src/commands/shell_completion.dart b/packages/flutter_tools/lib/src/commands/shell_completion.dart
index f30cd6e092e..5fe8de30133 100644
--- a/packages/flutter_tools/lib/src/commands/shell_completion.dart
+++ b/packages/flutter_tools/lib/src/commands/shell_completion.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:completion/completion.dart';
 
 import '../base/common.dart';
@@ -15,8 +13,6 @@ class ShellCompletionCommand extends FlutterCommand {
   ShellCompletionCommand() {
     argParser.addFlag(
       'overwrite',
-      defaultsTo: false,
-      negatable: true,
       help: 'Causes the given shell completion setup script to be overwritten if it already exists.',
     );
   }
@@ -42,21 +38,22 @@ class ShellCompletionCommand extends FlutterCommand {
 
   /// Return null to disable analytics recording of the `bash-completion` command.
   @override
-  Future<String> get usagePath async => null;
+  Future<String?> get usagePath async => null;
 
   @override
   Future<FlutterCommandResult> runCommand() async {
-    if (argResults.rest.length > 1) {
+    final List<String> rest = argResults?.rest ?? <String>[];
+    if (rest.length > 1) {
       throwToolExit('Too many arguments given to bash-completion command.', exitCode: 1);
     }
 
-    if (argResults.rest.isEmpty || argResults.rest.first == '-') {
+    if (rest.isEmpty || rest.first == '-') {
       final String script = generateCompletionScript(<String>['flutter']);
       globals.stdio.stdoutWrite(script);
       return FlutterCommandResult.warning();
     }
 
-    final File outputFile = globals.fs.file(argResults.rest.first);
+    final File outputFile = globals.fs.file(rest.first);
     if (outputFile.existsSync() && !boolArg('overwrite')) {
       throwToolExit(
         'Output file ${outputFile.path} already exists, will not overwrite. '
diff --git a/packages/flutter_tools/lib/src/commands/symbolize.dart b/packages/flutter_tools/lib/src/commands/symbolize.dart
index df915b50cad..f7ab2d20ded 100644
--- a/packages/flutter_tools/lib/src/commands/symbolize.dart
+++ b/packages/flutter_tools/lib/src/commands/symbolize.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:async';
 import 'dart:typed_data';
 
@@ -24,8 +22,8 @@ import '../runner/flutter_command.dart';
 /// over stdout.
 class SymbolizeCommand extends FlutterCommand {
   SymbolizeCommand({
-    @required Stdio stdio,
-    @required FileSystem fileSystem,
+    required Stdio stdio,
+    required FileSystem fileSystem,
     DwarfSymbolizationService dwarfSymbolizationService = const DwarfSymbolizationService(),
   }) : _stdio = stdio,
        _fileSystem = fileSystem,
@@ -67,13 +65,13 @@ class SymbolizeCommand extends FlutterCommand {
 
   @override
   Future<void> validateCommand() {
-    if (!argResults.wasParsed('debug-info')) {
+    if (argResults?.wasParsed('debug-info') != true) {
       throwToolExit('"--debug-info" is required to symbolize stack traces.');
     }
-    if (!_fileSystem.isFileSync(stringArg('debug-info'))) {
+    if (!_fileSystem.isFileSync(stringArg('debug-info')!)) {
       throwToolExit('${stringArg('debug-info')} does not exist.');
     }
-    if (argResults.wasParsed('input') && !_fileSystem.isFileSync(stringArg('input'))) {
+    if (argResults?.wasParsed('input') == true && !_fileSystem.isFileSync(stringArg('input')!)) {
       throwToolExit('${stringArg('input')} does not exist.');
     }
     return super.validateCommand();
@@ -85,7 +83,7 @@ class SymbolizeCommand extends FlutterCommand {
     IOSink output;
 
     // Configure output to either specified file or stdout.
-    if (argResults.wasParsed('output')) {
+    if (argResults?.wasParsed('output') == true) {
       final File outputFile = _fileSystem.file(stringArg('output'));
       if (!outputFile.parent.existsSync()) {
         outputFile.parent.createSync(recursive: true);
@@ -101,7 +99,7 @@ class SymbolizeCommand extends FlutterCommand {
     }
 
     // Configure input from either specified file or stdin.
-    if (argResults.wasParsed('input')) {
+    if (argResults?.wasParsed('input') == true) {
       input = _fileSystem.file(stringArg('input')).openRead();
     } else {
       input = _stdio.stdin;
@@ -121,7 +119,7 @@ class SymbolizeCommand extends FlutterCommand {
 typedef SymbolsTransformer = StreamTransformer<String, String> Function(Uint8List);
 
 StreamTransformer<String, String> _defaultTransformer(Uint8List symbols) {
-  final Dwarf dwarf = Dwarf.fromBytes(symbols);
+  final Dwarf? dwarf = Dwarf.fromBytes(symbols);
   if (dwarf == null) {
     throwToolExit('Failed to decode symbols file');
   }
@@ -137,7 +135,7 @@ StreamTransformer<String, String> _testTransformer(Uint8List buffer) {
     handleDone: (EventSink<String> sink) {
       sink.close();
     },
-    handleError: (dynamic error, StackTrace stackTrace, EventSink<String> sink) {
+    handleError: (Object error, StackTrace stackTrace, EventSink<String> sink) {
       sink.addError(error, stackTrace);
     }
   );
@@ -167,12 +165,12 @@ class DwarfSymbolizationService {
   /// Throws a [ToolExit] if the symbols cannot be parsed or the stack trace
   /// cannot be decoded.
   Future<void> decode({
-    @required Stream<List<int>> input,
-    @required IOSink output,
-    @required Uint8List symbols,
+    required Stream<List<int>> input,
+    required IOSink output,
+    required Uint8List symbols,
   }) async {
     final Completer<void> onDone = Completer<void>();
-    StreamSubscription<void> subscription;
+    StreamSubscription<void>? subscription;
     subscription = input
       .cast<List<int>>()
       .transform(const Utf8Decoder())
@@ -182,7 +180,7 @@ class DwarfSymbolizationService {
         try {
           output.writeln(line);
         } on Exception catch(e, s) {
-          subscription.cancel().whenComplete(() {
+          subscription?.cancel().whenComplete(() {
             if (!onDone.isCompleted) {
               onDone.completeError(e, s);
             }
diff --git a/packages/flutter_tools/lib/src/template.dart b/packages/flutter_tools/lib/src/template.dart
index 851de59c170..da0fe4a54b0 100644
--- a/packages/flutter_tools/lib/src/template.dart
+++ b/packages/flutter_tools/lib/src/template.dart
@@ -38,7 +38,7 @@ const List<String> kReservedKotlinKeywords = <String>['when', 'in'];
 /// Files in the destination will contain none of the '.tmpl', '.copy.tmpl',
 /// 'img.tmpl', or '-<language>.tmpl' extensions.
 class Template {
-  factory Template(Directory templateSource, Directory imageSourceDir, {
+  factory Template(Directory templateSource, Directory? imageSourceDir, {
     required FileSystem fileSystem,
     required Logger logger,
     required TemplateRenderer templateRenderer,
@@ -46,7 +46,7 @@ class Template {
   }) {
     return Template._(
       <Directory>[templateSource],
-      <Directory>[imageSourceDir],
+      imageSourceDir != null ? <Directory>[imageSourceDir] : <Directory>[],
       fileSystem: fileSystem,
       logger: logger,
       templateRenderer: templateRenderer,