Migrate dev/bots to null safety (#86522)

dev/bots/browser.dart

@@ -6,7 +6,6 @@ import 'dart:async';
 import 'dart:io' as io;
 
 import 'package:flutter_devicelab/framework/browser.dart';
-import 'package:meta/meta.dart';
 import 'package:shelf/shelf.dart';
 import 'package:shelf/shelf_io.dart' as shelf_io;
 import 'package:shelf_static/shelf_static.dart';
@@ -21,13 +20,13 @@ import 'package:shelf_static/shelf_static.dart';
 /// request to "/test-result" containing result data as plain text body of the
 /// request. This function has no opinion about what that string contains.
 Future<String> evalTestAppInChrome({
-  @required String appUrl,
-  @required String appDirectory,
+  required String appUrl,
+  required String appDirectory,
   int serverPort = 8080,
   int browserDebugPort = 8081,
 }) async {
-  io.HttpServer server;
-  Chrome chrome;
+  io.HttpServer? server;
+  Chrome? chrome;
   try {
     final Completer<String> resultCompleter = Completer<String>();
     server = await io.HttpServer.bind('localhost', serverPort);
@@ -63,13 +62,13 @@ class AppServer {
   AppServer._(this._server, this.chrome, this.onChromeError);
 
   static Future<AppServer> start({
-    @required String appUrl,
-    @required String appDirectory,
-    @required String cacheControl,
+    required String appUrl,
+    required String appDirectory,
+    required String cacheControl,
     int serverPort = 8080,
     int browserDebugPort = 8081,
     bool headless = true,
-    List<Handler> additionalRequestHandlers,
+    List<Handler>? additionalRequestHandlers,
   }) async {
     io.HttpServer server;
     Chrome chrome;
@@ -106,7 +105,7 @@ class AppServer {
   final Chrome chrome;
 
   Future<void> stop() async {
-    chrome?.stop();
-    await _server?.close();
+    chrome.stop();
+    await _server.close();
   }
 }

dev/bots/flutter_compact_formatter.dart

@@ -5,8 +5,6 @@
 import 'dart:convert';
 import 'dart:io';
 
-import 'package:meta/meta.dart';
-
 final Stopwatch _stopwatch = Stopwatch();
 
 /// A wrapper around package:test's JSON reporter.
@@ -75,7 +73,7 @@ class FlutterCompactFormatter {
   ///
   /// Callers are responsible for splitting multiple lines before calling this
   /// method.
-  TestResult processRawOutput(String raw) {
+  TestResult? processRawOutput(String raw) {
     assert(raw != null);
     // We might be getting messages from Flutter Tool about updating/building.
     if (!raw.startsWith('{')) {
@@ -83,7 +81,7 @@ class FlutterCompactFormatter {
       return null;
     }
     final Map<String, dynamic> decoded = json.decode(raw) as Map<String, dynamic>;
-    final TestResult originalResult = _tests[decoded['testID']];
+    final TestResult? originalResult = _tests[decoded['testID']];
     switch (decoded['type'] as String) {
       case 'done':
         stdout.write(_clearLine);
@@ -104,9 +102,9 @@ class FlutterCompactFormatter {
         _tests[testData['id'] as int] = TestResult(
           id: testData['id'] as int,
           name: testData['name'] as String,
-          line: testData['root_line'] as int ?? testData['line'] as int,
-          column: testData['root_column'] as int ?? testData['column'] as int,
-          path: testData['root_url'] as String ?? testData['url'] as String,
+          line: testData['root_line'] as int? ?? testData['line'] as int,
+          column: testData['root_column'] as int? ?? testData['column'] as int,
+          path: testData['root_url'] as String? ?? testData['url'] as String,
           startTime: decoded['time'] as int,
         );
         break;
@@ -173,9 +171,9 @@ class FlutterCompactFormatter {
         case TestStatus.failed:
           failed.addAll(<String>[
             '$_bold${_red}Failed ${result.name} (${result.pathLineColumn}):',
-            result.errorMessage,
+            result.errorMessage!,
             _noColor + _red,
-            result.stackTrace,
+            result.stackTrace!,
           ]);
           failed.addAll(result.messages);
           failed.add(_noColor);
@@ -209,12 +207,12 @@ enum TestStatus {
 /// The detailed status of a test run.
 class TestResult {
   TestResult({
-    @required this.id,
-    @required this.name,
-    @required this.line,
-    @required this.column,
-    @required this.path,
-    @required this.startTime,
+    required this.id,
+    required this.name,
+    required this.line,
+    required this.column,
+    required this.path,
+    required this.startTime,
     this.status = TestStatus.started,
   })  : assert(id != null),
         assert(name != null),
@@ -254,13 +252,13 @@ class TestResult {
 
   /// The error message from the test, from an `expect`, an [Exception] or
   /// [Error].
-  String errorMessage;
+  String? errorMessage;
 
   /// The stacktrace from a test failure.
-  String stackTrace;
+  String? stackTrace;
 
   /// The time, in milliseconds relative to suite startup, that the test ended.
-  int endTime;
+  int? endTime;
 
   /// The total time, in milliseconds, that the test took.
   int get totalTime => (endTime ?? _stopwatch.elapsedMilliseconds) - startTime;

dev/bots/prepare_package.dart

@@ -11,7 +11,6 @@ import 'package:args/args.dart';
 import 'package:crypto/crypto.dart';
 import 'package:crypto/src/digest_sink.dart';
 import 'package:http/http.dart' as http;
-import 'package:meta/meta.dart' show required;
 import 'package:path/path.dart' as path;
 import 'package:platform/platform.dart' show Platform, LocalPlatform;
 import 'package:process/process.dart';
@@ -32,7 +31,7 @@ class PreparePackageException implements Exception {
   PreparePackageException(this.message, [this.result]);
 
   final String message;
-  final ProcessResult result;
+  final ProcessResult? result;
   int get exitCode => result?.exitCode ?? -1;
 
   @override
@@ -41,7 +40,7 @@ class PreparePackageException implements Exception {
     if (message != null) {
       output += ': $message';
     }
-    final String stderr = result?.stderr as String ?? '';
+    final String stderr = result?.stderr as String? ?? '';
     if (stderr.isNotEmpty) {
       output += ':\n$stderr';
     }
@@ -60,7 +59,6 @@ String getBranchName(Branch branch) {
     case Branch.stable:
       return 'stable';
   }
-  return null;
 }
 
 Branch fromBranchName(String name) {
@@ -81,7 +79,7 @@ Branch fromBranchName(String name) {
 /// properly without dropping any.
 class ProcessRunner {
   ProcessRunner({
-    ProcessManager processManager,
+    ProcessManager? processManager,
     this.subprocessOutput = true,
     this.defaultWorkingDirectory,
     this.platform = const LocalPlatform(),
@@ -102,10 +100,10 @@ class ProcessRunner {
 
   /// Sets the default directory used when `workingDirectory` is not specified
   /// to [runProcess].
-  final Directory defaultWorkingDirectory;
+  final Directory? defaultWorkingDirectory;
 
   /// The environment to run processes with.
-  Map<String, String> environment;
+  late Map<String, String> environment;
 
   /// Run the command and arguments in `commandLine` as a sub-process from
   /// `workingDirectory` if set, or the [defaultWorkingDirectory] if not. Uses
@@ -115,7 +113,7 @@ class ProcessRunner {
   /// command completes with a non-zero exit code.
   Future<String> runProcess(
     List<String> commandLine, {
-    Directory workingDirectory,
+    Directory? workingDirectory,
     bool failOk = false,
   }) async {
     workingDirectory ??= defaultWorkingDirectory ?? Directory.current;
@@ -125,7 +123,7 @@ class ProcessRunner {
     final List<int> output = <int>[];
     final Completer<void> stdoutComplete = Completer<void>();
     final Completer<void> stderrComplete = Completer<void>();
-    Process process;
+    late Process process;
     Future<int> allComplete() async {
       await stderrComplete.future;
       await stdoutComplete.future;
@@ -197,10 +195,10 @@ class ArchiveCreator {
     this.revision,
     this.branch, {
     this.strict = true,
-    ProcessManager processManager,
+    ProcessManager? processManager,
     bool subprocessOutput = true,
     this.platform = const LocalPlatform(),
-    HttpReader httpReader,
+    HttpReader? httpReader,
   })  : assert(revision.length == 40),
         flutterRoot = Directory(path.join(tempDir.path, 'flutter')),
         httpReader = httpReader ?? http.readBytes,
@@ -252,9 +250,9 @@ class ArchiveCreator {
   /// [http.readBytes].
   final HttpReader httpReader;
 
-  File _outputFile;
-  String _version;
-  String _flutter;
+  late File _outputFile;
+  late String _version;
+  late String _flutter;
 
   /// Get the name of the channel as a string.
   String get branchName => getBranchName(branch);
@@ -446,14 +444,14 @@ class ArchiveCreator {
     }
   }
 
-  Future<String> _runFlutter(List<String> args, {Directory workingDirectory}) {
+  Future<String> _runFlutter(List<String> args, {Directory? workingDirectory}) {
     return _processRunner.runProcess(
       <String>[_flutter, ...args],
       workingDirectory: workingDirectory ?? flutterRoot,
     );
   }
 
-  Future<String> _runGit(List<String> args, {Directory workingDirectory}) {
+  Future<String> _runGit(List<String> args, {Directory? workingDirectory}) {
     return _processRunner.runProcess(
       <String>['git', ...args],
       workingDirectory: workingDirectory ?? flutterRoot,
@@ -462,7 +460,7 @@ class ArchiveCreator {
 
   /// Unpacks the given zip file into the currentDirectory (if set), or the
   /// same directory as the archive.
-  Future<String> _unzipArchive(File archive, {Directory workingDirectory}) {
+  Future<String> _unzipArchive(File archive, {Directory? workingDirectory}) {
     workingDirectory ??= Directory(path.dirname(archive.absolute.path));
     List<String> commandLine;
     if (platform.isWindows) {
@@ -532,7 +530,7 @@ class ArchivePublisher {
     this.version,
     this.outputFile,
     this.dryRun, {
-    ProcessManager processManager,
+    ProcessManager? processManager,
     bool subprocessOutput = true,
     this.platform = const LocalPlatform(),
   })  : assert(revision.length == 40),
@@ -662,7 +660,7 @@ class ArchivePublisher {
 
   Future<String> _runGsUtil(
     List<String> args, {
-    Directory workingDirectory,
+    Directory? workingDirectory,
     bool failOk = false,
   }) async {
     if (dryRun) {
@@ -671,7 +669,7 @@ class ArchivePublisher {
     }
     if (platform.isWindows) {
       return _processRunner.runProcess(
-        <String>['python', path.join(platform.environment['DEPOT_TOOLS'], 'gsutil.py'), '--', ...args],
+        <String>['python', path.join(platform.environment['DEPOT_TOOLS']!, 'gsutil.py'), '--', ...args],
         workingDirectory: workingDirectory,
         failOk: failOk,
       );
@@ -699,14 +697,14 @@ class ArchivePublisher {
   }
 
   Future<String> _cloudCopy({
-    @required String src,
-    @required String dest,
-    int cacheSeconds,
+    required String src,
+    required String dest,
+    int? cacheSeconds,
   }) async {
     // We often don't have permission to overwrite, but
     // we have permission to remove, so that's what we do.
     await _runGsUtil(<String>['rm', dest], failOk: true);
-    String mimeType;
+    String? mimeType;
     if (dest.endsWith('.tar.xz')) {
       mimeType = 'application/x-gtar';
     }
@@ -841,7 +839,7 @@ Future<void> main(List<String> rawArguments) async {
   final Branch branch = fromBranchName(parsedArguments['branch'] as String);
   final ArchiveCreator creator = ArchiveCreator(tempDir, outputDir, revision, branch, strict: parsedArguments['publish'] as bool);
   int exitCode = 0;
-  String message;
+  late String message;
   try {
     final String version = await creator.initializeRepo();
     final File outputFile = await creator.createArchive();

dev/bots/pubspec.yaml

@@ -2,7 +2,7 @@ name: tests_on_bots
 description: Scripts which run on bots.
 
 environment:
-  sdk: ">=2.2.2 <3.0.0"
+  sdk: ">=2.12.0 <3.0.0"
 
 dependencies:
   args: 2.1.1

dev/bots/run_command.dart

@@ -19,12 +19,12 @@ import 'utils.dart';
 /// code fails the test immediately by exiting the test process with exit code
 /// 1.
 Stream<String> runAndGetStdout(String executable, List<String> arguments, {
-  String workingDirectory,
-  Map<String, String> environment,
+  String? workingDirectory,
+  Map<String, String>? environment,
   bool expectNonZeroExit = false,
 }) async* {
   final StreamController<String> output = StreamController<String>();
-  final Future<CommandResult> command = runCommand(
+  final Future<CommandResult?> command = runCommand(
     executable,
     arguments,
     workingDirectory: workingDirectory,
@@ -52,8 +52,8 @@ class Command {
   final io.Process process;
 
   final Stopwatch _time;
-  final Future<List<List<int>>> _savedStdout;
-  final Future<List<List<int>>> _savedStderr;
+  final Future<List<List<int>>>? _savedStdout;
+  final Future<List<List<int>>>? _savedStderr;
 
   /// Evaluates when the [process] exits.
   ///
@@ -63,8 +63,8 @@ class Command {
     _time.stop();
 
     // Saved output is null when OutputMode.print is used.
-    final String flattenedStdout = _savedStdout != null ? _flattenToString(await _savedStdout) : null;
-    final String flattenedStderr = _savedStderr != null ? _flattenToString(await _savedStderr) : null;
+    final String? flattenedStdout = _savedStdout != null ? _flattenToString((await _savedStdout)!) : null;
+    final String? flattenedStderr = _savedStderr != null ? _flattenToString((await _savedStderr)!) : null;
     return CommandResult._(exitCode, _time.elapsed, flattenedStdout, flattenedStderr);
   }
 }
@@ -80,10 +80,10 @@ class CommandResult {
   final Duration elapsedTime;
 
   /// Standard output decoded as a string using UTF8 decoder.
-  final String flattenedStdout;
+  final String? flattenedStdout;
 
   /// Standard error output decoded as a string using UTF8 decoder.
-  final String flattenedStderr;
+  final String? flattenedStderr;
 }
 
 /// Starts the `executable` and returns a command object representing the
@@ -97,11 +97,11 @@ class CommandResult {
 /// `outputMode` controls where the standard output from the command process
 /// goes. See [OutputMode].
 Future<Command> startCommand(String executable, List<String> arguments, {
-  String workingDirectory,
-  Map<String, String> environment,
+  String? workingDirectory,
+  Map<String, String>? environment,
   OutputMode outputMode = OutputMode.print,
-  bool Function(String) removeLine,
-  void Function(String, io.Process) outputListener,
+  bool Function(String)? removeLine,
+  void Function(String, io.Process)? outputListener,
 }) async {
   final String commandDescription = '${path.relative(executable, from: workingDirectory)} ${arguments.join(' ')}';
   final String relativeWorkingDir = path.relative(workingDirectory ?? io.Directory.current.path);
@@ -113,7 +113,7 @@ Future<Command> startCommand(String executable, List<String> arguments, {
     environment: environment,
   );
 
-  Future<List<List<int>>> savedStdout, savedStderr;
+  Future<List<List<int>>>? savedStdout, savedStderr;
   final Stream<List<int>> stdoutSource = process.stdout
     .transform<String>(const Utf8Decoder())
     .transform(const LineSplitter())
@@ -150,27 +150,22 @@ Future<Command> startCommand(String executable, List<String> arguments, {
 /// an indefinitely running process, for example, by waiting until the process
 /// emits certain output.
 ///
-/// Returns the result of the finished process, or null if `skip` is true.
+/// Returns the result of the finished process.
 ///
 /// `outputMode` controls where the standard output from the command process
 /// goes. See [OutputMode].
 Future<CommandResult> runCommand(String executable, List<String> arguments, {
-  String workingDirectory,
-  Map<String, String> environment,
+  String? workingDirectory,
+  Map<String, String>? environment,
   bool expectNonZeroExit = false,
-  int expectedExitCode,
-  String failureMessage,
+  int? expectedExitCode,
+  String? failureMessage,
   OutputMode outputMode = OutputMode.print,
-  bool skip = false,
-  bool Function(String) removeLine,
-  void Function(String, io.Process) outputListener,
+  bool Function(String)? removeLine,
+  void Function(String, io.Process)? outputListener,
 }) async {
   final String commandDescription = '${path.relative(executable, from: workingDirectory)} ${arguments.join(' ')}';
   final String relativeWorkingDir = path.relative(workingDirectory ?? io.Directory.current.path);
-  if (skip) {
-    printProgress('SKIPPING', relativeWorkingDir, commandDescription);
-    return null;
-  }
 
   final Command command = await startCommand(executable, arguments,
     workingDirectory: workingDirectory,

dev/bots/service_worker_test.dart

@@ -5,7 +5,6 @@
 import 'dart:async';
 import 'dart:io';
 
-import 'package:meta/meta.dart';
 import 'package:path/path.dart' as path;
 import 'package:shelf/shelf.dart';
 
@@ -37,7 +36,7 @@ Future<void> _setAppVersion(int version) async {
   );
 }
 
-Future<void> _rebuildApp({ @required int version }) async {
+Future<void> _rebuildApp({ required int version }) async {
   await _setAppVersion(version);
   await runCommand(
     _flutter,
@@ -56,7 +55,7 @@ Future<void> _rebuildApp({ @required int version }) async {
 
 /// A drop-in replacement for `package:test` expect that can run outside the
 /// test zone.
-void expect(Object actual, Object expected) {
+void expect(Object? actual, Object? expected) {
   final Matcher matcher = wrapMatcher(expected);
   final Map<Object, Object> matchState = <Object, Object>{};
   if (matcher.matches(actual, matchState)) {
@@ -68,7 +67,7 @@ void expect(Object actual, Object expected) {
 }
 
 Future<void> runWebServiceWorkerTest({
-  @required bool headless,
+  required bool headless,
 }) async {
   await _rebuildApp(version: 1);
 
@@ -78,25 +77,25 @@ Future<void> runWebServiceWorkerTest({
     requestedPathCounts.clear();
   }
 
-  AppServer server;
+  AppServer? server;
   Future<void> waitForAppToLoad(Map<String, int> waitForCounts) async {
     print('Waiting for app to load $waitForCounts');
-    await Future.any(<Future<void>>[
+    await Future.any(<Future<Object?>>[
       () async {
         while (!waitForCounts.entries.every((MapEntry<String, int> entry) => (requestedPathCounts[entry.key] ?? 0) >= entry.value)) {
           await Future<void>.delayed(const Duration(milliseconds: 100));
         }
       }(),
-      server.onChromeError.then((String error) {
+      server!.onChromeError.then((String error) {
         throw Exception('Chrome error: $error');
       }),
     ]);
   }
 
-  String reportedVersion;
+  String? reportedVersion;
 
   Future<void> startAppServer({
-    @required String cacheControl,
+    required String cacheControl,
   }) async {
     final int serverPort = await findAvailablePort();
     final int browserDebugPort = await findAvailablePort();
@@ -113,7 +112,7 @@ Future<void> runWebServiceWorkerTest({
         (Request request) {
           final String requestedPath = request.url.path;
           requestedPathCounts.putIfAbsent(requestedPath, () => 0);
-          requestedPathCounts[requestedPath] += 1;
+          requestedPathCounts[requestedPath] = requestedPathCounts[requestedPath]! + 1;
           if (requestedPath == 'CLOSE') {
             reportedVersion = request.url.queryParameters['version'];
             return Response.ok('OK');
@@ -158,7 +157,7 @@ Future<void> runWebServiceWorkerTest({
     reportedVersion = null;
 
     print('With cache: test page reload');
-    await server.chrome.reloadPage();
+    await server!.chrome.reloadPage();
     await waitForAppToLoad(<String, int>{
       'CLOSE': 1,
       'flutter_service_worker.js': 1,
@@ -175,7 +174,7 @@ Future<void> runWebServiceWorkerTest({
     await _rebuildApp(version: 2);
 
     // Since we're caching, we need to ignore cache when reloading the page.
-    await server.chrome.reloadPage(ignoreCache: true);
+    await server!.chrome.reloadPage(ignoreCache: true);
     await waitForAppToLoad(<String, int>{
       'CLOSE': 1,
       'flutter_service_worker.js': 2,
@@ -195,7 +194,7 @@ Future<void> runWebServiceWorkerTest({
 
     expect(reportedVersion, '2');
     reportedVersion = null;
-    await server.stop();
+    await server!.stop();
 
 
     //////////////////////////////////////////////////////
@@ -231,7 +230,7 @@ Future<void> runWebServiceWorkerTest({
     reportedVersion = null;
 
     print('No cache: test page reload');
-    await server.chrome.reloadPage();
+    await server!.chrome.reloadPage();
     await waitForAppToLoad(<String, int>{
       'CLOSE': 1,
       'flutter_service_worker.js': 1,
@@ -254,7 +253,7 @@ Future<void> runWebServiceWorkerTest({
     // refresh when running Chrome manually as normal. At the time of writing
     // this test I wasn't able to figure out what's wrong with the way we run
     // Chrome from tests.
-    await server.chrome.reloadPage(ignoreCache: true);
+    await server!.chrome.reloadPage(ignoreCache: true);
     await waitForAppToLoad(<String, int>{
       'CLOSE': 1,
       'flutter_service_worker.js': 1,

dev/bots/test/prepare_package_test.dart

@@ -74,16 +74,16 @@ void main() {
       });
     });
     group('ArchiveCreator for $platformName', () {
-      ArchiveCreator creator;
-      Directory tempDir;
+      late ArchiveCreator creator;
+      late Directory tempDir;
       Directory flutterDir;
       Directory cacheDir;
-      FakeProcessManager processManager;
+      late FakeProcessManager processManager;
       final List<List<String>> args = <List<String>>[];
       final List<Map<Symbol, dynamic>> namedArgs = <Map<Symbol, dynamic>>[];
-      String flutter;
+      late String flutter;
 
-      Future<Uint8List> fakeHttpReader(Uri url, {Map<String, String> headers}) {
+      Future<Uint8List> fakeHttpReader(Uri url, {Map<String, String>? headers}) {
         return Future<Uint8List>.value(Uint8List(0));
       }
 
@@ -118,7 +118,7 @@ void main() {
         final String archiveName = path.join(tempDir.absolute.path,
             'flutter_${platformName}_v1.2.3-dev${platform.isLinux ? '.tar.xz' : '.zip'}');
 
-        processManager.addCommands(convertResults(<String, List<ProcessResult>>{
+        processManager.addCommands(convertResults(<String, List<ProcessResult>?>{
           'git clone -b dev https://chromium.googlesource.com/external/github.com/flutter/flutter': null,
           'git reset --hard $testRef': null,
           'git remote set-url origin https://github.com/flutter/flutter.git': null,
@@ -147,7 +147,7 @@ void main() {
         final String createBase = path.join(tempDir.absolute.path, 'create_');
         final String archiveName = path.join(tempDir.absolute.path,
             'flutter_${platformName}_v1.2.3-dev${platform.isLinux ? '.tar.xz' : '.zip'}');
-        final Map<String, List<ProcessResult>> calls = <String, List<ProcessResult>>{
+        final Map<String, List<ProcessResult>?> calls = <String, List<ProcessResult>?>{
           'git clone -b dev https://chromium.googlesource.com/external/github.com/flutter/flutter': null,
           'git reset --hard $testRef': null,
           'git remote set-url origin https://github.com/flutter/flutter.git': null,
@@ -197,7 +197,7 @@ void main() {
         final String createBase = path.join(tempDir.absolute.path, 'create_');
         final String archiveName = path.join(tempDir.absolute.path,
             'flutter_${platformName}_v1.2.3-dev${platform.isLinux ? '.tar.xz' : '.zip'}');
-        final Map<String, List<ProcessResult>> calls = <String, List<ProcessResult>>{
+        final Map<String, List<ProcessResult>?> calls = <String, List<ProcessResult>?>{
           'git clone -b dev https://chromium.googlesource.com/external/github.com/flutter/flutter': null,
           'git reset --hard $testRef': null,
           'git remote set-url origin https://github.com/flutter/flutter.git': null,
@@ -239,7 +239,7 @@ void main() {
             'flutter_${platformName}_v1.2.3-dev${platform.isLinux ? '.tar.xz' : '.zip'}');
         final ProcessResult codesignFailure = ProcessResult(1, 1, '', 'code object is not signed at all');
         final String binPath = path.join(tempDir.path, 'flutter', 'bin', 'cache', 'dart-sdk', 'bin', 'dart');
-        final Map<String, List<ProcessResult>> calls = <String, List<ProcessResult>>{
+        final Map<String, List<ProcessResult>?> calls = <String, List<ProcessResult>?>{
           'git clone -b dev https://chromium.googlesource.com/external/github.com/flutter/flutter': null,
           'git reset --hard $testRef': null,
           'git remote set-url origin https://github.com/flutter/flutter.git': null,
@@ -286,8 +286,8 @@ void main() {
     });
 
     group('ArchivePublisher for $platformName', () {
-      FakeProcessManager processManager;
-      Directory tempDir;
+      late FakeProcessManager processManager;
+      late Directory tempDir;
       final String gsutilCall = platform.isWindows
           ? 'python ${path.join("D:", "depot_tools", "gsutil.py")}'
           : 'gsutil.py';
@@ -346,7 +346,7 @@ void main() {
 ''';
         File(jsonPath).writeAsStringSync(releasesJson);
         File(archivePath).writeAsStringSync('archive contents');
-        final Map<String, List<ProcessResult>> calls = <String, List<ProcessResult>>{
+        final Map<String, List<ProcessResult>?> calls = <String, List<ProcessResult>?>{
           // This process fails because the file does NOT already exist
           '$gsutilCall -- stat $gsArchivePath': <ProcessResult>[ProcessResult(0, 1, '', '')],
           '$gsutilCall -- rm $gsArchivePath': null,
@@ -442,7 +442,7 @@ void main() {
 ''';
         File(jsonPath).writeAsStringSync(releasesJson);
         File(archivePath).writeAsStringSync('archive contents');
-        final Map<String, List<ProcessResult>> calls = <String, List<ProcessResult>>{
+        final Map<String, List<ProcessResult>?> calls = <String, List<ProcessResult>?>{
           // This process fails because the file does NOT already exist
           '$gsutilCall -- stat $gsArchivePath': <ProcessResult>[ProcessResult(0, 1, '', '')],
           '$gsutilCall -- rm $gsArchivePath': null,
@@ -552,7 +552,7 @@ void main() {
 ''';
         File(jsonPath).writeAsStringSync(releasesJson);
         File(archivePath).writeAsStringSync('archive contents');
-        final Map<String, List<ProcessResult>> calls = <String, List<ProcessResult>>{
+        final Map<String, List<ProcessResult>?> calls = <String, List<ProcessResult>?>{
           '$gsutilCall -- rm $gsArchivePath': null,
           '$gsutilCall -- -h Content-Type:$archiveMime cp $archivePath $gsArchivePath': null,
           '$gsutilCall -- cp $gsJsonPath $jsonPath': null,
@@ -567,10 +567,10 @@ void main() {
   }
 }
 
-List<FakeCommand> convertResults(Map<String, List<ProcessResult>> results) {
+List<FakeCommand> convertResults(Map<String, List<ProcessResult>?> results) {
   final List<FakeCommand> commands = <FakeCommand>[];
   for (final String key in results.keys) {
-    final List<ProcessResult> candidates = results[key];
+    final List<ProcessResult>? candidates = results[key];
     final List<String> args = key.split(' ');
     if (candidates == null) {
       commands.add(FakeCommand(
@@ -581,8 +581,8 @@ List<FakeCommand> convertResults(Map<String, List<ProcessResult>> results) {
         commands.add(FakeCommand(
           command: args,
           exitCode: result.exitCode,
-          stderr: result.stderr?.toString(),
-          stdout: result.stdout?.toString(),
+          stderr: result.stderr.toString(),
+          stdout: result.stdout.toString(),
         ));
       }
     }

dev/bots/test/sdk_directory_has_space_test.dart

@@ -12,10 +12,10 @@ void main() {
   test('We are in a directory with a space in it', () async {
     // The Flutter SDK should be in a directory with a space in it, to make sure
     // our tools support that.
-    final String expectedName = Platform.environment['FLUTTER_SDK_PATH_WITH_SPACE'];
+    final String? expectedName = Platform.environment['FLUTTER_SDK_PATH_WITH_SPACE'];
     expect(expectedName, 'flutter sdk');
     expect(expectedName, contains(' '));
     final List<String> parts = path.split(Directory.current.absolute.path);
-    expect(parts.reversed.take(3), <String>['bots', 'dev', expectedName]);
+    expect(parts.reversed.take(3), <String?>['bots', 'dev', expectedName]);
   }, skip: true); // https://github.com/flutter/flutter/issues/62919
 }

dev/bots/test/test_test.dart

@@ -23,7 +23,7 @@ void expectExitCode(ProcessResult result, int expectedExitCode) {
 
 void main() {
   group('verifyVersion()', () {
-    MemoryFileSystem fileSystem;
+    late MemoryFileSystem fileSystem;
 
     setUp(() {
       fileSystem = MemoryFileSystem.test();
@@ -97,7 +97,7 @@ void main() {
     const ProcessManager processManager = LocalProcessManager();
 
     Future<ProcessResult> runScript(
-        [Map<String, String> environment, List<String> otherArgs = const <String>[]]) async {
+        [Map<String, String>? environment, List<String> otherArgs = const <String>[]]) async {
       final String dart = path.absolute(
           path.join('..', '..', 'bin', 'cache', 'dart-sdk', 'bin', 'dart'));
       final ProcessResult scriptProcess = processManager.runSync(<String>[

dev/bots/unpublish_package.dart

@@ -32,7 +32,7 @@ class UnpublishException implements Exception {
   UnpublishException(this.message, [this.result]);
 
   final String message;
-  final ProcessResult result;
+  final ProcessResult? result;
   int get exitCode => result?.exitCode ?? -1;
 
   @override
@@ -41,7 +41,7 @@ class UnpublishException implements Exception {
     if (message != null) {
       output += ': $message';
     }
-    final String stderr = result?.stderr as String ?? '';
+    final String stderr = result?.stderr as String? ?? '';
     if (stderr.isNotEmpty) {
       output += ':\n$stderr';
     }
@@ -60,10 +60,9 @@ String getChannelName(Channel channel) {
     case Channel.stable:
       return 'stable';
   }
-  return null;
 }
 
-Channel fromChannelName(String name) {
+Channel fromChannelName(String? name) {
   switch (name) {
     case 'beta':
       return Channel.beta;
@@ -87,7 +86,6 @@ String getPublishedPlatform(PublishedPlatform platform) {
     case PublishedPlatform.windows:
       return 'windows';
   }
-  return null;
 }
 
 PublishedPlatform fromPublishedPlatform(String name) {
@@ -135,10 +133,10 @@ class ProcessRunner {
 
   /// Sets the default directory used when `workingDirectory` is not specified
   /// to [runProcess].
-  final Directory defaultWorkingDirectory;
+  final Directory? defaultWorkingDirectory;
 
   /// The environment to run processes with.
-  Map<String, String> environment;
+  late Map<String, String> environment;
 
   /// Run the command and arguments in `commandLine` as a sub-process from
   /// `workingDirectory` if set, or the [defaultWorkingDirectory] if not. Uses
@@ -148,7 +146,7 @@ class ProcessRunner {
   /// command completes with a non-zero exit code.
   Future<String> runProcess(
     List<String> commandLine, {
-    Directory workingDirectory,
+    Directory? workingDirectory,
     bool failOk = false,
   }) async {
     workingDirectory ??= defaultWorkingDirectory ?? Directory.current;
@@ -158,7 +156,7 @@ class ProcessRunner {
     final List<int> output = <int>[];
     final Completer<void> stdoutComplete = Completer<void>();
     final Completer<void> stderrComplete = Completer<void>();
-    Process process;
+    late Process process;
     Future<int> allComplete() async {
       await stderrComplete.future;
       await stdoutComplete.future;
@@ -221,12 +219,12 @@ class ArchiveUnpublisher {
     this.channels,
     this.platform, {
     this.confirmed = false,
-    ProcessManager processManager,
+    ProcessManager? processManager,
     bool subprocessOutput = true,
   })  : assert(revisionsBeingRemoved.length == 40),
         metadataGsPath = '$gsReleaseFolder/${getMetadataFilename(platform)}',
         _processRunner = ProcessRunner(
-          processManager: processManager,
+          processManager: processManager ?? const LocalProcessManager(),
           subprocessOutput: subprocessOutput,
         );
 
@@ -249,8 +247,8 @@ class ArchiveUnpublisher {
     final Map<Channel, Map<String, String>> paths = await _getArchivePaths(releases);
     releases.removeWhere((Map<String, String> value) => revisionsBeingRemoved.contains(value['hash']) && channels.contains(fromChannelName(value['channel'])));
     releases.sort((Map<String, String> a, Map<String, String> b) {
-      final DateTime aDate = DateTime.parse(a['release_date']);
-      final DateTime bDate = DateTime.parse(b['release_date']);
+      final DateTime aDate = DateTime.parse(a['release_date']!);
+      final DateTime bDate = DateTime.parse(b['release_date']!);
       return bDate.compareTo(aDate);
     });
     jsonData['releases'] = releases;
@@ -277,12 +275,12 @@ class ArchiveUnpublisher {
     final Set<String> hashes = <String>{};
     final Map<Channel, Map<String, String>> paths = <Channel, Map<String, String>>{};
     for (final Map<String, String> revision in releases) {
-      final String hash = revision['hash'];
+      final String hash = revision['hash']!;
       final Channel channel = fromChannelName(revision['channel']);
       hashes.add(hash);
       if (revisionsBeingRemoved.contains(hash) && channels.contains(channel)) {
         paths[channel] ??= <String, String>{};
-        paths[channel][hash] = revision['archive'];
+        paths[channel]![hash] = revision['archive']!;
       }
     }
     final Set<String> missingRevisions = revisionsBeingRemoved.difference(hashes.intersection(revisionsBeingRemoved));
@@ -330,7 +328,7 @@ class ArchiveUnpublisher {
 
   Future<String> _runGsUtil(
     List<String> args, {
-    Directory workingDirectory,
+    Directory? workingDirectory,
     bool failOk = false,
     bool confirm = false,
   }) async {
@@ -351,7 +349,7 @@ class ArchiveUnpublisher {
     final List<String> files = <String>[];
     print('${confirmed ? 'Removing' : 'Would remove'} the following release archives:');
     for (final Channel channel in paths.keys) {
-      final Map<String, String> hashes = paths[channel];
+      final Map<String, String> hashes = paths[channel]!;
       for (final String hash in hashes.keys) {
         final String file = '$gsReleaseFolder/${hashes[hash]}';
         files.add(file);
@@ -367,7 +365,7 @@ class ArchiveUnpublisher {
     // We often don't have permission to overwrite, but
     // we have permission to remove, so that's what we do first.
     await _runGsUtil(<String>['rm', dest], failOk: true, confirm: confirmed);
-    String mimeType;
+    String? mimeType;
     if (dest.endsWith('.tar.xz')) {
       mimeType = 'application/x-gtar';
     }
@@ -497,8 +495,8 @@ Future<void> main(List<String> rawArguments) async {
   final List<String> platformOptions = platformArg.isNotEmpty ? platformArg : allowedPlatformNames;
   final List<PublishedPlatform> platforms = platformOptions.map<PublishedPlatform>((String value) => fromPublishedPlatform(value)).toList();
   int exitCode = 0;
-  String message;
-  String stack;
+  late String message;
+  late String stack;
   try {
     for (final PublishedPlatform platform in platforms) {
       final ArchiveUnpublisher publisher = ArchiveUnpublisher(