Migrate flutter_tool tool helper files to null safety (#78845)

packages/flutter_tools/lib/src/android/adb.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
-
 final RegExp _whitespace = RegExp(r'\s+');
 
 /// Convert adb device names into more human readable descriptions.

packages/flutter_tools/lib/src/android/android.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
-
 const int minApiLevel = 16;
 const String minVersionName = 'Jelly Bean';
 const String minVersionText = '4.1.x';

packages/flutter_tools/lib/src/base/template.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
-
 /// An indirection around our mustache templating system to avoid a
 /// dependency on mustache..
 abstract class TemplateRenderer {

packages/flutter_tools/lib/src/base/user_messages.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 'context.dart';
 import 'platform.dart';
 
@@ -16,7 +14,7 @@ class UserMessages {
       'Please report a bug at https://github.com/flutter/flutter/issues.';
 
   // Messages used in FlutterValidator
-  String flutterStatusInfo(String channel, String version, String os, String locale) =>
+  String flutterStatusInfo(String? channel, String? version, String os, String locale) =>
       'Channel ${channel ?? 'unknown'}, ${version ?? 'Unknown'}, on $os, locale $locale';
   String flutterVersion(String version, String flutterRoot) =>
       'Flutter version $version at $flutterRoot';

packages/flutter_tools/lib/src/build_system/hash.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:typed_data';
 
 /// Data from a non-linear mathematical function that functions as
@@ -51,7 +49,7 @@ class Md5Hash {
   int _remainingLength = 0;
   int _contentLength = 0;
 
-  void addChunk(Uint8List data, [int stop]) {
+  void addChunk(Uint8List data, [int? stop]) {
     assert(_remainingLength == 0);
     stop ??= data.length;
     int i = 0;

packages/flutter_tools/lib/src/isolated/mustache_template.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:mustache_template/mustache_template.dart';
 
 import '../base/template.dart';

packages/flutter_tools/lib/src/localizations/gen_l10n_templates.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
-
 const String emptyPubspecTemplate = '''
 # Generated by the flutter tool
 name: synthetic_package

packages/flutter_tools/lib/src/localizations/language_subtag_registry.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
-
 /// Cache of https://www.iana.org/assignments/language-subtag-registry/language-subtag-registry.
 const String languageSubtagRegistry = '''
 File-Date: 2020-03-16

packages/flutter_tools/lib/src/test/test_device.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 'package:meta/meta.dart';

packages/flutter_tools/lib/src/test/watcher.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 'test_device.dart';
 
 /// Callbacks for reporting progress while running tests.

packages/flutter_tools/lib/src/web/bootstrap.dart

@@ -2,9 +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:meta/meta.dart';
 import 'package:package_config/package_config.dart';
 
 /// The JavaScript bootstrap script to support in-browser hot restart.
@@ -17,8 +14,8 @@ import 'package:package_config/package_config.dart';
 /// and is responsible for bootstrapping the RequireJS modules and attaching
 /// the hot reload hooks.
 String generateBootstrapScript({
-  @required String requireUrl,
-  @required String mapperUrl,
+  required String requireUrl,
+  required String mapperUrl,
 }) {
   return '''
 "use strict";
@@ -54,9 +51,9 @@ document.head.appendChild(requireEl);
 /// `foo__bar__baz`. Rather than attempt to guess, we assume the first property of
 /// this object is the module.
 String generateMainModule({
-  @required String entrypoint,
-  @required bool nullAssertions,
-  @required bool nativeNullAssertions,
+  required String entrypoint,
+  required bool nullAssertions,
+  required bool nativeNullAssertions,
   String bootstrapModule = 'main_module.bootstrap',
 }) {
   // TODO(jonahwilliams): fix typo in dwds and update.
@@ -102,10 +99,10 @@ define("$bootstrapModule", ["$entrypoint", "dart_sdk"], function(app, dart_sdk)
 ///
 /// This hard-codes the device pixel ratio to 3.0 and a 2400 x 1800 window size.
 String generateTestEntrypoint({
-  @required String relativeTestPath,
-  @required String absolutePath,
-  @required String testConfigPath,
-  @required LanguageVersion languageVersion,
+  required String relativeTestPath,
+  required String absolutePath,
+  required String testConfigPath,
+  required LanguageVersion languageVersion,
 }) {
   return '''
   // @dart = ${languageVersion.major}.${languageVersion.minor}

packages/flutter_tools/tool/daemon_client.dart

@@ -2,14 +2,12 @@
 // 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:convert';
 import 'dart:io';
 
 import 'package:flutter_tools/src/base/common.dart';
 
-Process daemon;
+late Process daemon;
 
 // To use, start from the console and enter:
 //   version: print version
@@ -85,7 +83,7 @@ Future<void> main() async {
   });
 
   // Print in the callback can't fail.
-  unawaited(daemon.exitCode.then<void>((int code) {
+  unawaited(daemon.exitCode.then<int>((int code) {
     print('daemon exiting ($code)');
     exit(code);
   }));

packages/flutter_tools/tool/global_count.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:io';
 import 'package:path/path.dart' as path;
 
@@ -27,7 +25,7 @@ int countGlobalImports(Directory directory) {
     if (!file.path.endsWith('.dart') || file is! File) {
       continue;
     }
-    final bool hasImport = (file as File).readAsLinesSync().any((String line) {
+    final bool hasImport = file.readAsLinesSync().any((String line) {
       return globalImport.hasMatch(line);
     });
     if (hasImport) {

packages/flutter_tools/tool/unit_coverage.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:io';
 
 /// Produces a per-library coverage summary when fed an lcov file, sorted by
@@ -17,7 +15,7 @@ void main(List<String> args) {
   }
   final List<String> lines = File(args.single).readAsLinesSync();
   final List<Coverage> coverages = <Coverage>[];
-  Coverage currentCoverage;
+  Coverage? currentCoverage;
 
   for (final String line in lines) {
     if (line.startsWith('SF:')) {
@@ -26,9 +24,9 @@ void main(List<String> args) {
       coverages.add(currentCoverage);
     }
     if (line.startsWith('DA')) {
-      currentCoverage.totalLines += 1;
+      currentCoverage?.totalLines += 1;
       if (!line.endsWith(',0')) {
-        currentCoverage.testedLines += 1;
+        currentCoverage?.testedLines += 1;
       }
     }
     if (line == 'end_of_record') {
@@ -53,7 +51,7 @@ void main(List<String> args) {
 }
 
 class Coverage {
-  String library;
+  String? library;
   int totalLines = 0;
   int testedLines = 0;
 }