[flutter_tools] io cleanups to simplify null safety migration (#77955)

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

@@ -48,11 +48,10 @@ import 'dart:io' as io
     stdout;
 
 import 'package:meta/meta.dart';
+import 'package:file/file.dart';
 
-import '../globals.dart' as globals;
 import 'async_guard.dart';
-import 'context.dart';
-import 'file_system.dart';
+import 'platform.dart';
 import 'process.dart';
 
 export 'dart:io'
@@ -165,16 +164,18 @@ void restoreExitFunction() {
 /// [ProcessSignal] instances are available on this class (e.g. "send").
 class ProcessSignal {
   @visibleForTesting
-  const ProcessSignal(this._delegate);
+  const ProcessSignal(this._delegate, {@visibleForTesting Platform platform = const LocalPlatform()})
+    : _platform = platform;
 
-  static const ProcessSignal SIGWINCH = _PosixProcessSignal._(io.ProcessSignal.sigwinch);
-  static const ProcessSignal SIGTERM = _PosixProcessSignal._(io.ProcessSignal.sigterm);
-  static const ProcessSignal SIGUSR1 = _PosixProcessSignal._(io.ProcessSignal.sigusr1);
-  static const ProcessSignal SIGUSR2 = _PosixProcessSignal._(io.ProcessSignal.sigusr2);
-  static const ProcessSignal SIGINT =  ProcessSignal(io.ProcessSignal.sigint);
-  static const ProcessSignal SIGKILL =  ProcessSignal(io.ProcessSignal.sigkill);
+  static const ProcessSignal sigwinch = PosixProcessSignal(io.ProcessSignal.sigwinch);
+  static const ProcessSignal sigterm = PosixProcessSignal(io.ProcessSignal.sigterm);
+  static const ProcessSignal sigusr1 = PosixProcessSignal(io.ProcessSignal.sigusr1);
+  static const ProcessSignal sigusr2 = PosixProcessSignal(io.ProcessSignal.sigusr2);
+  static const ProcessSignal sigint = ProcessSignal(io.ProcessSignal.sigint);
+  static const ProcessSignal sigkill = ProcessSignal(io.ProcessSignal.sigkill);
 
   final io.ProcessSignal _delegate;
+  final Platform _platform;
 
   Stream<ProcessSignal> watch() {
     return _delegate.watch().map<ProcessSignal>((io.ProcessSignal signal) => this);
@@ -184,12 +185,12 @@ class ProcessSignal {
   ///
   /// Returns true if the signal was delivered, false otherwise.
   ///
-  /// On Windows, this can only be used with [ProcessSignal.SIGTERM], which
+  /// On Windows, this can only be used with [ProcessSignal.sigterm], which
   /// terminates the process.
   ///
   /// This is implemented by sending the signal using [Process.killPid].
   bool send(int pid) {
-    assert(!globals.platform.isWindows || this == ProcessSignal.SIGTERM);
+    assert(!_platform.isWindows || this == ProcessSignal.sigterm);
     return io.Process.killPid(pid, _delegate);
   }
 
@@ -200,13 +201,16 @@ class ProcessSignal {
 /// A [ProcessSignal] that is only available on Posix platforms.
 ///
 /// Listening to a [_PosixProcessSignal] is a no-op on Windows.
-class _PosixProcessSignal extends ProcessSignal {
+@visibleForTesting
+class PosixProcessSignal extends ProcessSignal {
 
-  const _PosixProcessSignal._(io.ProcessSignal wrappedSignal) : super(wrappedSignal);
+  const PosixProcessSignal(io.ProcessSignal wrappedSignal, {@visibleForTesting Platform platform = const LocalPlatform()})
+    : super(wrappedSignal, platform: platform);
 
   @override
   Stream<ProcessSignal> watch() {
-    if (globals.platform.isWindows) {
+    // This uses the real platform since it invokes dart:io functionality directly.
+    if (_platform.isWindows) {
       return const Stream<ProcessSignal>.empty();
     }
     return super.watch();
@@ -367,10 +371,9 @@ class Stdio {
 
 /// An overridable version of io.ProcessInfo.
 abstract class ProcessInfo {
-  factory ProcessInfo() => _DefaultProcessInfo(globals.fs);
-  factory ProcessInfo.test(FileSystem fs) => _TestProcessInfo(fs);
+  factory ProcessInfo(FileSystem fs) => _DefaultProcessInfo(fs);
 
-  static ProcessInfo get instance => context.get<ProcessInfo>();
+  factory ProcessInfo.test(FileSystem fs) => _TestProcessInfo(fs);
 
   int get currentRss;
 
@@ -379,8 +382,6 @@ abstract class ProcessInfo {
   File writePidFile(String pidFile);
 }
 
-ProcessInfo get processInfo => ProcessInfo.instance;
-
 /// The default implementation of [ProcessInfo], which uses [io.ProcessInfo].
 class _DefaultProcessInfo implements ProcessInfo {
   _DefaultProcessInfo(this._fileSystem);

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

@@ -24,8 +24,8 @@ abstract class Signals {
 
   // The default list of signals that should cause the process to exit.
   static const List<ProcessSignal> defaultExitSignals = <ProcessSignal>[
-    ProcessSignal.SIGTERM,
-    ProcessSignal.SIGINT,
+    ProcessSignal.sigterm,
+    ProcessSignal.sigint,
   ];
 
   /// Adds a signal handler to run on receipt of signal.

packages/flutter_tools/lib/src/commands/attach.dart

@@ -368,7 +368,7 @@ known, it can be explicitly provided to attach via the command-line, e.g.
             logger: globals.logger,
             terminal: globals.terminal,
             signals: globals.signals,
-            processInfo: processInfo,
+            processInfo: globals.processInfo,
             reportReady: boolArg('report-ready'),
             pidFile: stringArg('pid-file'),
           )

packages/flutter_tools/lib/src/commands/logs.dart

@@ -67,12 +67,12 @@ class LogsCommand extends FlutterCommand {
     );
 
     // When terminating, close down the log reader.
-    ProcessSignal.SIGINT.watch().listen((ProcessSignal signal) {
+    ProcessSignal.sigint.watch().listen((ProcessSignal signal) {
       subscription.cancel();
       globals.printStatus('');
       exitCompleter.complete(0);
     });
-    ProcessSignal.SIGTERM.watch().listen((ProcessSignal signal) {
+    ProcessSignal.sigterm.watch().listen((ProcessSignal signal) {
       subscription.cancel();
       exitCompleter.complete(0);
     });

packages/flutter_tools/lib/src/commands/run.dart

@@ -12,7 +12,6 @@ import 'package:vm_service/vm_service.dart';
 import '../android/android_device.dart';
 import '../base/common.dart';
 import '../base/file_system.dart';
-import '../base/io.dart';
 import '../base/utils.dart';
 import '../build_info.dart';
 import '../device.dart';
@@ -639,7 +638,7 @@ class RunCommand extends RunCommandBase {
             logger: globals.logger,
             terminal: globals.terminal,
             signals: globals.signals,
-            processInfo: processInfo,
+            processInfo: globals.processInfo,
             reportReady: boolArg('report-ready'),
             pidFile: stringArg('pid-file'),
           )

packages/flutter_tools/lib/src/context_runner.dart

@@ -286,7 +286,7 @@ Future<T> runInContext<T>(
         logger: globals.logger,
         platform: globals.platform,
       ),
-      ProcessInfo: () => ProcessInfo(),
+      ProcessInfo: () => ProcessInfo(globals.fs),
       ProcessManager: () => ErrorHandlingProcessManager(
         delegate: const LocalProcessManager(),
         platform: globals.platform,

packages/flutter_tools/lib/src/globals.dart

@@ -126,6 +126,8 @@ Future<bool> get isRunningOnBot => botDetector.isRunningOnBot;
 /// The current system clock instance.
 SystemClock get systemClock => context.get<SystemClock>();
 
+ProcessInfo get processInfo => context.get<ProcessInfo>();
+
 /// Display an error level message to the user. Commands should use this if they
 /// fail in some way.
 ///

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

@@ -209,7 +209,7 @@ class CommandResultEvent extends UsageEvent {
     // so that we can get the command result even if trying to grab maxRss
     // throws an exception.
     try {
-      final int maxRss = processInfo.maxRss;
+      final int maxRss = globals.processInfo.maxRss;
       flutterUsage.sendEvent(
         'tool-command-max-rss',
         category,

packages/flutter_tools/lib/src/resident_runner.dart

@@ -1501,11 +1501,11 @@ class TerminalHandler {
 
   void registerSignalHandlers() {
     assert(residentRunner.stayResident);
-    _addSignalHandler(io.ProcessSignal.SIGINT, _cleanUp);
-    _addSignalHandler(io.ProcessSignal.SIGTERM, _cleanUp);
+    _addSignalHandler(io.ProcessSignal.sigint, _cleanUp);
+    _addSignalHandler(io.ProcessSignal.sigterm, _cleanUp);
     if (residentRunner.supportsServiceProtocol && residentRunner.supportsRestart) {
-      _addSignalHandler(io.ProcessSignal.SIGUSR1, _handleSignal);
-      _addSignalHandler(io.ProcessSignal.SIGUSR2, _handleSignal);
+      _addSignalHandler(io.ProcessSignal.sigusr1, _handleSignal);
+      _addSignalHandler(io.ProcessSignal.sigusr2, _handleSignal);
       if (_pidFile != null) {
         _logger.printTrace('Writing pid to: $_pidFile');
         _actualPidFile = _processInfo.writePidFile(_pidFile);
@@ -1663,7 +1663,7 @@ class TerminalHandler {
     }
     _processingUserRequest = true;
 
-    final bool fullRestart = signal == io.ProcessSignal.SIGUSR2;
+    final bool fullRestart = signal == io.ProcessSignal.sigusr2;
 
     try {
       await residentRunner.restart(fullRestart: fullRestart);

packages/flutter_tools/lib/src/runner/flutter_command.dart

@@ -1075,8 +1075,8 @@ abstract class FlutterCommand extends Command<void> {
         globals.systemClock.now(),
       );
     }
-    globals.signals.addHandler(io.ProcessSignal.SIGTERM, handler);
-    globals.signals.addHandler(io.ProcessSignal.SIGINT, handler);
+    globals.signals.addHandler(io.ProcessSignal.sigterm, handler);
+    globals.signals.addHandler(io.ProcessSignal.sigint, handler);
   }
 
   /// Logs data about this command.

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

@@ -9,6 +9,7 @@ import 'dart:io' as io;
 
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/base/io.dart';
+import 'package:flutter_tools/src/base/platform.dart';
 import 'package:test/fake.dart';
 
 import '../../src/common.dart';
@@ -66,7 +67,7 @@ void main() {
   });
 
   testUsingContext('ProcessSignal toString() works', () async {
-    expect(io.ProcessSignal.sigint.toString(), ProcessSignal.SIGINT.toString());
+    expect(io.ProcessSignal.sigint.toString(), ProcessSignal.sigint.toString());
   });
 
   test('exit throws a StateError if called without being overriden', () {
@@ -100,6 +101,18 @@ void main() {
 
     resetNetworkInterfaceLister();
   });
+
+  testWithoutContext('Does not listen to Posix process signals on windows', () async {
+    final FakePlatform windows = FakePlatform(operatingSystem: 'windows');
+    final FakePlatform linux = FakePlatform(operatingSystem: 'linux');
+    final FakeProcessSignal fakeSignalA = FakeProcessSignal();
+    final FakeProcessSignal fakeSignalB = FakeProcessSignal();
+    fakeSignalA.controller.add(fakeSignalA);
+    fakeSignalB.controller.add(fakeSignalB);
+
+    expect(await PosixProcessSignal(fakeSignalA, platform: windows).watch().isEmpty, true);
+    expect(await PosixProcessSignal(fakeSignalB, platform: linux).watch().first, isNotNull);
+  });
 }
 
 class FakeProcessSignal extends Fake implements io.ProcessSignal {

packages/flutter_tools/test/general.shard/runner/flutter_command_test.dart

@@ -637,7 +637,7 @@ class FakeSignals implements Signals {
 
   @override
   Object addHandler(ProcessSignal signal, SignalHandler handler) {
-    if (signal == ProcessSignal.SIGTERM) {
+    if (signal == ProcessSignal.sigterm) {
       return delegate.addHandler(subForSigTerm, handler);
     }
     return delegate.addHandler(signal, handler);

packages/flutter_tools/test/integration.shard/test_driver.dart

@@ -204,7 +204,7 @@ abstract class FlutterTestDriver {
 
   Future<int> _killForcefully() {
     _debugPrint('Sending SIGKILL to $_processPid..');
-    ProcessSignal.SIGKILL.send(_processPid);
+    ProcessSignal.sigkill.send(_processPid);
     return _process.exitCode;
   }