Migrate to os_log for reading iOS simulator logs (#12079)

1. Migrate simulator device log tailing to os_log toolchain
2. When the log tag (component) is available (iOS 11/Xcode 9), filter to
   the set of log lines with tag 'Flutter'.

As of iOS 11 / Xcode 9, Flutter engine logs are no longer recorded in the
simulator's syslog file, which we previously read using tail -f. Instead
they're now accessible through Apple's new macOS/iOS os_log facility,
via /usr/bin/log, which supports a relatively flexible query language.

When run in non-interactive mode, /usr/bin/log buffers its output in 4k
chunks, which is significantly smaller than what's emitted up to the
point where the observatory/diagnostics port information is logged. As a
workaround we force it to run in interactive mode via the script tool.

packages/flutter_tools/lib/src/ios/simulators.dart

@@ -486,6 +486,36 @@ class IOSSimulator extends Device {
   }
 }
 
+final RegExp _iosSdkRegExp = new RegExp(r'iOS (\d+)');
+
+/// Launches the device log reader process on the host.
+Future<Process> launchDeviceLogTool(IOSSimulator device) async {
+  final Match sdkMatch = _iosSdkRegExp.firstMatch(await device.sdkNameAndVersion);
+  final int majorVersion = int.parse(sdkMatch.group(1) ?? 11);
+
+  // Versions of iOS prior to iOS 11 log to the simulator syslog file.
+  if (majorVersion < 11)
+    return runCommand(<String>['tail', '-n', '0', '-F', device.logFilePath]);
+
+  // For iOS 11 and above, use /usr/bin/log to tail process logs.
+  // Run in interactive mode (via script), otherwise /usr/bin/log buffers in 4k chunks. (radar: 34420207)
+  return runCommand(<String>[
+    'script', '/dev/null', '/usr/bin/log', 'stream', '--style', 'syslog', '--predicate', 'processImagePath CONTAINS "${device.id}"',
+  ]);
+}
+
+Future<Process> launchSystemLogTool(IOSSimulator device) async {
+  final Match sdkMatch = _iosSdkRegExp.firstMatch(await device.sdkNameAndVersion);
+  final int majorVersion = int.parse(sdkMatch.group(1) ?? 11);
+
+  // Versions of iOS prior to 11 tail the simulator syslog file.
+  if (majorVersion < 11)
+    return runCommand(<String>['tail', '-n', '0', '-F', '/private/var/log/system.log']);
+
+  // For iOS 11 and later, all relevant detail is in the device log.
+  return null;
+}
+
 class _IOSSimulatorLogReader extends DeviceLogReader {
   String _appName;
 
@@ -514,15 +544,17 @@ class _IOSSimulatorLogReader extends DeviceLogReader {
   Future<Null> _start() async {
     // Device log.
     device.ensureLogsExists();
-    _deviceProcess = await runCommand(<String>['tail', '-n', '0', '-F', device.logFilePath]);
+    _deviceProcess = await launchDeviceLogTool(device);
     _deviceProcess.stdout.transform(UTF8.decoder).transform(const LineSplitter()).listen(_onDeviceLine);
     _deviceProcess.stderr.transform(UTF8.decoder).transform(const LineSplitter()).listen(_onDeviceLine);
 
     // Track system.log crashes.
     // ReportCrash[37965]: Saved crash report for FlutterRunner[37941]...
-    _systemProcess = await runCommand(<String>['tail', '-n', '0', '-F', '/private/var/log/system.log']);
-    _systemProcess.stdout.transform(UTF8.decoder).transform(const LineSplitter()).listen(_onSystemLine);
-    _systemProcess.stderr.transform(UTF8.decoder).transform(const LineSplitter()).listen(_onSystemLine);
+    _systemProcess = await launchSystemLogTool(device);
+    if (_systemProcess != null) {
+      _systemProcess.stdout.transform(UTF8.decoder).transform(const LineSplitter()).listen(_onSystemLine);
+      _systemProcess.stderr.transform(UTF8.decoder).transform(const LineSplitter()).listen(_onSystemLine);
+    }
 
     _deviceProcess.exitCode.whenComplete(() {
       if (_linesController.hasListener)
@@ -531,8 +563,9 @@ class _IOSSimulatorLogReader extends DeviceLogReader {
   }
 
   // Match the log prefix (in order to shorten it):
-  //   'Jan 29 01:31:44 devoncarew-macbookpro3 SpringBoard[96648]: ...'
-  static final RegExp _mapRegex = new RegExp(r'\S+ +\S+ +\S+ \S+ (.+)\[\d+\]\)?: (.*)$');
+  // * Xcode 8: Sep 13 15:28:51 cbracken-macpro localhost Runner[37195]: (Flutter) Observatory listening on http://127.0.0.1:57701/
+  // * Xcode 9: 2017-09-13 15:26:57.228948-0700  localhost Runner[37195]: (Flutter) Observatory listening on http://127.0.0.1:57701/
+  static final RegExp _mapRegex = new RegExp(r'\S+ +\S+ +\S+ +(\S+ +)?(\S+)\[\d+\]\)?: (\(.*\))? *(.*)$');
 
   // Jan 31 19:23:28 --- last message repeated 1 time ---
   static final RegExp _lastMessageSingleRegex = new RegExp(r'\S+ +\S+ +\S+ --- last message repeated 1 time ---$');
@@ -540,46 +573,29 @@ class _IOSSimulatorLogReader extends DeviceLogReader {
 
   static final RegExp _flutterRunnerRegex = new RegExp(r' FlutterRunner\[\d+\] ');
 
-  /// List of log categories to always show in the logs, even if this is an app-specific
-  /// [DeviceLogReader]. Add to this list to make the log output more verbose.
-  static final List<String> _whitelistedLogCategories = <String>[
-    'CoreSimulatorBridge',
-  ];
-
   String _filterDeviceLine(String string) {
     final Match match = _mapRegex.matchAsPrefix(string);
     if (match != null) {
-      final String category = match.group(1);
-      final String content = match.group(2);
+      final String category = match.group(2);
+      final String tag = match.group(3);
+      final String content = match.group(4);
 
-      // Filter out some messages that clearly aren't related to Flutter.
-      if (string.contains(': could not find icon for representation -> com.apple.'))
+      // Filter out non-Flutter originated noise from the engine.
+      if (category != 'Runner')
         return null;
 
-      if (category == 'CoreSimulatorBridge'
-          && content.startsWith('Pasteboard change listener callback port'))
+      if (tag != null && tag != '(Flutter)')
         return null;
 
-      if (category == 'routined'
-          && content.startsWith('CoreLocation: Error occurred while trying to retrieve motion state update'))
-        return null;
-
-      if (category == 'syslogd' && content == 'ASL Sender Statistics')
+      // Filter out some messages that clearly aren't related to Flutter.
+      if (string.contains(': could not find icon for representation -> com.apple.'))
         return null;
 
-      // assertiond: assertion failed: 15E65 13E230: assertiond + 15801 [3C808658-78EC-3950-A264-79A64E0E463B]: 0x1
-      if (category == 'assertiond'
-          && content.startsWith('assertion failed: ')
-          && content.endsWith(']: 0x1'))
-         return null;
-
       // assertion failed: 15G1212 13E230: libxpc.dylib + 57882 [66C28065-C9DB-3C8E-926F-5A40210A6D1B]: 0x7d
-      if (category == 'Runner'
-          && content.startsWith('assertion failed: ')
-          && content.contains(' libxpc.dylib '))
+      if (content.startsWith('assertion failed: ') && content.contains(' libxpc.dylib '))
         return null;
 
-      if (_appName == null || _whitelistedLogCategories.contains(category))
+      if (_appName == null)
         return '$category: $content';
       else if (category == _appName)
         return content;
@@ -587,6 +603,12 @@ class _IOSSimulatorLogReader extends DeviceLogReader {
       return null;
     }
 
+    if (string.startsWith('Filtering the log data using '))
+      return null;
+
+    if (string.startsWith('Timestamp                       (process)[PID]'))
+      return null;
+
     if (_lastMessageSingleRegex.matchAsPrefix(string) != null)
       return null;
 

packages/flutter_tools/test/ios/simulators_test.dart

 import 'dart:async';
-import 'dart:io' show ProcessResult;
+import 'dart:io' show ProcessResult, Process;
 
 import 'package:file/file.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
@@ -15,6 +15,7 @@ import '../src/context.dart';
 class MockXcode extends Mock implements Xcode {}
 class MockFile extends Mock implements File {}
 class MockProcessManager extends Mock implements ProcessManager {}
+class MockProcess extends Mock implements Process {}
 
 void main() {
   final FakePlatform osx = new FakePlatform.fromPlatform(const LocalPlatform());
@@ -177,4 +178,69 @@ void main() {
       }
     );
   });
+
+  group('launchDeviceLogTool', () {
+    MockProcessManager mockProcessManager;
+
+    setUp(() {
+      mockProcessManager = new MockProcessManager();
+      when(mockProcessManager.start(any, environment: null, workingDirectory: null))
+        .thenReturn(new Future<Process>.value(new MockProcess()));
+    });
+
+    testUsingContext('uses tail on iOS versions prior to iOS 11', () async {
+      final IOSSimulator device = new IOSSimulator('x', name: 'iPhone SE', category: 'iOS 9.3');
+      await launchDeviceLogTool(device);
+      expect(
+        verify(mockProcessManager.start(captureAny, environment: null, workingDirectory: null)).captured.single,
+        contains('tail'),
+      );
+    },
+    overrides: <Type, Generator>{
+      ProcessManager: () => mockProcessManager,
+    });
+
+    testUsingContext('uses /usr/bin/log on iOS 11 and above', () async {
+      final IOSSimulator device = new IOSSimulator('x', name: 'iPhone SE', category: 'iOS 11.0');
+      await launchDeviceLogTool(device);
+      expect(
+        verify(mockProcessManager.start(captureAny, environment: null, workingDirectory: null)).captured.single,
+        contains('/usr/bin/log'),
+      );
+    },
+    overrides: <Type, Generator>{
+      ProcessManager: () => mockProcessManager,
+    });
+  });
+
+  group('launchSystemLogTool', () {
+    MockProcessManager mockProcessManager;
+
+    setUp(() {
+      mockProcessManager = new MockProcessManager();
+      when(mockProcessManager.start(any, environment: null, workingDirectory: null))
+        .thenReturn(new Future<Process>.value(new MockProcess()));
+    });
+
+    testUsingContext('uses tail on iOS versions prior to iOS 11', () async {
+      final IOSSimulator device = new IOSSimulator('x', name: 'iPhone SE', category: 'iOS 9.3');
+      await launchSystemLogTool(device);
+      expect(
+        verify(mockProcessManager.start(captureAny, environment: null, workingDirectory: null)).captured.single,
+        contains('tail'),
+      );
+    },
+    overrides: <Type, Generator>{
+      ProcessManager: () => mockProcessManager,
+    });
+
+    testUsingContext('uses /usr/bin/log on iOS 11 and above', () async {
+      final IOSSimulator device = new IOSSimulator('x', name: 'iPhone SE', category: 'iOS 11.0');
+      await launchSystemLogTool(device);
+      verifyNever(mockProcessManager.start(any, environment: null, workingDirectory: null));
+    },
+    overrides: <Type, Generator>{
+      ProcessManager: () => mockProcessManager,
+    });
+  });
 }