Support iOS screenshot 1/2 (#8210)

* Support iOS screenshot 1/3

* Use path.join

* use fs.path instead

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

@@ -44,6 +44,7 @@ class IOSDevice extends Device {
     _iproxyPath = _checkForCommand('iproxy');
     _debuggerPath = _checkForCommand('idevicedebug');
     _loggerPath = _checkForCommand('idevicesyslog');
+    _screenshotPath = _checkForCommand('idevicescreenshot');
     _pusherPath = _checkForCommand(
         'ios-deploy',
         'To copy files to iOS devices, please install ios-deploy. '
@@ -70,6 +71,9 @@ class IOSDevice extends Device {
   String _loggerPath;
   String get loggerPath => _loggerPath;
 
+  String _screenshotPath;
+  String get screenshotPath => _screenshotPath;
+
   String _pusherPath;
   String get pusherPath => _pusherPath;
 
@@ -118,23 +122,21 @@ class IOSDevice extends Device {
     return runSync(<String>[informerPath, '-k', infoKey, '-u', deviceID]).trim();
   }
 
-  static final Map<String, String> _commandMap = <String, String>{};
   static String _checkForCommand(
     String command, [
     String macInstructions = _ideviceinstallerInstructions
   ]) {
-    return _commandMap.putIfAbsent(command, () {
-      try {
-        command = runCheckedSync(<String>['which', command]).trim();
-      } catch (e) {
-        if (p.platform.isMacOS) {
-          printError('$command not found. $macInstructions');
-        } else {
-          printError('Cannot control iOS devices or simulators. $command is not available on your platform.');
-        }
+    try {
+      command = runCheckedSync(<String>['which', command]).trim();
+    } catch (e) {
+      if (p.platform.isMacOS) {
+        printError('$command not found. $macInstructions');
+      } else {
+        printError('Cannot control iOS devices or simulators. $command is not available on your platform.');
       }
-      return command;
-    });
+      return null;
+    }
+    return command;
   }
 
   @override
@@ -364,14 +366,12 @@ class IOSDevice extends Device {
   }
 
   @override
-  bool get supportsScreenshot => false;
+  bool get supportsScreenshot => screenshotPath != null && screenshotPath.isNotEmpty;
 
   @override
   Future<Null> takeScreenshot(File outputFile) {
-    // We could use idevicescreenshot here (installed along with the brew
-    // ideviceinstaller tools). It however requires a developer disk image on
-    // the device.
-    return new Future<Null>.error('Taking screenshots is not supported on iOS devices. Consider using a simulator instead.');
+    runCheckedSync(<String>[screenshotPath, outputFile.path]);
+    return new Future<Null>.value();
   }
 }
 

packages/flutter_tools/test/src/ios/devices_test.dart

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io' show ProcessResult;
+import 'package:file/file.dart';
+import 'package:flutter_tools/src/base/file_system.dart';
+import 'package:flutter_tools/src/ios/devices.dart';
+
+import 'package:mockito/mockito.dart';
+import 'package:process/process.dart';
+import 'package:test/test.dart';
+
+import '../context.dart';
+class MockProcessManager extends Mock implements ProcessManager {}
+class MockFile extends Mock implements File {}
+
+void main() {
+  group('test screenshot', () {
+    MockProcessManager mockProcessManager;
+    MockFile mockOutputFile;
+    IOSDevice iosDeviceUnderTest;
+
+    setUp(() {
+      mockProcessManager = new MockProcessManager();
+      mockOutputFile = new MockFile();
+    });
+
+    testUsingContext(
+      'screenshot without ideviceinstaller error',
+      () async {
+        when(mockOutputFile.path).thenReturn(fs.path.join('some', 'test', 'path', 'image.png'));
+        // Let everything else return exit code 0 so process.dart doesn't crash.
+        // The matcher order is important.
+        when(
+          mockProcessManager.runSync(any, environment: null, workingDirectory:  null)
+        ).thenReturn(
+          new ProcessResult(2, 0, '', null)
+        );
+        // Let `which idevicescreenshot` fail with exit code 1.
+        when(
+          mockProcessManager.runSync(
+            <String>['which', 'idevicescreenshot'], environment: null, workingDirectory: null)
+        ).thenReturn(
+          new ProcessResult(1, 1, '', null)
+        );
+
+        iosDeviceUnderTest = new IOSDevice('1234');
+        iosDeviceUnderTest.takeScreenshot(mockOutputFile);
+        verify(mockProcessManager.runSync(
+          <String>['which', 'idevicescreenshot'], environment: null, workingDirectory: null));
+        verifyNever(mockProcessManager.runSync(
+          <String>['idevicescreenshot', fs.path.join('some', 'test', 'path', 'image.png')],
+          environment: null,
+          workingDirectory: null
+        ));
+        expect(testLogger.errorText, contains('brew install ideviceinstaller'));
+      },
+      overrides: <Type, Generator>{ProcessManager: () => mockProcessManager}
+    );
+
+    testUsingContext(
+      'screenshot with ideviceinstaller gets command',
+      () async {
+        when(mockOutputFile.path).thenReturn(fs.path.join('some', 'test', 'path', 'image.png'));
+        // Let everything else return exit code 0.
+        // The matcher order is important.
+        when(
+          mockProcessManager.runSync(any, environment: null, workingDirectory:  null)
+        ).thenReturn(
+          new ProcessResult(4, 0, '', null)
+        );
+        // Let there be idevicescreenshot in the PATH.
+        when(
+          mockProcessManager.runSync(
+            <String>['which', 'idevicescreenshot'], environment: null, workingDirectory: null)
+        ).thenReturn(
+          new ProcessResult(3, 0, fs.path.join('some', 'path', 'to', 'iscreenshot'), null)
+        );
+
+        iosDeviceUnderTest = new IOSDevice('1234');
+        iosDeviceUnderTest.takeScreenshot(mockOutputFile);
+        verify(mockProcessManager.runSync(
+          <String>['which', 'idevicescreenshot'], environment: null, workingDirectory: null));
+        verify(mockProcessManager.runSync(
+          <String>[
+            fs.path.join('some', 'path', 'to', 'iscreenshot'),
+            fs.path.join('some', 'test', 'path', 'image.png')
+          ],
+          environment: null,
+          workingDirectory: null
+        ));
+      },
+      overrides: <Type, Generator>{ProcessManager: () => mockProcessManager}
+    );
+  });
+}

packages/flutter_tools/test/src/ios/simulators_test.dart

 import 'dart:io' show ProcessResult;
 
 import 'package:file/file.dart';
+import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/ios/mac.dart';
 import 'package:flutter_tools/src/ios/simulators.dart';
 import 'package:mockito/mockito.dart';
@@ -122,7 +123,7 @@ void main() {
         when(mockXcode.xcodeMinorVersion).thenReturn(1);
         expect(deviceUnderTest.supportsScreenshot, false);
       },
-      overrides: <Type, Generator>{ Xcode: () => mockXcode }
+      overrides: <Type, Generator>{Xcode: () => mockXcode}
     );
 
     testUsingContext(
@@ -132,7 +133,7 @@ void main() {
         when(mockXcode.xcodeMinorVersion).thenReturn(2);
         expect(deviceUnderTest.supportsScreenshot, true);
         MockFile mockFile = new MockFile();
-        when(mockFile.path).thenReturn('/some/path/to/screenshot.png');
+        when(mockFile.path).thenReturn(fs.path.join('some', 'path', 'to', 'screenshot.png'));
         deviceUnderTest.takeScreenshot(mockFile);
         verify(mockProcessManager.runSync(
           <String>[
@@ -141,7 +142,7 @@ void main() {
               'io',
               'booted',
               'screenshot',
-              '/some/path/to/screenshot.png'
+              fs.path.join('some', 'path', 'to', 'screenshot.png'),
           ],
           environment: null,
           workingDirectory: null