[path_provider] add getApplicationSupportDirectory (flutter#1566)

* Add support for getApplicationLibraryDirectory

packages/path_provider/CHANGELOG.md

@@ -1,3 +1,13 @@
+## 1.1.0
+
+* Added `getApplicationSupportDirectory`.
+* Updated documentation for `getApplicationDocumentsDirectory` to suggest
+  using `getApplicationSupportDirectory` on iOS and
+  `getExternalStorageDirectory` on Android.
+* Updated documentation for `getTemporaryDirectory` to suggest using it
+  for caches of files that do not need to be backed up.
+* Updated integration tests and example to reflect the above changes.
+
 ## 1.0.0
 
 * Added integration tests.

packages/path_provider/example/lib/main.dart

@@ -35,6 +35,7 @@ class MyHomePage extends StatefulWidget {
 
 class _MyHomePageState extends State<MyHomePage> {
   Future<Directory> _tempDirectory;
+  Future<Directory> _appSupportDirectory;
   Future<Directory> _appDocumentsDirectory;
   Future<Directory> _externalDocumentsDirectory;
 
@@ -65,6 +66,12 @@ class _MyHomePageState extends State<MyHomePage> {
     });
   }
 
+  void _requestAppSupportDirectory() {
+    setState(() {
+      _appSupportDirectory = getApplicationSupportDirectory();
+    });
+  }
+
   void _requestExternalStorageDirectory() {
     setState(() {
       _externalDocumentsDirectory = getExternalStorageDirectory();
@@ -111,6 +118,21 @@ class _MyHomePageState extends State<MyHomePage> {
               child: FutureBuilder<Directory>(
                   future: _appDocumentsDirectory, builder: _buildDirectory),
             ),
+            Column(
+              children: <Widget>[
+                Padding(
+                  padding: const EdgeInsets.all(16.0),
+                  child: RaisedButton(
+                    child: const Text('Get Application Support Directory'),
+                    onPressed: _requestAppSupportDirectory,
+                  ),
+                ),
+              ],
+            ),
+            Expanded(
+              child: FutureBuilder<Directory>(
+                  future: _appSupportDirectory, builder: _buildDirectory),
+            ),
             Column(children: <Widget>[
               Padding(
                 padding: const EdgeInsets.all(16.0),

packages/path_provider/example/test_driver/path_provider.dart

@@ -35,6 +35,21 @@ void main() {
     file.deleteSync();
   });
 
+  test('getApplicationSupportDirectory', () async {
+    if (Platform.isIOS) {
+      final Directory result = await getApplicationSupportDirectory();
+      final String uuid = Uuid().v1();
+      final File file = File('${result.path}/$uuid.txt');
+      file.writeAsStringSync('Hello world!');
+      expect(file.readAsStringSync(), 'Hello world!');
+      expect(result.listSync(), isNotEmpty);
+      file.deleteSync();
+    } else if (Platform.isAndroid) {
+      final Future<Directory> result = getApplicationSupportDirectory();
+      expect(result, throwsA(isInstanceOf<UnsupportedError>()));
+    }
+  });
+
   test('getExternalStorageDirectory', () async {
     if (Platform.isIOS) {
       final Future<Directory> result = getExternalStorageDirectory();

packages/path_provider/ios/Classes/PathProviderPlugin.m

@@ -9,6 +9,13 @@
   return paths.firstObject;
 }
 
+static FlutterError* getFlutterError(NSError* error) {
+  if (error == nil) return nil;
+  return [FlutterError errorWithCode:[NSString stringWithFormat:@"Error %ld", error.code]
+                             message:error.domain
+                             details:error.localizedDescription];
+}
+
 @implementation FLTPathProviderPlugin
 
 + (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar>*)registrar {
@@ -20,6 +27,21 @@ + (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar>*)registrar {
       result([self getTemporaryDirectory]);
     } else if ([@"getApplicationDocumentsDirectory" isEqualToString:call.method]) {
       result([self getApplicationDocumentsDirectory]);
+    } else if ([@"getApplicationSupportDirectory" isEqualToString:call.method]) {
+      NSString* path = [self getApplicationSupportDirectory];
+
+      // Create the path if it doesn't exist
+      NSError* error;
+      NSFileManager* fileManager = [NSFileManager defaultManager];
+      BOOL success = [fileManager createDirectoryAtPath:path
+                            withIntermediateDirectories:YES
+                                             attributes:nil
+                                                  error:&error];
+      if (!success) {
+        result(getFlutterError(error));
+      } else {
+        result(path);
+      }
     } else {
       result(FlutterMethodNotImplemented);
     }
@@ -34,4 +56,8 @@ + (NSString*)getApplicationDocumentsDirectory {
   return GetDirectoryOfType(NSDocumentDirectory);
 }
 
++ (NSString*)getApplicationSupportDirectory {
+  return GetDirectoryOfType(NSApplicationSupportDirectory);
+}
+
 @end

packages/path_provider/lib/path_provider.dart

@@ -10,7 +10,8 @@ import 'package:flutter/services.dart';
 const MethodChannel _channel =
     MethodChannel('plugins.flutter.io/path_provider');
 
-/// Path to the temporary directory on the device.
+/// Path to the temporary directory on the device that is not backed up and is
+/// suitable for storing caches of downloaded files.
 ///
 /// Files in this directory may be cleared at any time. This does *not* return
 /// a new temporary directory. Instead, the caller is responsible for creating
@@ -21,29 +22,47 @@ const MethodChannel _channel =
 ///
 /// On Android, this uses the `getCacheDir` API on the context.
 Future<Directory> getTemporaryDirectory() async {
-  // TODO(amirh): remove this on when the invokeMethod update makes it to stable Flutter.
-  // https://github.com/flutter/flutter/issues/26431
-  // ignore: strong_mode_implicit_dynamic_method
-  final String path = await _channel.invokeMethod('getTemporaryDirectory');
+  final String path =
+      await _channel.invokeMethod<String>('getTemporaryDirectory');
+  if (path == null) {
+    return null;
+  }
+  return Directory(path);
+}
+
+/// Path to a directory where the application may place application support
+/// files.
+///
+/// Use this for files you don’t want exposed to the user. Your app should not
+/// use this directory for user data files.
+///
+/// On iOS, this uses the `NSApplicationSupportDirectory` API.
+/// If this directory does not exist, it is created automatically.
+///
+/// On Android, this function throws an [UnsupportedError].
+Future<Directory> getApplicationSupportDirectory() async {
+  if (!Platform.isIOS)
+    throw UnsupportedError("getApplicationSupportDirectory requires iOS");
+  final String path =
+      await _channel.invokeMethod<String>('getApplicationSupportDirectory');
   if (path == null) {
     return null;
   }
   return Directory(path);
 }
 
-/// Path to a directory where the application may place files that are private
-/// to the application and will only be cleared when the application itself
-/// is deleted.
+/// Path to a directory where the application may place data that is
+/// user-generated, or that cannot otherwise be recreated by your application.
 ///
-/// On iOS, this uses the `NSDocumentsDirectory` API.
+/// On iOS, this uses the `NSDocumentDirectory` API. Consider using
+/// [getApplicationSupportDirectory] instead if the data is not user-generated.
 ///
-/// On Android, this returns the AppData directory.
+/// On Android, this uses the `getDataDirectory` API on the context. Consider
+/// using getExternalStorageDirectory instead if data is intended to be visible
+/// to the user.
 Future<Directory> getApplicationDocumentsDirectory() async {
   final String path =
-      // TODO(amirh): remove this on when the invokeMethod update makes it to stable Flutter.
-      // https://github.com/flutter/flutter/issues/26431
-      // ignore: strong_mode_implicit_dynamic_method
-      await _channel.invokeMethod('getApplicationDocumentsDirectory');
+      await _channel.invokeMethod<String>('getApplicationDocumentsDirectory');
   if (path == null) {
     return null;
   }
@@ -54,17 +73,15 @@ Future<Directory> getApplicationDocumentsDirectory() async {
 /// The current operating system should be determined before issuing this
 /// function call, as this functionality is only available on Android.
 ///
-/// On iOS, this function throws an UnsupportedError as it is not possible
+/// On iOS, this function throws an [UnsupportedError] as it is not possible
 /// to access outside the app's sandbox.
 ///
-/// On Android this returns getExternalStorageDirectory.
+/// On Android this uses the `getExternalStorageDirectory` API.
 Future<Directory> getExternalStorageDirectory() async {
   if (Platform.isIOS)
     throw UnsupportedError("Functionality not available on iOS");
-  // TODO(amirh): remove this on when the invokeMethod update makes it to stable Flutter.
-  // https://github.com/flutter/flutter/issues/26431
-  // ignore: strong_mode_implicit_dynamic_method
-  final String path = await _channel.invokeMethod('getStorageDirectory');
+  final String path =
+      await _channel.invokeMethod<String>('getStorageDirectory');
   if (path == null) {
     return null;
   }

packages/path_provider/pubspec.yaml

@@ -3,7 +3,7 @@ description: Flutter plugin for getting commonly used locations on the Android &
   iOS file systems, such as the temp and app data directories.
 author: Flutter Team <flutter-dev@googlegroups.com>
 homepage: https://github.com/flutter/plugins/tree/master/packages/path_provider
-version: 1.0.0
+version: 1.1.0
 
 flutter:
   plugin: