feat(binding/dart): add examples, tests (#5740)

* add examples, tests

* re-export file

* typo

* add license header

* typo

.github/workflows/ci_bindings_dart.yml

@@ -76,5 +76,4 @@ jobs:
       - name: test
         working-directory: bindings/dart
         run: |
-          dart run lib/opendal_test.dart
-
+          dart run tests/opendal_test.dart

bindings/dart/README.md

@@ -1,16 +1,60 @@
 # Apache OpenDAL™ Dart Binding (WIP)
 
+## Useful Links
+
+- [Examples](./examples)
+
+## Usage
+
+Api is designed to be like stdlib style.
+
+This is stdlib
+
+```
+import 'dart:io';
+
+void main() async {
+  final file = File('file.txt');
+  var is_exists = await file.exists();
+  print(is_exists);
+}
+```
+
+This is opendal
+
+```
+import 'opendal.dart';
+
+void main() async {
+  await RustLib.init();
+  final File = FileManager.initOp(schemeStr: "fs", map: {"root": "/tmp"});
+  // drop-in
+  final file = File('file.txt');
+  var is_exists = await file.exists();
+  print(is_exists);
+}
+
+```
+
+## Test
+
+```
+dart run tests/opendal_test.dart
+```
+
 ## Development
 
 ```
 flutter pub get
 flutter_rust_bridge_codegen generate
 cd rust
 cargo build -r
-cd ..
-dart run lib/opendal_test.dart
 ```
 
+## Update generated code
+
+This binding uses <https://github.com/fzyzcjy/flutter_rust_bridge>, when updating the codegen. First check `FLUTTER_RUST_BRIDGE_CODEGEN_VERSION`, then pin the version of `flutter_rust_bridge` in `pubspec.yaml` and `rust/Cargo.toml`. Make sure the runtime versions are matched.
+
 ## License and Trademarks
 
 Licensed under the Apache License, Version 2.0: http://www.apache.org/licenses/LICENSE-2.0

bindings/dart/examples/basic.dart

@@ -0,0 +1,26 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+import '../lib/opendal.dart';
+
+void main() async {
+  await RustLib.init();
+  final File = FileManager.initOp(schemeStr: "fs", map: {"root": "/tmp"});
+  // drop-in style 
+  var testFile = File("test_1.txt");
+  assert(!(await testFile.exists()));
+}

bindings/dart/lib/opendal.dart

@@ -1,5 +1,24 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
 import 'src/rust/frb_generated.dart';
 import 'src/rust/api/opendal_api.dart';
+export 'src/rust/frb_generated.dart';
+export 'src/rust/api/opendal_api.dart';
 
 class FileManager {
   final Operator _operator;

bindings/dart/lib/opendal_test.dart → bindings/dart/tests/opendal_test.dart

@@ -1,7 +1,5 @@
 import 'package:test/test.dart';
-import 'src/rust/frb_generated.dart';
-import 'src/rust/api/opendal_api.dart';
-import 'opendal.dart';
+import '../lib/opendal.dart';
 
 void main() {
   group('opendal unit test', () {