Implemented autosave on a 5-second timer (#3037)

* Implemented autosave on a 5-second timer

* Documented

* Removed double quotes

* Use appModel instead of codeMirror

* Moved autosave functionality to LocalStorage singleton

* Added unit tests

* Fixed lints

* Dart format

* Use callback to get fallback snippet

* Dart format

* Test for more cases

* Removed local_storage conditional import

* Formatted

* Reverted async function to .then

* Got rid of _autosave() on dispose()

* Revert "Removed local_storage conditional import"

This reverts commit c952120.

pkgs/dartpad_ui/lib/editor/editor.dart

@@ -12,6 +12,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:web/web.dart' as web;
 
+import '../local_storage.dart';
 import '../model.dart';
 import 'codemirror.dart';
 
@@ -177,10 +178,17 @@ class _EditorWidgetState extends State<EditorWidget> implements EditorService {
   @override
   void initState() {
     super.initState();
-
+    _autosaveTimer = Timer.periodic(const Duration(seconds: 5), _autosave);
     widget.appModel.appReady.addListener(_updateEditableStatus);
   }
 
+  Timer? _autosaveTimer;
+  void _autosave([Timer? timer]) {
+    final content = widget.appModel.sourceCodeController.text;
+    if (content.isEmpty) return;
+    LocalStorage.instance.saveUserCode(content);
+  }
+
   void _platformViewCreated(int id, {required bool darkMode}) {
     codeMirror = codeMirrorInstance;
 
@@ -304,6 +312,7 @@ class _EditorWidgetState extends State<EditorWidget> implements EditorService {
   @override
   void dispose() {
     listener?.cancel();
+    _autosaveTimer?.cancel();
 
     widget.appServices.registerEditorService(null);
 

pkgs/dartpad_ui/lib/execution/frame.dart

@@ -62,7 +62,7 @@ function dartPrint(message) {
     'sender': 'frame',
     'type': 'stdout',
     'message': message.toString()
-  }, '*');  
+  }, '*');
 }
 ''');
 

pkgs/dartpad_ui/lib/local_storage.dart

@@ -0,0 +1,13 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'local_storage/stub.dart'
+    if (dart.library.js_util) 'local_storage/web.dart';
+
+abstract class LocalStorage {
+  static LocalStorage instance = LocalStorageImpl();
+
+  void saveUserCode(String code);
+  String? getUserCode();
+}

pkgs/dartpad_ui/lib/local_storage/stub.dart

@@ -0,0 +1,16 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import '../local_storage.dart';
+import '../utils.dart';
+
+class LocalStorageImpl extends LocalStorage {
+  String? _code;
+
+  @override
+  void saveUserCode(String code) => _code = code;
+
+  @override
+  String? getUserCode() => _code?.nullIfEmpty;
+}

pkgs/dartpad_ui/lib/local_storage/web.dart

@@ -0,0 +1,20 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:web/web.dart' as web;
+
+import '../local_storage.dart';
+import '../utils.dart';
+
+const _userInputKey = 'user_';
+
+class LocalStorageImpl extends LocalStorage {
+  @override
+  void saveUserCode(String code) =>
+      web.window.localStorage.setItem(_userInputKey, code);
+
+  @override
+  String? getUserCode() =>
+      web.window.localStorage.getItem(_userInputKey)?.nullIfEmpty;
+}

pkgs/dartpad_ui/lib/main.dart

@@ -23,6 +23,7 @@ import 'embed.dart';
 import 'execution/execution.dart';
 import 'extensions.dart';
 import 'keys.dart' as keys;
+import 'local_storage.dart';
 import 'model.dart';
 import 'problems.dart';
 import 'samples.g.dart';
@@ -274,19 +275,20 @@ class _DartPadMainPageState extends State<DartPadMainPage>
     appServices.populateVersions();
     appServices
         .performInitialLoad(
-            gistId: widget.gistId,
-            sampleId: widget.builtinSampleId,
-            flutterSampleId: widget.flutterSampleId,
-            channel: widget.initialChannel,
-            fallbackSnippet: Samples.defaultSnippet())
+      gistId: widget.gistId,
+      sampleId: widget.builtinSampleId,
+      flutterSampleId: widget.flutterSampleId,
+      channel: widget.initialChannel,
+      getFallback: () =>
+          LocalStorage.instance.getUserCode() ?? Samples.defaultSnippet(),
+    )
         .then((value) {
       // Start listening for inject code messages.
       handleEmbedMessage(appServices, runOnInject: widget.runOnLoad);
       if (widget.runOnLoad) {
         appServices.performCompileAndRun();
       }
     });
-
     appModel.compilingBusy.addListener(_handleRunStarted);
   }
 

pkgs/dartpad_ui/lib/model.dart

@@ -207,7 +207,7 @@ class AppServices {
     String? sampleId,
     String? flutterSampleId,
     String? channel,
-    required String fallbackSnippet,
+    required String Function() getFallback,
   }) async {
     // Delay a bit for codemirror to initialize.
     await Future<void>.delayed(const Duration(milliseconds: 1));
@@ -241,7 +241,7 @@ class AppServices {
 
         appModel.appendLineToConsole('Error loading sample: $e');
 
-        appModel.sourceCodeController.text = fallbackSnippet;
+        appModel.sourceCodeController.text = getFallback();
         appModel.appReady.value = true;
       } finally {
         loader.dispose();
@@ -265,7 +265,7 @@ class AppServices {
         final source = gist.mainDartSource;
         if (source == null) {
           appModel.editorStatus.showToast('main.dart not found');
-          appModel.sourceCodeController.text = fallbackSnippet;
+          appModel.sourceCodeController.text = getFallback();
         } else {
           appModel.sourceCodeController.text = source;
 
@@ -285,7 +285,7 @@ class AppServices {
 
         appModel.appendLineToConsole('Error loading gist: $e');
 
-        appModel.sourceCodeController.text = fallbackSnippet;
+        appModel.sourceCodeController.text = getFallback();
         appModel.appReady.value = true;
       } finally {
         gistLoader.dispose();
@@ -295,7 +295,7 @@ class AppServices {
     }
 
     // Neither gistId nor flutterSampleId were passed in.
-    appModel.sourceCodeController.text = fallbackSnippet;
+    appModel.sourceCodeController.text = getFallback();
     appModel.appReady.value = true;
   }
 

pkgs/dartpad_ui/lib/utils.dart

@@ -184,3 +184,7 @@ enum MessageState {
   showing,
   closing;
 }
+
+extension StringUtils on String {
+  String? get nullIfEmpty => isEmpty ? null : this;
+}

pkgs/dartpad_ui/test/autosave_test.dart

@@ -0,0 +1,128 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:dartpad_ui/local_storage.dart';
+import 'package:dartpad_ui/model.dart';
+import 'package:dartpad_ui/samples.g.dart';
+import 'package:dartpad_ui/utils.dart';
+
+import 'package:test/test.dart';
+
+String getFallback() =>
+    LocalStorage.instance.getUserCode() ?? Samples.defaultSnippet();
+
+Never throwingFallback() =>
+    throw StateError('DartPad tried to load the fallback');
+
+void main() {
+  const channel = Channel.stable;
+  group('Autosave:', () {
+    test('empty content is treated as null', () {
+      expect(''.nullIfEmpty, isNull);
+
+      LocalStorage.instance.saveUserCode('non-empty');
+      expect(LocalStorage.instance.getUserCode(), isNotNull);
+
+      LocalStorage.instance.saveUserCode('');
+      expect(LocalStorage.instance.getUserCode(), isNull);
+    });
+
+    test('null content means sample snippet is shown', () async {
+      final model = AppModel();
+      final services = AppServices(model, channel);
+      LocalStorage.instance.saveUserCode('');
+      expect(LocalStorage.instance.getUserCode(), isNull);
+
+      await services.performInitialLoad(
+        getFallback: getFallback,
+      );
+      expect(model.sourceCodeController.text, equals(Samples.defaultSnippet()));
+    });
+
+    group('non-null content is shown with', () {
+      const sample = 'Hello, World!';
+      setUp(() => LocalStorage.instance.saveUserCode(sample));
+
+      test('only fallback', () async {
+        final model = AppModel();
+        final services = AppServices(model, channel);
+        expect(LocalStorage.instance.getUserCode(), equals(sample));
+
+        await services.performInitialLoad(
+          getFallback: getFallback,
+        );
+        expect(model.sourceCodeController.text, equals(sample));
+      });
+
+      test('invalid sample ID', () async {
+        final model = AppModel();
+        final services = AppServices(model, channel);
+        expect(LocalStorage.instance.getUserCode(), equals(sample));
+
+        await services.performInitialLoad(
+          getFallback: getFallback,
+          sampleId: 'This is hopefully not a valid sample ID',
+        );
+        expect(model.sourceCodeController.text, equals(sample));
+      });
+
+      test('invalid Flutter sample ID', () async {
+        final model = AppModel();
+        final services = AppServices(model, channel);
+        expect(LocalStorage.instance.getUserCode(), equals(sample));
+
+        await services.performInitialLoad(
+          getFallback: getFallback,
+          flutterSampleId: 'This is hopefully not a valid sample ID',
+        );
+        expect(model.sourceCodeController.text, equals(sample));
+      });
+
+      test('invalid Gist ID', () async {
+        final model = AppModel();
+        final services = AppServices(model, channel);
+        expect(LocalStorage.instance.getUserCode(), equals(sample));
+
+        const gistId = 'This is hopefully not a valid Gist ID';
+        await services.performInitialLoad(
+          getFallback: getFallback,
+          gistId: gistId,
+        );
+        expect(model.sourceCodeController.text, equals(sample));
+      });
+    });
+
+    group('content is not shown with', () {
+      const sample = 'Hello, World!';
+      setUp(() => LocalStorage.instance.saveUserCode(sample));
+      // Not testing flutterSampleId to avoid breaking when the Flutter docs change
+
+      test('Gist', () async {
+        final model = AppModel();
+        final services = AppServices(model, channel);
+        expect(LocalStorage.instance.getUserCode(), equals(sample));
+
+        // From gists_tests.dart
+        const gistId = 'd3bd83918d21b6d5f778bdc69c3d36d6';
+        await services.performInitialLoad(
+          getFallback: throwingFallback,
+          gistId: gistId,
+        );
+        expect(model.sourceCodeController.text, isNot(equals(sample)));
+      });
+
+      test('sample', () async {
+        final model = AppModel();
+        final services = AppServices(model, channel);
+        expect(LocalStorage.instance.getUserCode(), equals(sample));
+
+        await services.performInitialLoad(
+          getFallback: throwingFallback,
+          sampleId: 'dart',
+        );
+        expect(model.sourceCodeController.text, isNot(equals(sample)));
+      });
+    });
+  });
+}