Add support for download function in web

dio/lib/src/options.dart

@@ -41,6 +41,13 @@ enum ResponseType {
 
   /// Get the original bytes, the [Response.data] will be [List<int>].
   bytes,
+
+  /// Get blob url.
+  /// This value is needed when you need content in the form of a blob url.
+  /// Only work in web.
+  ///
+  /// the [Response.data] will be [String].
+  blobUrl,
 }
 
 /// {@template dio.options.ListFormat}

example_flutter_app/lib/download_web/download_blob.dart

@@ -0,0 +1,14 @@
+import 'dart:js_interop';
+import 'package:web/web.dart';
+
+void downloadBlob(String blobUrl, String name) {
+  final Document htmlDocument = document;
+  final HTMLAnchorElement anchor =
+      htmlDocument.createElement('a') as HTMLAnchorElement;
+  anchor.href = blobUrl;
+  anchor.style.display = name;
+  anchor.download = name;
+  document.body!.add(anchor);
+  anchor.click();
+  anchor.remove();
+}

example_flutter_app/lib/download_web/main_web_download.dart

@@ -0,0 +1,103 @@
+import 'package:dio/dio.dart';
+import 'package:flutter/material.dart';
+
+import 'download_blob.dart';
+
+late Dio dio;
+
+void main() {
+  dio = Dio(
+    BaseOptions(
+      connectTimeout: const Duration(hours: 3),
+    ),
+  );
+
+  dio.interceptors.add(LogInterceptor());
+  runApp(MyApp());
+}
+
+class MyApp extends StatelessWidget {
+  // This widget is the root of your application.
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      title: 'Flutter web download blob Demo',
+      theme: ThemeData(
+        primarySwatch: Colors.blue,
+      ),
+      home: MyHomePage(title: 'Flutter web download blob Demo'),
+    );
+  }
+}
+
+class MyHomePage extends StatefulWidget {
+  MyHomePage({
+    super.key,
+    this.title = '',
+  });
+
+  final String title;
+
+  @override
+  State<MyHomePage> createState() => _MyHomePageState();
+}
+
+class _MyHomePageState extends State<MyHomePage> {
+  var url =
+      'https://jsoncompare.org/LearningContainer/SampleFiles/Video/MP4/sample-mp4-file.mp4';
+
+  CancelToken cancelToken = CancelToken();
+
+  @override
+  void initState() {
+    super.initState();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: Text(widget.title),
+      ),
+      body: Center(
+        child: Column(
+          spacing: 20,
+          children: [
+            ElevatedButton(
+              child: const Text('Request'),
+              onPressed: () async {
+                if (cancelToken.isCancelled) {
+                  cancelToken = CancelToken();
+                }
+
+                try {
+                  // Fetch blob
+                  final Response res = await dio.download(
+                    url,
+                    '',
+                    onReceiveProgress: (count, total) {
+                      print((count / total) * 100);
+                    },
+                    cancelToken: cancelToken,
+                  );
+
+                  // Download blob
+                  downloadBlob(res.data, url.split('/').last);
+                  print('fin');
+                } catch (e) {
+                  print('error');
+                }
+              },
+            ),
+            ElevatedButton(
+              child: const Text('Cancel'),
+              onPressed: () async {
+                cancelToken.cancel();
+              },
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}

plugins/web_adapter/lib/src/adapter.dart

@@ -37,7 +37,8 @@ class BrowserHttpClientAdapter implements HttpClientAdapter {
     xhrs.add(xhr);
     xhr
       ..open(options.method, '${options.uri}')
-      ..responseType = 'arraybuffer';
+      ..responseType =
+          options.responseType == ResponseType.blobUrl ? 'blob' : 'arraybuffer';
 
     final withCredentialsOption = options.extra['withCredentials'];
     if (withCredentialsOption != null) {
@@ -66,18 +67,32 @@ class BrowserHttpClientAdapter implements HttpClientAdapter {
     final completer = Completer<ResponseBody>();
 
     xhr.onLoad.first.then((_) {
-      final ByteBuffer body = (xhr.response as JSArrayBuffer).toDart;
-      completer.complete(
-        ResponseBody.fromBytes(
-          body.asUint8List(),
-          xhr.status,
-          headers: xhr.getResponseHeaders(),
-          statusMessage: xhr.statusText,
-          isRedirect: xhr.status == 302 ||
-              xhr.status == 301 ||
-              options.uri.toString() != xhr.responseURL,
-        ),
-      );
+      if (options.responseType == ResponseType.blobUrl) {
+        completer.complete(
+          ResponseBody.fromString(
+            web.URL.createObjectURL(xhr.response as web.Blob),
+            xhr.status,
+            headers: xhr.getResponseHeaders(),
+            statusMessage: xhr.statusText,
+            isRedirect: xhr.status == 302 ||
+                xhr.status == 301 ||
+                options.uri.toString() != xhr.responseURL,
+          ),
+        );
+      } else {
+        final ByteBuffer body = (xhr.response as JSArrayBuffer).toDart;
+        completer.complete(
+          ResponseBody.fromBytes(
+            body.asUint8List(),
+            xhr.status,
+            headers: xhr.getResponseHeaders(),
+            statusMessage: xhr.statusText,
+            isRedirect: xhr.status == 302 ||
+                xhr.status == 301 ||
+                options.uri.toString() != xhr.responseURL,
+          ),
+        );
+      }
     });
 
     Timer? connectTimeoutTimer;

plugins/web_adapter/lib/src/dio_impl.dart

 dio.download( 
 dio.download( 
@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:dio/dio.dart';
 
 import 'adapter.dart';
@@ -25,9 +27,17 @@ class DioForBrowser with DioMixin implements Dio {
     String lengthHeader = Headers.contentLengthHeader,
     Object? data,
     Options? options,
-  }) {
-    throw UnsupportedError(
-      'The download method is not available in the Web environment.',
+  }) async {
+    return fetch(
+      RequestOptions(
+        baseUrl: urlPath,
+        data: data,
+        method: options?.method ?? 'GET',
+        responseType: ResponseType.blobUrl,
+        queryParameters: queryParameters,
+        cancelToken: cancelToken,
+        onReceiveProgress: onReceiveProgress,
+      ),
     );
   }
 }

plugins/web_adapter/test/browser_test.dart

@@ -18,4 +18,18 @@ void main() {
     browserAdapter.fetch(opts, testStream, cancelFuture);
     expect(browserAdapter.xhrs.every((e) => e.withCredentials == true), isTrue);
   });
+
+  test('ResponseType in blobUrl', () async {
+    final browserAdapter = BrowserHttpClientAdapter(withCredentials: true);
+    final opts = RequestOptions(responseType : ResponseType.blobUrl);
+    final testStream = Stream<Uint8List>.periodic(
+      const Duration(seconds: 1),
+          (x) => Uint8List(x),
+    );
+    final cancelFuture = opts.cancelToken?.whenCancel;
+
+    browserAdapter.fetch(opts, testStream, cancelFuture);
+    expect(browserAdapter.xhrs.every((e) => e.withCredentials == true), isTrue);
+    expect(opts.responseType, ResponseType.blobUrl);
+  });
 }