Add "base", "final" and "interface" modifiers (#920)

Author: brianquinlan

.github/workflows/dart.yml

@@ -1,3 +1,8 @@
+## 1.0.0
+
+* Requires Dart 3.0 or later.
+* Add `base`, `final`, and `interface` modifiers to some classes.
+
 ## 0.13.6
 
 * `BrowserClient` throws an exception if `send` is called after `close`.

pkgs/http/CHANGELOG.md

@@ -14,7 +14,7 @@ import 'http.dart';
 /// NOTE: [RetryClient] makes a copy of the request data in order to support
 /// resending it. This can cause a lot of memory usage when sending a large
 /// [StreamedRequest].
-class RetryClient extends BaseClient {
+final class RetryClient extends BaseClient {
   /// The wrapped client.
   final Client _inner;
 

pkgs/http/lib/retry.dart

@@ -17,7 +17,7 @@ import 'streamed_response.dart';
 ///
 /// This is a mixin-style class; subclasses only need to implement [send] and
 /// maybe [close], and then they get various convenience methods for free.
-abstract class BaseClient implements Client {
+abstract mixin class BaseClient implements Client {
   @override
   Future<Response> head(Uri url, {Map<String, String>? headers}) =>
       _sendUnstreamed('HEAD', url, headers);

pkgs/http/lib/src/base_client.dart

@@ -7,7 +7,7 @@ import 'dart:convert';
 import 'dart:typed_data';
 
 /// A stream of chunks of bytes representing a single piece of data.
-class ByteStream extends StreamView<List<int>> {
+final class ByteStream extends StreamView<List<int>> {
   const ByteStream(super.stream);
 
   /// Returns a single-subscription byte stream that will emit the given bytes

pkgs/http/lib/src/byte_stream.dart

@@ -29,7 +29,7 @@ import 'streamed_response.dart';
 /// extend [BaseClient] rather than [Client]. In most cases, you can wrap
 /// another instance of [Client] and add functionality on top of that. This
 /// allows all classes implementing [Client] to be mutually composable.
-abstract class Client {
+abstract interface class Client {
   /// Creates a new platform appropriate client.
   ///
   /// Creates an `IOClient` if `dart:io` is available and a `BrowserClient` if

pkgs/http/lib/src/client.dart

@@ -4,7 +4,7 @@ description: A composable, multi-platform, Future-based API for HTTP requests.
 repository: https://github.com/dart-lang/http/tree/master/pkgs/http
 
 environment:
-  sdk: '>=2.19.0 <3.0.0'
+  sdk: '>=3.0.0-417.4.beta <4.0.0'
 
 dependencies:
   async: ^2.5.0