Headers emulation and setHeaders method to update headers #92

FZambia · 2025-01-23T18:51:43Z

Support Headers Emulation introduced in Centrifugo v6.

This PR changing headers from Map<String, dynamic> to Map<String, String> in Client config. This is a breaking change, but I believe it must not cause huge troubles beyond a simple refactoring, I never seen someone using multiple values for the same header. If we find such a case - can bring dynamic back.

Also some refactoring to get rid of dart.html

PlugFox · 2025-01-23T19:12:54Z

example/console/example.dart

+          // If you want to use Headers in web environment – make sure your headers use
+          // string values, centrifuge-dart will then automatically attach them to connect
+          // frame (using Headers Emulation feature).
          headers: <String, dynamic>{'X-Example-Header': 'example'},


<String, Object?>{} better than <String, dynamic>{}

dynamic means "This can be everything, and you can call everything; do not check type"
Object? means "This is can be everything, but you should check the type before do anything"

Thats a bad practice to use dynamic anywhere, because you just omit any type checks, e.g.:

void main() { dynamic x = "string"; x.toDouble(); // Exception during runtume }

Let's try to move away from it and try using Map<String, String>, did in latest commit

PlugFox · 2025-01-23T19:13:37Z

example/web_app/web/main.dart

    url,
-    ClientConfig(),
+    ClientConfig(
+      headers: <String, dynamic>{'Authorization': 'example'},


<String, Object?>{'Authorization': 'example'},

Not actual with Map<String, String> anymore

PlugFox · 2025-01-23T19:28:51Z

lib/src/client.dart

+import 'web_in.dart' if (dart.library.js_interop) 'web_in.dart' as web;
+import 'web_out.dart' if (dart.library.io) 'web_out.dart' as nonweb;
+
+bool isWeb() {
+  try {
+    return web.isWebContext();
+  } catch (_) {
+    return nonweb.isWebContext();
+  }
+}


Правильный способ, если тебе просто нужна константа для понимания веб это или нет:

const bool kIsWeb = bool.fromEnvironment('dart.library.js_util');

суть способа в проверке доступность библиотеки js_util на этапе компиляции, тк она существует только для JS и WASM
этот способ использует Flutter SDK

также можно

const bool kIsWeb = identical(0, .0);

это точно будет работать в вебе при транспиляции Dart в JS, но есть сомнения на счет WASM
суть хинта в том, что для JS 0.0 и 0 это ссылка на один и тот же литерал num. а для всех остальных платформ это разные инстансы int и double
этот способ раньше до WASM использовал Flutter SDK

а если хочешь сделать через импорты, надо записать вместо:

import 'web_in.dart' if (dart.library.js_interop) 'web_in.dart' as web; import 'web_out.dart' if (dart.library.io) 'web_out.dart' as nonweb;

так (тоесть именно в ЕДИНОМ импорте указывай "if"):

import 'vm.dart' // ignore: uri_does_not_exist if (dart.library.js_interop) 'js.dart';

и создать два файла vm.dart и js.dart
в каждом из которых методы и геттеры с одинаковыми сигнатурами, например чото типа того:

bool get isWeb => true; Map<String, Object?> getPlatformMetadata() => <String, Object?>{ 'agent': window.navigator.userAgent };

If you want separate files for each platform you should do this way:

$ mkdir platform/ $ echo "const bool kIsWeb = true;" > platform/js.dart $ echo "const bool kIsWeb = false;" > platform/vm.dart

and optionally create barrel file platform.dart:

export 'platform/vm.dart' // ignore: uri_does_not_exist if (dart.library.js_interop) 'platform/js.dart'; /* import 'platform/vm.dart' // ignore: uri_does_not_exist if (dart.library.js_interop) 'platform/js.dart'; void main() { print(kIsWeb ? 'Web' : 'Not Web'); } */

Thanks! Changed to use a single import with if

PlugFox · 2025-01-23T19:30:01Z

lib/src/client.dart


+  /// Set allows updating connection headers.
+  ///
+  void setHeaders(Map<String, dynamic> headers);


Map<String, /* String | List<String> */ Object?> headers
or
Map<String, String> headers
or
Map<String, List<String>> headers

PlugFox · 2025-01-23T19:36:03Z

lib/src/client.dart

+  @override
+  void setHeaders(Map<String, dynamic> headers) {
+    _headers = headers;
+  }


A bit safer option to make copy of headers, because user can pass mutable HashMap and mutate it over time.

@override void setHeaders(Map<String, Object?> headers) => _headers = Map<String, Object?>.of(headers);

or

@override void setHeaders(Map<String, Object?> headers) => _headers = <String, Object?>{ for (final MapEntry(:String key, :Object? value) in headers.entries) if (value is String) key: value else if (value is Iterable) key: value.whereType<String>().join(', '), };

PlugFox · 2025-01-23T19:39:13Z

lib/src/client.dart

+    if (isWeb()) {
+      // Use headers emulation in web context.
+      final Map<String, String> emulatedHeaders = Map.fromEntries(
+        _headers.entries
+            .where((entry) => entry.value is String)
+            .map((entry) => MapEntry(entry.key, entry.value as String)),
+      );
+      request.headers.addAll(emulatedHeaders);
+    }


if (kIsWeb) { // It would be a dead code and tree shaked at Dart VM (dart:io) platforms // Use headers emulation in web context. request.headers.addAll(<String, String>{ for (final MapEntry(:String key, :Object? value) in headers.entries) if (value is String) key: value else if (value case Iterable iterable) key: iterable.whereType<String>().join(', ') /* or: key: iterable.firstOrNull?.toString() ?? '', or: for (final e in iterable.whereType<String>()) key: e, */ }); }

That work this way:

import 'dart:convert'; void main() { final headers = { '1': 'a', '2': ['b', 'c', 'd'], '3': 'e', }; print(const JsonEncoder.withIndent(' ').convert( <String, String>{ for (final MapEntry(:String key, :Object? value) in headers.entries) if (value is String) key: value else if (value case Iterable iterable) key: iterable.whereType<String>().join(', ') /* or: key: iterable.firstOrNull?.toString() ?? '', or: for (final e in iterable.whereType<String>()) key: e, */ } )); /* { "1": "a", "2": "b, c, d", "3": "e" } */ }

Thx, not actual anymore

PlugFox · 2025-01-23T19:45:11Z

lib/src/web_in.dart

+// This file is only used in web environments
+bool isWebContext() => true; // Always returns true in web contexts


Take a look at suggestion before.

If you want separate files for each platform you should do this way:

$ mkdir platform/ $ echo "const bool kIsWeb = true;" > platform/js.dart $ echo "const bool kIsWeb = false;" > platform/vm.dart

and optionally create barrel file platform.dart:

export 'platform/vm.dart' // ignore: uri_does_not_exist if (dart.library.js_interop) 'platform/js.dart'; /* import 'platform/vm.dart' // ignore: uri_does_not_exist if (dart.library.js_interop) 'platform/js.dart'; void main() { print(kIsWeb ? 'Web' : 'Not Web'); } */

Done I suppose

PlugFox · 2025-01-23T19:46:12Z

lib/src/client.dart

  ClientConfig _config;
  ClientConfig get config => _config;

+  Map<String, dynamic> _headers = {};


You no need default value here, if set it before constructors body:

ClientImpl(this._url, this._config, this._transportBuilder) : _token = _config.token, _data = _config.data, _headers = _config.headers; Map<String, Object?> _headers;

or you can make it late and use constructors body:

ClientImpl(this._url, this._config, this._transportBuilder) { _token = _config.token; _data = _config.data; _headers = _config.headers; } late Map<String, Object?> _headers;

PlugFox · 2025-01-23T19:47:29Z

lib/src/client.dart

  ClientImpl(this._url, this._config, this._transportBuilder) {
    _token = _config.token;
    _data = _config.data;
+    _headers = _config.headers;
  }


ClientImpl(this._url, this._config, this._transportBuilder) : _token = _config.token, _data = _config.data, _headers = _config.headers;

You can set it before constructor's body.
And optionally make a copy of hash map.

* update web_socket_channel, min SDK 3.3 * Headers emulation and setHeaders method to update headers (#92)

FZambia added 2 commits January 23, 2025 20:50

headers emulation

d40fd90

migrate to web package

4bd3a36

FZambia temporarily deployed to test_ci January 23, 2025 19:04 — with GitHub Actions Inactive

PlugFox suggested changes Jan 23, 2025

View reviewed changes

various review fixes

465efba

FZambia temporarily deployed to test_ci January 24, 2025 17:53 — with GitHub Actions Inactive

FZambia marked this pull request as ready for review January 24, 2025 18:02

FZambia merged commit 4c23682 into up_web_socket_channel Jan 25, 2025
4 checks passed

FZambia deleted the headers_emulation branch January 25, 2025 06:39

FZambia added a commit that referenced this pull request Jan 25, 2025

Update web_socket_channel to the latest, min SDK 3.3 (#91)

92fdf95

* update web_socket_channel, min SDK 3.3 * Headers emulation and setHeaders method to update headers (#92)

FZambia mentioned this pull request Jan 25, 2025

v0.15.0 development #93

Merged

		// This file is only used in web environments
		bool isWebContext() => true; // Always returns true in web contexts No newline at end of file

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Headers emulation and setHeaders method to update headers #92

Headers emulation and setHeaders method to update headers #92

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FZambia commented Jan 23, 2025 •

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