Choosing between package:html, dart:html, dart:io

I realized that currently there are at least three "official" Dart libraries that allow me to perform a HTTP request. What is more, three of those libraries (dart:io (class HttpClient), package:http and dart:html) have each a different, incompatible API.

As of today, package:html does not offer this functionality, but on its GitHub page I found it aims for 100% API compatibility with dart:html, so these methods will be added there eventually.

Which package provides the most future proof and platform independent API to issue a HTTP request in Dart?

Is it package:http?

import 'package:http/http.dart' as http;

var url = "http://example.com";
http.get(url)
    .then((response) {
  print("Response status: ${response.statusCode}");
  print("Response body: ${response.body}");
});

Is it dart:html/package:html?

import 'dart:html';

HttpRequest.request('/example.json')
  .then((response) {
      print("Response status: ${response.status}");
      print("Response body: ${response.response}");
});

Or dart:io?

import 'dart:io';

var client = new HttpClient();
client.getUrl(Uri.parse("http://www.example.com/"))
    .then((HttpClientRequest request) {
      // Optionally set up headers...
      // Optionally write to the request object...
      // Then call close.
      ...
      return request.close();
    })
    .then((HttpClientResponse response) {
      print("Response status: ${response.statusCode}");
      print("Response body:");
      response.transform(UTF8.decoder).listen((contents) {
        print(contents);
      });
    });

Let's say I want to cover Android too. That adds package:sky in the mix as well (https://github.com/domokit/sky_sdk/). I admit that this is not "official" Google library.

import 'package:sky/framework/net/fetch.dart';

Response response = await fetch('http://example.com');
print(response.bodyAsString());

What is (going to be) a regular product is https://www.youtube.com/watch?v=t8xdEO8LyL8. I wonder what their HTTP Request story is going to be. Something tells me it will be yet another different beast from all we have seen so far.

The html package is a HTML parser which allows to work with HTML server side. I wouldn't expect it to get some HttpRequest capabilities.

The http package aims to provide a unified API for client and server Dart code. The API in dart:html is only a wrapper over the API the browser provides. The HttpRequest API in dart:io was built without browser restrictions and thus deviates from dart:html. package:http provides an unified API which delegates to dart:html when run in the browser and to dart:io when run on the server.

I think package:http is future proof and cross-platform and should be a good fit for your requirements.