added downloadProgress and uploadProgress

[Mehmetyaz]

I have reviewed the issues discussed previously #728 . There were quite a few changes, so I closed PR and reopened it. I also tackled this feature from scratch.

Now we can listen to events for both download and upload.

Optionally, we can also provide data such as speed / remaining time estimation by recording past events over a certain period of time. We also provide records so that the developer can do the calculations themselves.

Example added: pkgs/http/example/progress.dart

It tested in pkgs/http/test/io/streamed_request_test.dart

It was also tested on the browser side with a pkgs/mock_server and pkgs/http/test/html/progress_test.dart.

I'm not sure if I spent enough time on documentation. I want to update it according to demand.

http.post(
    Uri.parse('https://example.com'),
    downloadProgress: HttpProgress((event) {
        event.lengthComputable;
        event.total;
        event.transferred;
        event.progressRate;
        event.percent([fractionDigits])  
    }),
    
    uploadProgress: HttpProgress.withRecorder((event) {
       
        // additionally
        event.records; // List<(int, DateTime)>;
        event.averageSpeed;   event.lastSpeed;   event.estimatedRemaining;
    }),
    ....
)

@kevmoo @brianquinlan @natebosch

[Mehmetyaz]

I noticed the analyzer info. I will fix it. Also, the pkgs/http/test/html/progress_test.dart test will not be successful. That file should be deleted after the Dart team tests it.

[kevmoo]

Not sure if I like the callback model here...but not sure if there is a better way to do it.

@natebosch @devoncarew – thoughts?

We certainly need to be careful about breaking changes...

[Mehmetyaz]

Not sure if I like the callback model here...but not sure if there is a better way to do it.

@natebosch @devoncarew – thoughts?

We certainly need to be careful about breaking changes...

Actually, I also feel like there is something not quite right (I think that's why I thought of a different model when I started). I can update if there is any suggestion. The basic logic works, after all, and changing the callback model can be done quickly.

[AlexV525]

Same as #579