Provide mechanism to inspect an apps network traffic

[jonek]

It would be nice if the CLI would provide a way to inspect an app's network traffic.
That is any calls of the app to:

• fetch()
• XMLHttpRequest()

That traffic would be transmitted from a running app to the CLI using the existing web-socket mechanism already used to transfer the logging messages.

Having separate XHR and Request channels would be nice. This would be similar to the channels of the same name available in the Chrome dev tools.

There could be two types of output of the network traffic on the CLI side (all three toggles could work independently):

1. simple one-line meta data on stdout

• toggle --enable-request-log and --disable-XHR-log
• example output GET 200 http://foo.bar.net/some/path?queryparam=value 120ms

2. raw network traffic in form of one JSON object per request

• toggle --enable-raw-network
• example output

{
        "time": 34.19247499189805,
        "request": {
          "method": "GET",
          "url": "http://foo.bar.net/some/path?queryparam=value",
          "httpVersion": "HTTP/1.1",
          "headers": [
            {
              "name": "Host",
              "value": "foo.bar.net"
            },
            {
              "name": "Connection",
              "value": "keep-alive"
            },
            {
              "name": "Pragma",
              "value": "no-cache"
            },
            {
              "name": "Cache-Control",
              "value": "no-cache"
            },
            {
              "name": "Upgrade-Insecure-Requests",
              "value": "1"
            },
            {
              "name": "User-Agent",
              "value": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.67 Safari/537.36"
            },
            {
              "name": "Accept",
              "value": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8"
            },
            {
              "name": "Referer",
              "value": "http://baz.net/"
            },
            {
              "name": "Accept-Encoding",
              "value": "gzip, deflate, br"
            },
            {
              "name": "Accept-Language",
              "value": "en-US,en;q=0.9,de;q=0.8"
            },
            {
              "name": "Cookie",
              "value": "SOME_ID=asdfasdfasdf; SOME_OTHER_KEY=1234;"
            }
          ],
          "queryString": [
            {
              "name": "queryparam",
              "value": "value"
            }
          ],
          "cookies": [
            {
              "name": "SOME_ID",
              "value": "asdfasdfasdf",
              "expires": null,
              "httpOnly": false,
              "secure": false
            },
            {
              "name": "SOME_OTHER_KEY",
              "value": "1234",
              "expires": null,
              "httpOnly": false,
              "secure": false
            }
          ],
          "headersSize": 1661,
          "bodySize": 0
        },
        "response": {
          "status": 303,
          "statusText": "See Other",
          "httpVersion": "HTTP/1.1",
          "headers": [
            {
              "name": "Server",
              "value": "nginx/1.10.3 (Ubuntu)"
            },
            {
              "name": "Date",
              "value": "Fri, 02 Nov 2018 16:54:03 GMT"
            },
            {
              "name": "Content-Length",
              "value": "0"
            },
            {
              "name": "Connection",
              "value": "keep-alive"
            },
            {
              "name": "Location",
              "value": "http://some.other.url"
            },
            {
              "name": "Strict-Transport-Security",
              "value": "max-age=15768000"
            }
          ],
          "cookies": [],
          "content": {
            "size": 0,
            "mimeType": "x-unknown",
            "compression": 0
          },
          "redirectURL": "http://some.other.url",
          "headersSize": 492,
          "bodySize": 0,
          "_transferSize": 492
        }
}

[jonek]

The JSON example was a request I exported from my Chrome dev tools' "network" tab via "right click" -> "Copy" -> "Copy all as HAR".