Why webRequest.onBeforeSendHeaders doesn't provide query string while browser.webNavigation.onBeforeNavigate does? - firefox-addon-webextensions

Question

I am trying to implement a web extension which removes redirect intermediate from links. For example, when you click any link to foreign site from vk.com (a social network), you'll be navigated to https://vk.com/away.php?to=URL_GOES_HERE.
When you listen to onBeforeNavigate events like that:
browser.webNavigation.onBeforeNavigate.addListener(
(details) => {
console.log('before navigate', details);
}, {
url: [
{hostContains: "vk.com"}
]
}
);
you'll get full URL: before navigate Object { url: "https://vk.com/away.php?to=URL_GOES_HERE", timeStamp: 1488807415002, frameId: 0, parentFrameId: -1, tabId: 2 }
But you have no option to replace that navigation action with another URL. You have that ability only for webRequest API:
browser.webRequest.onBeforeSendHeaders.addListener(
(details) => {
console.log('before web request', details)
},
{urls: [
'*://vk.com/away.php'
]},
['blocking', 'requestHeaders']
);
but URL there doesn't contain query parameters: before web request Object { requestId: "1", url: "http://vk.com/away.php", originUrl: "https://vk.com/feed", method: "GET", type: "main_frame", timeStamp: 1488807415092, frameId: 0, parentFrameId: -1, tabId: 2, requestHeaders: Array[6] }
Why is it working so? Is it a bug or what?

Answer 1

Documentation doesn't clealy states that query string is implicitly treated as part of URL path. So asterisk at the end is required. The following code works and removes intermediate request:
browser.webRequest.onBeforeRequest.addListener(
(details) => {
let url = new URL(details.url), param;
switch (url.hostname) {
case 'vk.com':
param = 'to';
break;
default:
param = 'url';
}
let direct = new URLSearchParams(url.search).get(param);
console.log('DIRECT: ' + direct + ' (' + url + ')');
return {redirectUrl: direct}
},
{urls: [
'*://vk.com/away.php?*',
'*://www.google.ru/url?*',
'*://www.google.com/url?*',
]},
['blocking']
);