How to prevent WKWebView to repeatedly ask for permission to access location?

Turns out it’s quite hard, but possible to do. You have to inject JavaScript code which intercepts requests to navigator.geolocation and transfer them to your app, then get the location with CLLocationManager, then inject location back to the JavaScript.

Here is the brief scheme:

1. Add WKUserScript to your WKWebView configuration which overrides methods of navigator.geolocation. Injected JavaScript should look like this:

   navigator.geolocation.getCurrentPosition = function(success, error, options) { ... };
   navigator.geolocation.watchPosition = function(success, error, options) { ... };
   navigator.geolocation.clearWatch = function(id) { ... };
   

2. With WKUserContentController.add(_:name:) add script message handler to your WKWebView. Injected JavaScript should call your handler, like this:

   window.webkit.messageHandlers.locationHandler.postMessage('getCurrentPosition');
   

3. When a web page will request a location, this method will fire userContentController(_:didReceive:) so your app would know web page is requesting location. Find your location with the help of CLLocationManager as usual.

4. Now it’s time to inject the location back to the requesting JavaScript with webView.evaluateJavaScript("didUpdateLocation({coords: {latitude:55.0, longitude:0.0}, timestamp: 1494481126215.0})").
   Of course your injected JavaScript should have didUpdateLocation function ready to launch saved success handler.

Quite a long algorithm, but it works!