Create a custom persistent WKWebsiteDataStore with specified cookieStorageFile, set a persistent cookie through Cookie API. Then Create another custom persistent WKWebsiteDataStore with same cookieStorageFile, and call getAllCookies from this store, we would get nothing.
Similarly, two uses of the defaultDataStore will not persist cookie changes across process launches. Similarly, if an app uses a WKWebView and the WKWebView stores some data -- cookies, databases, whatever -- then when the app relaunches I think its defaultDataStore will not be able to get or remove its data, until you first load a webpage.
<rdar://problem/40343792>
<rdar://problem/40343788>
Currently all WKHTTPCookieStores fetch cookies via network process, and on Cocoa platform network process is a singleton, so we will be able to get cookies from different stores with the same cookie file path.