WKWebView.backForwardList.currentItem is incorrect after canceled back/forward navigation

• Component: Page Loading
• Status: RESOLVED WORKSFORME

[Danyao Wang]

Created attachment 344701 [details]
Minimal example to reproduce the bug

For back/forward navigation, WebKit's URL and history state are updated before the |webView:decidePolicyForNavigationAction| callback. If the embedder returns WKNavigationActionPolicyCancel, only the URL change is undone, but not the WKWebView.backForwardList.currentItem change.

Steps to reproduce:
1. Navigate to a URL in WKWebView, e.g. https://wikipedia.org
2. Navigate to a second URL: e.g. https://apple.com
3. Go back
4. In |webView:decidePolicyForNavigationAction|, return WKNavigationActionPolicyCancel
5. Observe WKWebView.URL and WKWebView.backForwardList.currentItem.URL in URL KVO

Expected result: both WKWebView.URL and WKWebView.backForwardList.currentItem.URL are https://apple.com
Observed result: WKWebView.URL is https://apple.com. WKWebView.backForwardList.currentItem.URL is https://wikipedia.org.

The attached WKWebView project runs through the above states and logs the URLs to debug log.

The history state is corrected after starting a new navigation. So this may be a discrepancy between the WebProcess and UIProcess.

[Ali Juma]

In reply to Danyao Wang from comment #0)
> So this may be a discrepancy between the WebProcess and UIProcess.

FrameLoader::continueLoadAfterNavigationPolicy has logic (in the !canContinue case) to reset back/forward state. Perhaps something is going wrong with sending that change to the UIProcess.

[Radar WebKit Bug Importer]

<rdar://problem/42032341>

[Brent Fulgham]

This bug doesn't seem actionable.