Page loading indicator freezes indefinitely when navigating to a missing #anchor after first page load

• Component: Page Loading
• Status: NEW ---

[Jeff Standen]

Overview:
In Safari (Mac) 10.1 and 11.0 (but not 9.1) the page loading indicator freezes indefinitely when navigating to an #anchor after a page has already loaded.

Steps to reproduce:
1. In an affected version, navigate to a page like https://bugs.webkit.org/
2. Let the page finish loading.
3. In the location bar (Cmd+L) append "#missing-anchor" to the existing URL and press <ENTER>.

Actual result:
The page loading indicator progresses to about 10% and freezes there indefinitely.

Expected result:
Since the #anchor doesn't exist, we expect nothing to happen. The scrollbar would remain in the same position, and the page loading indicator would finish almost instantly (if it displayed at all).

This issue occurs on Safari 10.1 and 11.0 on Mac Sierra + High Sierra. I tested on several different machines, including BrowserStack. I tested using many different websites. The issue existed everywhere on the affected versions.

This issue doesn't occur on Safari 9.1 (or any other major browsers).

The issue doesn't occur if you navigate directly to a URL like https://bugs.webkit.org/#missing-anchor -- it only occurs when you link to a non-existing #anchor on a previously loaded page.

[Radar WebKit Bug Importer]

<rdar://problem/35657377>