Browser extension: No hover tooltips on GitHub PRs after switching tabs

[KattMingMing]

• Visit adding Router.Name to create new Route gorilla/mux#457
• Then click on "Files" to go to the diff view
• Hover over Route on line 289 at the top
• Notice the token becomes highlighted, but the hover tooltip doesn't show up

[KattMingMing]

After refreshing the background page of the browser extension and refreshing the GitHub PR page I was able to get tooltips to show. There was no hover tooltip or any other indications that code intel was working until I did this – I also added and removed the extension.

[felixfbecker]

Interesting. Were there any errors in the console or background page console?

[chrismwendt]

I'm unable to repro (browser extension v19.4.8.1301) at https://github.com/sourcegraph/sourcegraph/pull/3227/files#diff-a98755ff0b47687b4ea8b2cc6294950eR209

[chrismwendt]

I found a repro. I added repro steps to the description + a GIF showing the bug.

[felixfbecker]

Thanks for the repro @chrismwendt! This only happens after switching tabs. The hover overlay mount, which is appended to the #js-repo-pjax-container, gets removed and not readded. I guess this is because GitHub swaps out the content of #js-repo-pjax-container, but will never remove/add #js-repo-pjax-container itself, so we don't add the mount again. I don't actually know why we don't just put the mount on document.body, I think this was a hacky attempt to make hover overlays disappear on page navigation, but I have since added proper handling for that. Using document.body fixes the issue.