Pull request diff page crashes and is super slow, dropdowns not opening #2273

Can you try to disableshow-whitespace? It could help with the slowdown.

I’m not sure what the problem with the dropdowns is. Can you right click on them and see what element is covering them (if any)?

I'm not sure what changed but this no longer seems to be an issue for me. I'll reopen and try some more things if it comes up again.

Found this issue when googling for "github diff slow" because github diff/PR reviewing have been so slow that I can't use it for things larger that 100 lines or so. Now I had this PR of 1500 changed files and really needed to create a review comment but couldn't, so after finding this issue I disabled the Refined Github extension and I can now use GitHub (web) again! 🍾

@anderssonjohan could you see which feature caused the slowdown? You can disable them in the options.

@fregante Silly me, didn't know that there was feature toggles. I re-activated the plugin now but couldn't get the error immediately. Will try the feature toggles if the problem arises again and post here. Thanks!

There are too many options to try but it is also super slow if there are hundreds of files and it hangs when I am typing to add a comment. Have to disable it for now 😢

I have been struggling with the PR screen as well. The page would lock up while it attempted to render, and after scrolling down a bit the diffs would be completely blank. Eventually the tab would hang and Chrome would ask me to kill it. Disabling the show-whitespace option did the trick though. With that option disabled everything seems to be working great. Thanks for the suggestion @fregante!

Can we please reopen this? Reviewing PRs with Refined Github enabled becomes a painful experience even on a monstrous workstation, let alone a laptop. I'll see if I can figure out which option specifically causes the slow down, but the issue has made me use a VS Code extension for moving the PR review workflow out of GitHub altogether as I didn't want to ditch Refined Github 😞

That's probably show-whitespace again. But you'll have to provide us with a PR as example so that we can confirm this behavior.

Doesn't seem to be it alone.

I've solved it on my end and found 3 culprits (sorted starting with the biggest bottleneck) I've now disabled:

1. show-whitespace
2. highlight-deleted-and-added-files-in-diffs
3. linkify-code

Tested with a PR containing 100+ file changes on a 3900x, the entire PR normally takes < 1 second to render while scrolling. Enabling either of these 3 options introduced a notorious lag of 10+ seconds any time significant scroll occurs. show-whitespace however was indeed the biggest show stopper, introducing a lag of at least 30 seconds.

show-whitespace however was indeed the biggest show stopper, introducing a lag of at least 30 seconds.

We do not have any concept of vdom as such that we can use to render only the things in viewport as VSCode does natively. Which is why these features end up being a bit heavy on very-very-long PRs.

For example, the laptop I'm on right now would crash if I tried to load all 100+ diffs of a PR even without having this extension installed.

Tested with a PR containing 100+ file changes on a 3900x, the entire PR normally takes < 1 second to render while scrolling.

I'm not sure if GitHub would let you render 100+ diffs on the same page in < 1 second, but that's another issue.

Also, can't help you if you can't provide an example of a public PR.

I opened https://github.com/sindresorhus/refined-github/issues/3567 but real-life links are needed to see what's going on effectively.

show-whitespace doesn't do anything but just observe all elements via IntersectionObserver, which in my tests on large PRs had no effect. Its behavior was specifically improved for large PRs in #2737