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[scovich]

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I noticed today that the "hide whitespace" option is not working any more??

Note how the function signatures are completely unchanged, other than indentation (verified in my editor).

Showing the diff with git diff -b gives a very different result, so I'm not so sure that's a helpful comparison:

Details

The pull request in question is https://github.com/apache/arrow-rs/pull/9144/changes?w=1 (note the w=1).
The file in question is a "large diff.. not rendered by default", not sure if that's related?

[isatyamshivam]

The “Hide whitespace changes” option still works, but it may look broken for large diffs or collapsed files. GitHub doesn’t always apply this setting when the file is too big or not fully loaded. Try expanding the file or adding ?w=1 to the PR URL to ignore whitespace changes.

[Youjjwal]

The “Hide whitespace changes” feature is not actually broken, but it has limitations on GitHub’s diff viewer.

In this case, the file is marked as “large diff – not rendered by default”, and for such files GitHub does not reliably apply whitespace filtering (even when w=1 is present). When the diff is partially rendered or collapsed, indentation-only changes can still appear as full diffs.

A few things to note:

GitHub only applies whitespace hiding correctly when the file is fully expanded and rendered

Large diffs may bypass whitespace filtering due to performance constraints

git diff -b locally is more reliable because it operates on the full file, not a partial render

So the behavior you’re seeing is a GitHub UI limitation, not a change in how whitespace filtering works. Expanding the entire file or reviewing the diff locally is the most accurate workaround.

[scovich]

@Youjjwal I suspected the large diff was related, but could you clarify what you mean by "fully expanded and rendered" ?

Expanding the entire file... is the most accurate workaround

Do you mean it only works for files that do render by default or are you referring to a workaround of some kind?

[Youjjwal]

Good question — let me clarify.

By “fully expanded and rendered” I mean files that GitHub actually loads and displays the complete diff for, not ones that stay in the “large diff — not rendered by default” state.

There are two different cases:

1. Files that render by default
   For normal-sized diffs, GitHub fully renders the file immediately. In these cases, Hide whitespace changes / ?w=1 works reliably.

2. Large diffs that are collapsed or partially loaded
   When a file is marked as “large diff — not rendered by default”, GitHub only shows a limited or truncated view unless you explicitly expand it. In this state, whitespace filtering is inconsistent or skipped, even if w=1 is present.

So the workaround I was referring to is:

• Manually expanding the entire file (when GitHub allows it), which can sometimes make whitespace hiding behave more correctly
• Or reviewing the change locally with git diff -b, which always operates on the full file and ignores whitespace reliably

In short:
It’s not that whitespace hiding is disabled globally — it just doesn’t consistently apply to large, non-fully-rendered diffs due to UI/performance constraints.

[scovich]

I've never understood why github UI doesn't just use git diff -b when users request to hide whitespace changes... it anyway reloads the whole page. But ok.

[Youjjwal]

so you got your answer ?

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