Improve type safety for dynamic stylesheet rules

[chetanr-25]

This PR improves type safety when accessing dynamic stylesheet rules
by ensuring a consistent CSSRuleList return type.

No functional behavior is changed.

[vs-code-engineering]

📬 CODENOTIFY

The following users are being notified based on files changed in this PR:

@bpasero

Matched files:

• src/vs/base/browser/domStylesheets.ts

[chetanr-25]

This is my first contribution — happy to make any requested changes. Thank you for reviewing!

[mjbvz]

Thanks!

[chetanr-25]

@microsoft-github-policy-service agree

[chetanr-25]

agree

…

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[mjbvz]

I'd prefer this just return undefined in these cases

And actually do we even need this helper function now? The 2 callers can be converted to style.sheet?.cssRules instead

[chetanr-25]

Agreed — removed the helper and updated both call sites to use
style.sheet?.cssRules directly. Thanks!

[mjbvz]

Hey looks like this change didn't make it in yet, right?

[chetanr-25]

Yep, it’s approved but not merged yet. Let me know if I should do anything else or if it’s waiting on a maintainer.

[mjbvz]

Sorry what I meant is that I don't think we need getDynamicStyleSheetRules at all now. I pushed a change that just inlines which simplifies the code quite a bit. Let me know if you don't think that will work

[chetanr-25]

The inlined changes look great and definitely simplify the code. I'm happy with this approach. Thanks for the help!

[chetanr-25]

Agreed — removed the helper and updated both call sites to use style.sheet?.cssRules directly. Thanks!

…

On Wed, Jan 21, 2026 at 6:04 AM Matt Bierner ***@***.***> wrote: ***@***.**** commented on this pull request. ------------------------------ In src/vs/base/browser/domStylesheets.ts <#288651 (comment)>: > } - if (style?.sheet?.cssRules) { - return style.sheet.cssRules; // FF - } - return []; + + const emptyRules: CSSRule[] = []; + + return { I'd prefer this just return undefined in these cases And actually do we even need this helper function now? The 2 callers can be converted to style.sheet?.cssRules instead — Reply to this email directly, view it on GitHub <#288651 (review)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/BWWNJYGEIH3GRIB4TED7S3L4H3CRLAVCNFSM6AAAAACSA7YY4GVHI2DSMVQWIX3LMV43YUDVNRWFEZLROVSXG5CSMV3GSZLXHMZTMOBUHA2TIOBXHA> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[chetanr-25]

Hi @mjbvz, I've updated the PR to remove the helper function and used optional chaining as suggested. I also just merged the latest main branch to keep it up to date. Ready for the tests to run and a final review whenever you have a moment! Thanks!

[mjbvz]

@chetanr-25 Please hold off on updating the branch. It means I have to re-approve the PR each time