Don't crash when theme.keyframes is explicitly set to null

[koreahghg]

Summary

Setting theme.keyframes (or theme.extend.keyframes) to null in a JS config crashes the entire build.

keyframesToRules in packages/tailwindcss/src/compat/apply-keyframes-to-theme.ts checks 'keyframes' in resolvedConfig.theme before calling Object.entries(resolvedConfig.theme.keyframes). But resolveConfig (see packages/tailwindcss/src/compat/config/resolve-config.ts) resolves every theme value with value ?? null, so a theme key explicitly set to null — the documented way to clear a theme key, e.g. theme.extend.colors: null — still exists on the object via in, just with a null value. That means theme: { keyframes: null } reaches Object.entries(null), which throws TypeError: Cannot convert undefined or null to object and crashes the whole build.

Every sibling module that reads from the resolved theme this way (container.ts, screens-config.ts, etc.) already guards against this with a falsy/|| {} check — this file was the one outlier still using in.

Fix

Swap the 'keyframes' in resolvedConfig.theme check for a truthy check on resolvedConfig.theme.keyframes itself, matching the pattern used elsewhere in compat/.

Test plan

• Added a regression test to apply-keyframes-to-theme.test.ts: theme: { keyframes: null } no longer throws and correctly results in no keyframes.
• Verified the new test fails with the exact reported crash on the code prior to this fix, and passes after.
• pnpm vitest run — all 5008 tests in the tailwindcss package pass (5007 existing + 1 new), no regressions.
• tsc --noEmit shows no new type errors introduced by this change (pre-existing, unrelated errors exist elsewhere in the monorepo from packages that require a built @tailwindcss/oxide native module).

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

_{Reviews (2): Last reviewed commit: "Correct changelog wording and add extend..." | Re-trigger Greptile}

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 3ed844e3-a118-4b7b-aee9-419afa7667ed

📥 Commits

Reviewing files that changed from the base of the PR and between afd20c6 and 9c3e06e.

📒 Files selected for processing (2)

• CHANGELOG.md
• packages/tailwindcss/src/compat/apply-keyframes-to-theme.test.ts

🚧 Files skipped from review as they are similar to previous changes (1)

• CHANGELOG.md

Included review availability: Your plan provides up to 10 included reviews per hour; 8 remain after this review.

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Walkthrough

The keyframe conversion guard now processes theme.keyframes only when it is truthy. Regression tests cover null theme.keyframes and null theme.extend.keyframes values. The changelog documents the fix for null theme.keyframes configuration.

Merge Risk: ⚪ Minimal · up to 9c3e0

This localized fix prevents builds from crashing when theme.keyframes is explicitly null, with regression coverage and no actionable merge-blocking risk remaining after normal checks and review.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main fix for the crash caused by an explicit null value in theme.keyframes.
Description check	✅ Passed	The description accurately explains the crash, the fix, the regression tests, and the validation results.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[coderabbitai]

Actionable comments posted: 1

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: e0619246-a2f1-47bf-8ae7-86a5a15c392e

📥 Commits

Reviewing files that changed from the base of the PR and between 90f8ff4 and afd20c6.

📒 Files selected for processing (3)

• CHANGELOG.md
• packages/tailwindcss/src/compat/apply-keyframes-to-theme.test.ts
• packages/tailwindcss/src/compat/apply-keyframes-to-theme.ts

Included review availability: Your plan provides up to 10 included reviews per hour; 9 remain after this review.

[koreahghg]

Thanks for the review!

Re: the suggestion to also cover `theme.extend.keyframes: null` — good catch that it wasn't covered, but worth noting that path never actually hit the crash: `deepMerge` skips `null`/`undefined` sources entirely (see `compat/config/deep-merge.ts`), so the resolved value there is always `{}`, not `null`. I've pushed a follow-up commit that:

• corrects the changelog line, which incorrectly implied the `extend` path was also crashing
• adds a dedicated regression test for `theme.extend.keyframes: null` anyway, so a future change to `deepMerge`/`resolveConfig` can't silently reintroduce a crash there too

Full suite still green (5009/5010, 1 pre-existing skip).