Fix drop-shadow ignoring its opacity modifier when no size is specified

[koreahghg]

Summary

The bare drop-shadow utility (no size keyword, e.g. drop-shadow/50) ignored its opacity modifier and always rendered with the theme's default alpha instead.

In createUtilities's drop-shadow handler (packages/tailwindcss/src/utilities.ts), the !candidate.value branch (bare drop-shadow) correctly computed the alpha-adjusted shadow into --tw-drop-shadow-size, but then unconditionally overwrote --tw-drop-shadow — the variable actually referenced by filter: var(--tw-drop-shadow, ) — with the raw, unmodified theme value, discarding the alpha entirely.

Every sibling branch (arbitrary value/color, and the named-size branch, e.g. drop-shadow-lg/50) already handles this correctly by branching on whether a modifier alpha is present and pointing --tw-drop-shadow at var(--tw-drop-shadow-size) in that case. This PR applies the same branch to the bare drop-shadow utility.

Before:

.drop-shadow\/50 {
  --tw-drop-shadow-alpha: 50%;
  --tw-drop-shadow-size: drop-shadow(0 1px 2px var(--tw-drop-shadow-color, oklab(0% 0 0 / .5))) drop-shadow(0 1px 1px var(--tw-drop-shadow-color, oklab(0% 0 0 / .5)));
  --tw-drop-shadow: drop-shadow(0 1px 2px #0000001a) drop-shadow(0 1px 1px #0000000f); /* still the theme default alpha, not 50% */
  filter: ... var(--tw-drop-shadow, );
}

After:

.drop-shadow\/50 {
  --tw-drop-shadow-alpha: 50%;
  --tw-drop-shadow-size: drop-shadow(0 1px 2px var(--tw-drop-shadow-color, oklab(0% 0 0 / .5))) drop-shadow(0 1px 1px var(--tw-drop-shadow-color, oklab(0% 0 0 / .5)));
  --tw-drop-shadow: var(--tw-drop-shadow-size);
  filter: ... var(--tw-drop-shadow, );
}

Test plan

• The existing filter test in packages/tailwindcss/src/utilities.test.ts already exercises drop-shadow/25 and drop-shadow/12.5; its inline snapshot previously asserted the buggy (unmodified-alpha) output. Updated the snapshot to reflect the corrected behavior via npx vitest run packages/tailwindcss/src/utilities.test.ts -t "^filter$" -u, and confirmed the diff only changes --tw-drop-shadow: drop-shadow(var(--drop-shadow)) → --tw-drop-shadow: var(--tw-drop-shadow-size) for the two alpha-modified cases.
• npx vitest run packages/tailwindcss/src/utilities.test.ts — all 398 tests pass.
• npx vitest run packages/tailwindcss/src/intellisense.test.ts packages/tailwindcss/src/index.test.ts — all 277 tests pass (no regressions in related suites).
• npx prettier --check packages/tailwindcss/src/utilities.ts packages/tailwindcss/src/utilities.test.ts — passes.
• npx tsc --noEmit — no new type errors introduced by this change.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Configuration used: Repository UI

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Run ID: 68bea289-b6ec-4142-b721-72fb7ade925f

📥 Commits

Reviewing files that changed from the base of the PR and between 90f8ff4 and 98c8ffe.

📒 Files selected for processing (3)

• CHANGELOG.md
• packages/tailwindcss/src/utilities.test.ts
• packages/tailwindcss/src/utilities.ts

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Walkthrough

Updated named drop-shadow utilities with opacity modifiers to derive --tw-drop-shadow from the alpha-replaced --tw-drop-shadow-size variable. Updated tests for 12.5% and 25% variants. Added an Unreleased changelog entry for size-less drop-shadow opacity modifiers.

Merge Risk: ⚪ Minimal · up to 98c8f

This change makes opacity modifiers work correctly for size-less drop-shadow utilities without altering other shadow behavior; no actionable merge-blocking risk remains 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 change: fixing opacity modifiers for bare drop-shadow utilities when no size is specified.
Description check	✅ Passed	The description directly explains the bug, the implementation change, the affected variables, the test updates, 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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[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge with no actionable correctness, security, or quality issues identified.

The changed branch correctly activates the already-computed alpha-adjusted drop-shadow value and follows the established implementation used for named drop-shadow sizes.

_{Reviews (1): Last reviewed commit: "Add changelog entry for drop-shadow opac..." | Re-trigger Greptile}