Fix negation of theme() in arbitrary values

[snaptopixel]

Problem

Using a negative modifier with theme() inside an arbitrary value produces no CSS output.

• ✅ ms-[theme(margin.1)] — works
• ✅ -ms-[10px] — works
• ❌ -ms-[theme(margin.1)] — no output

Cause

negateValue() in src/util/negateValue.js doesn't recognize theme() as a negatable function. It falls through all conditions and returns undefined, causing the utility to be silently dropped.

Fix

Added 'theme' to the numericFunctions list so theme() values get wrapped in calc(... * -1), which the PostCSS theme() resolver then processes downstream.

Tests

• Unit test (negateValue.test.js): negateValue('theme(margin.1)') returns calc(theme(margin.1) * -1)
• Integration test (arbitrary-values.test.js): -mt-[theme(spacing.1)] produces margin-top: -0.25rem

[RobinMalfait]

Edit: This is for Tailwind CSS v3.

Hey! Thanks for the PR, but where do you see this issue? This should work as-is today already:

https://play.tailwindcss.com/bGXXIU9Wai

[RobinMalfait]

Thanks!

Will be available in the next v3 release.

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge, with focused implementation and end-to-end coverage for the reported failure.

The changed function now preserves theme() through negation as a valid calc expression, after which the existing resolver substitutes the configured numeric value; no concrete valid input was found that regresses because of this change.

_{Reviews (1): Last reviewed commit: "update changelog" | Re-trigger Greptile}

[snaptopixel]

Thanks for merging @RobinMalfait!