Fix negation of theme() in arbitrary values

src/util/negateValue.js

@@ -14,7 +14,7 @@ export default function negateValue(value) {
   // var() isn't inherently a numeric function but we support it anyway
   // The trigonometric functions are omitted because you'll need to use calc(…) with them _anyway_
   // to produce generally useful results and that will be covered already
-  let numericFunctions = ['var', 'calc', 'min', 'max', 'clamp']
+  let numericFunctions = ['var', 'calc', 'min', 'max', 'clamp', 'theme']
 
   for (const fn of numericFunctions) {
     if (value.includes(`${fn}(`)) {

tests/arbitrary-values.test.js

@@ -354,6 +354,25 @@ it('should be possible to read theme values in arbitrary values (without quotes)
   })
 })
 
+it('should be possible to negate theme values in arbitrary values with negative modifier', () => {
+  let config = {
+    content: [{ raw: html`<div class="-mt-[theme(spacing.1)]"></div>` }],
+    theme: {
+      spacing: {
+        1: '0.25rem',
+      },
+    },
+  }
+
+  return run('@tailwind utilities', config).then((result) => {
+    return expect(result.css).toMatchFormattedCss(css`
+      .-mt-\[theme\(spacing\.1\)\] {
+        margin-top: -0.25rem;
+      }
+    `)
+  })
+})
+
 it('should be possible to read theme values in arbitrary values (with quotes)', () => {
   let config = {
     content: [{ raw: html`<div class="w-[theme('spacing.1')] w-[theme('spacing[0.5]')]"></div>` }],

tests/negateValue.test.js

@@ -12,3 +12,7 @@ test('values that cannot be negated become undefined', () => {
   expect(negateValue('auto')).toBeUndefined()
   expect(negateValue('cover')).toBeUndefined()
 })
+
+test('it negates theme() function calls', () => {
+  expect(negateValue('theme(margin.1)')).toEqual('calc(theme(margin.1) * -1)')
+})