Ensure spacing utilities with no value (e.g. px) don't generate CSS

packages/tailwindcss/src/utilities.test.ts

@@ -16124,6 +16124,22 @@ describe('spacing utilities', () => {
       }"
     `)
   })
+
+  test('spacing utilities must have a value', async () => {
+    let { build } = await compile(css`
+      @theme {
+        --spacing: 4px;
+      }
+      @tailwind utilities;
+    `)
+    let compiled = build(['px'])
+
+    expect(optimizeCss(compiled).trim()).toMatchInlineSnapshot(`
+      ":root {
+        --spacing: 4px;
+      }"
+    `)
+  })
 })
 
 describe('custom utilities', () => {

packages/tailwindcss/src/utilities.ts

@@ -278,7 +278,10 @@ export function createUtilities(theme: Theme) {
         // `defaultValue` (for candidates like `grow` that have no theme values)
         // or a bare theme value (like `--radius` for `rounded`). No utility
         // will ever support both of these.
-        value = desc.defaultValue ?? theme.resolve(null, desc.themeKeys ?? [])
+        value =
+          desc.defaultValue !== undefined
+            ? desc.defaultValue
+            : theme.resolve(null, desc.themeKeys ?? [])
       } else if (candidate.value.kind === 'arbitrary') {
         if (candidate.modifier) return
         value = candidate.value.value
@@ -394,6 +397,7 @@ export function createUtilities(theme: Theme) {
       themeKeys,
       supportsFractions,
       supportsNegative,
+      defaultValue: null,
       handleBareValue: ({ value }) => {
         let multiplier = theme.resolve(null, ['--spacing'])
         if (!multiplier) return null