Handle theme keys with slashes when using theme() in CSS

CHANGELOG.md

@@ -7,15 +7,18 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-- Nothing yet!
+### Fixed
+
+- Fix usage on Node 12.x ([b4e637e](https://github.com/tailwindlabs/tailwindcss/commit/b4e637e2e096a9d6f2210efba9541f6fd4f28e56))
+- Handle theme keys with slashes when using `theme()` in CSS ([#8831](https://github.com/tailwindlabs/tailwindcss/pull/8831))
 
 ## [3.1.5] - 2022-07-07
 
 ### Added
 
 - Support configuring a default `font-weight` for each font size utility ([#8763](https://github.com/tailwindlabs/tailwindcss/pull/8763))
 - Add support for alpha values in safe list ([#8774](https://github.com/tailwindlabs/tailwindcss/pull/8774))
- 
+
 ### Fixed
 
 - Improve types to support fallback values in the CSS-in-JS syntax used in plugin APIs ([#8762](https://github.com/tailwindlabs/tailwindcss/pull/8762))

src/lib/evaluateTailwindFunctions.js

@@ -157,26 +157,52 @@ let nodeTypePropertyMap = {
   decl: 'value',
 }
 
-export default function ({ tailwindConfig: config }) {
-  let functions = {
-    theme: (node, path, ...defaultValue) => {
-      // Strip quotes from beginning and end of string
-      // This allows the alpha value to be present inside of quotes
-      path = path.replace(/^['"]+|['"]+$/g, '')
+/**
+ * @param {string} path
+ * @returns {Iterable<[path: string, alpha: string|undefined]>}
+ */
+function* toPaths(path) {
+  // Strip quotes from beginning and end of string
+  // This allows the alpha value to be present inside of quotes
+  path = path.replace(/^['"]+|['"]+$/g, '')
 
-      let matches = path.match(/^([^\s]+)(?![^\[]*\])(?:\s*\/\s*([^\/\s]+))$/)
-      let alpha = undefined
+  let matches = path.match(/^([^\s]+)(?![^\[]*\])(?:\s*\/\s*([^\/\s]+))$/)
+  let alpha = undefined
 
-      if (matches) {
-        path = matches[1]
-        alpha = matches[2]
-      }
+  yield [path, undefined]
+
+  if (matches) {
+    path = matches[1]
+    alpha = matches[2]
+
+    yield [path, alpha]
+  }
+}
 
-      let { isValid, value, error } = validatePath(
+/**
+ *
+ * @param {any} config
+ * @param {string} path
+ * @param {any} defaultValue
+ */
+function resolvePath(config, path, defaultValue) {
+  const results = Array.from(toPaths(path)).map(([path, alpha]) => {
+    return Object.assign(validatePath(config, path, defaultValue, { opacityValue: alpha }), {
+      resolvedPath: path,
+      alpha,
+    })
+  })
+
+  return results.find((result) => result.isValid) ?? results[0]
+}
+
+export default function ({ tailwindConfig: config }) {
+  let functions = {
+    theme: (node, path, ...defaultValue) => {
+      let { isValid, value, error, alpha } = resolvePath(
         config,
         path,
-        defaultValue.length ? defaultValue : undefined,
-        { opacityValue: alpha }
+        defaultValue.length ? defaultValue : undefined
       )
 
       if (!isValid) {

tests/evaluateTailwindFunctions.test.js

@@ -1135,3 +1135,51 @@ test('Theme functions with alpha with quotes value around color only', () => {
     expect(result.warnings().length).toBe(0)
   })
 })
+
+it('can find values with slashes in the theme key while still allowing for alpha values ', () => {
+  let input = css`
+    .foo00 {
+      color: theme(colors.foo-5);
+    }
+    .foo01 {
+      color: theme(colors.foo-5/10);
+    }
+    .foo02 {
+      color: theme(colors.foo-5/10/25);
+    }
+    .foo03 {
+      color: theme(colors.foo-5 / 10);
+    }
+    .foo04 {
+      color: theme(colors.foo-5/10 / 25);
+    }
+  `
+
+  return runFull(input, {
+    theme: {
+      colors: {
+        'foo-5': '#050000',
+        'foo-5/10': '#051000',
+        'foo-5/10/25': '#051025',
+      },
+    },
+  }).then((result) => {
+    expect(result.css).toMatchCss(css`
+      .foo00 {
+        color: #050000;
+      }
+      .foo01 {
+        color: #051000;
+      }
+      .foo02 {
+        color: #051025;
+      }
+      .foo03 {
+        color: rgb(5 0 0 / 10);
+      }
+      .foo04 {
+        color: rgb(5 16 0 / 25);
+      }
+    `)
+  })
+})