Handle theme keys with slashes when using theme() in CSS (#8831)

* Fix lookup of `theme(…)` paths with slashes in them

* Update changelog

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### 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
 

src/lib/evaluateTailwindFunctions.js

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