From 9b97f9bffa31a83651617e64f3ee68454349ce5c Mon Sep 17 00:00:00 2001
From: Jordan Pittman <jordan@cryptica.me>
Date: Fri, 9 May 2025 15:17:23 -0400
Subject: [PATCH 1/4] Add test

---
 .../src/util/find.test.ts                     | 81 ++++++++++++++++++-
 1 file changed, 79 insertions(+), 2 deletions(-)

diff --git a/packages/tailwindcss-language-service/src/util/find.test.ts b/packages/tailwindcss-language-service/src/util/find.test.ts
index 170217c0..e4003cf3 100644
--- a/packages/tailwindcss-language-service/src/util/find.test.ts
+++ b/packages/tailwindcss-language-service/src/util/find.test.ts
@@ -1,6 +1,16 @@
 import { test } from 'vitest'
-import { findClassListsInHtmlRange, findClassNameAtPosition } from './find'
-import { js, html, pug, createDocument } from './test-utils'
+import {
+  findClassListsInHtmlRange,
+  findClassNameAtPosition,
+  findHelperFunctionsInDocument,
+} from './find'
+import { js, html, pug, createDocument, css } from './test-utils'
+import type { Range } from 'vscode-languageserver-textdocument'
+
+const range = (startLine: number, startCol: number, endLine: number, endCol: number): Range => ({
+  start: { line: startLine, character: startCol },
+  end: { line: endLine, character: endCol },
+})
 
 test('class regex works in astro', async ({ expect }) => {
   let file = createDocument({
@@ -875,3 +885,70 @@ test('Can find class name inside JS/TS functions in <script> tags (Svelte)', asy
     },
   })
 })
+
+test('Can find helper functions in CSS', async ({ expect }) => {
+  let file = createDocument({
+    name: 'file.css',
+    lang: 'css',
+    settings: {
+      tailwindCSS: {
+        classFunctions: ['clsx'],
+      },
+    },
+    content: `
+      .a { color: theme(foo); }
+      .a { color: theme(foo, default); }
+      .a { color: theme("foo"); }
+      .a { color: theme("foo", default); }
+      .a { color: theme(foo / 0.5); }
+      .a { color: theme(foo / 0.5, default); }
+      .a { color: theme("foo" / 0.5); }
+      .a { color: theme("foo" / 0.5, default); }
+    `,
+  })
+
+  let fns = findHelperFunctionsInDocument(file.state, file.doc)
+
+  expect(fns).toEqual([
+    {
+      helper: 'theme',
+      path: 'foo',
+      ranges: { full: range(1, 24, 1, 27), path: range(1, 24, 1, 27) },
+    },
+    {
+      helper: 'theme',
+      path: 'foo',
+      ranges: { full: range(2, 24, 2, 36), path: range(2, 24, 2, 27) },
+    },
+    {
+      helper: 'theme',
+      path: 'foo',
+      ranges: { full: range(3, 24, 3, 29), path: range(3, 25, 3, 28) },
+    },
+    {
+      helper: 'theme',
+      path: 'foo',
+      ranges: { full: range(4, 24, 4, 38), path: range(4, 25, 4, 28) },
+    },
+    {
+      helper: 'theme',
+      path: 'foo',
+      ranges: { full: range(5, 24, 5, 33), path: range(5, 24, 5, 27) },
+    },
+    {
+      helper: 'theme',
+      path: 'foo',
+      ranges: { full: range(6, 24, 6, 42), path: range(6, 24, 6, 27) },
+    },
+    {
+      helper: 'theme',
+      path: 'foo',
+      ranges: { full: range(7, 24, 7, 35), path: range(7, 25, 7, 28) },
+    },
+    {
+      helper: 'theme',
+      path: 'foo',
+      ranges: { full: range(8, 24, 8, 44), path: range(8, 25, 8, 28) },
+    },
+  ])
+})

From 90ee094c7a57efa2dd1edf2a487be07c0e7309b0 Mon Sep 17 00:00:00 2001
From: Jordan Pittman <jordan@cryptica.me>
Date: Fri, 9 May 2025 16:02:52 -0400
Subject: [PATCH 2/4] Add failing tests for nested invocations

---
 .../src/util/find.test.ts                     | 92 +++++++++++++++++++
 1 file changed, 92 insertions(+)

diff --git a/packages/tailwindcss-language-service/src/util/find.test.ts b/packages/tailwindcss-language-service/src/util/find.test.ts
index e4003cf3..9c65f23d 100644
--- a/packages/tailwindcss-language-service/src/util/find.test.ts
+++ b/packages/tailwindcss-language-service/src/util/find.test.ts
@@ -904,6 +904,16 @@ test('Can find helper functions in CSS', async ({ expect }) => {
       .a { color: theme(foo / 0.5, default); }
       .a { color: theme("foo" / 0.5); }
       .a { color: theme("foo" / 0.5, default); }
+
+      /* nested invocations */
+      .a { color: from-config(theme(foo)); }
+      .a { color: from-config(theme(foo, default)); }
+      .a { color: from-config(theme("foo")); }
+      .a { color: from-config(theme("foo", default)); }
+      .a { color: from-config(theme(foo / 0.5)); }
+      .a { color: from-config(theme(foo / 0.5, default)); }
+      .a { color: from-config(theme("foo" / 0.5)); }
+      .a { color: from-config(theme("foo" / 0.5, default)); }
     `,
   })
 
@@ -950,5 +960,87 @@ test('Can find helper functions in CSS', async ({ expect }) => {
       path: 'foo',
       ranges: { full: range(8, 24, 8, 44), path: range(8, 25, 8, 28) },
     },
+
+    // Nested
+    {
+      helper: 'config',
+      path: 'theme(foo)',
+      ranges: { full: range(11, 30, 11, 40), path: range(11, 30, 11, 40) },
+    },
+    {
+      helper: 'theme',
+      path: 'foo',
+      ranges: { full: range(11, 36, 11, 39), path: range(11, 36, 11, 39) },
+    },
+    {
+      helper: 'config',
+      path: 'theme(foo, default)',
+      ranges: { full: range(12, 30, 12, 49), path: range(12, 30, 12, 49) },
+    },
+    {
+      helper: 'theme',
+      path: 'foo',
+      ranges: { full: range(12, 36, 12, 48), path: range(12, 36, 12, 39) },
+    },
+    {
+      helper: 'config',
+      path: 'theme("foo")',
+      ranges: { full: range(13, 30, 13, 42), path: range(13, 30, 13, 42) },
+    },
+    {
+      helper: 'theme',
+      path: 'foo',
+      ranges: { full: range(13, 36, 13, 41), path: range(13, 37, 13, 40) },
+    },
+    {
+      helper: 'config',
+      path: 'theme("foo", default)',
+      ranges: { full: range(14, 30, 14, 51), path: range(14, 30, 14, 51) },
+    },
+    {
+      helper: 'theme',
+      path: 'foo',
+      ranges: { full: range(14, 36, 14, 50), path: range(14, 37, 14, 40) },
+    },
+    {
+      helper: 'config',
+      path: 'theme(foo / 0.5)',
+      ranges: { full: range(15, 30, 15, 46), path: range(15, 30, 15, 46) },
+    },
+    {
+      helper: 'theme',
+      path: 'foo',
+      ranges: { full: range(15, 36, 15, 45), path: range(15, 36, 15, 39) },
+    },
+    {
+      helper: 'config',
+      path: 'theme(foo / 0.5, default)',
+      ranges: { full: range(16, 30, 16, 55), path: range(16, 30, 16, 55) },
+    },
+    {
+      helper: 'theme',
+      path: 'foo',
+      ranges: { full: range(16, 36, 16, 54), path: range(16, 36, 16, 39) },
+    },
+    {
+      helper: 'config',
+      path: 'theme("foo" / 0.5)',
+      ranges: { full: range(17, 30, 17, 48), path: range(17, 30, 17, 48) },
+    },
+    {
+      helper: 'theme',
+      path: 'foo',
+      ranges: { full: range(17, 36, 17, 47), path: range(17, 37, 17, 40) },
+    },
+    {
+      helper: 'config',
+      path: 'theme("foo" / 0.5, default)',
+      ranges: { full: range(18, 30, 18, 57), path: range(18, 30, 18, 57) },
+    },
+    {
+      helper: 'theme',
+      path: 'foo',
+      ranges: { full: range(18, 36, 18, 56), path: range(18, 37, 18, 40) },
+    },
   ])
 })

From 81c611ee3c989fa0ca95bba2f1beaa33bd7f6eab Mon Sep 17 00:00:00 2001
From: Jordan Pittman <jordan@cryptica.me>
Date: Fri, 9 May 2025 16:03:42 -0400
Subject: [PATCH 3/4] Handle balanced parens when searching for helper
 functions

---
 .../src/util/find.ts                          | 166 ++++++++++++++----
 1 file changed, 132 insertions(+), 34 deletions(-)

diff --git a/packages/tailwindcss-language-service/src/util/find.ts b/packages/tailwindcss-language-service/src/util/find.ts
index 53ad7195..11f5946f 100644
--- a/packages/tailwindcss-language-service/src/util/find.ts
+++ b/packages/tailwindcss-language-service/src/util/find.ts
@@ -403,13 +403,12 @@ export function findHelperFunctionsInRange(
   doc: TextDocument,
   range?: Range,
 ): DocumentHelperFunction[] {
-  const text = getTextWithoutComments(doc, 'css', range)
-  let matches = findAll(
-    /(?<prefix>[\W])(?<helper>config|theme|--theme|var)(?<innerPrefix>\(\s*)(?<path>[^)]*?)\s*\)/g,
-    text,
-  )
+  let text = getTextWithoutComments(doc, 'css', range)
+
+  // Find every instance of a helper function
+  let matches = findAll(/\b(?<helper>config|theme|--theme|var)\(/g, text)
 
-  // Eliminate matches that are on an `@import`
+  // Eliminate matches that are attached to an `@import`
   matches = matches.filter((match) => {
     // Scan backwards to see if we're in an `@import` statement
     for (let i = match.index - 1; i >= 0; i--) {
@@ -427,58 +426,157 @@ export function findHelperFunctionsInRange(
     return true
   })
 
-  return matches.map((match) => {
-    let quotesBefore = ''
-    let path = match.groups.path
-    let commaIndex = getFirstCommaIndex(path)
-    if (commaIndex !== null) {
-      path = path.slice(0, commaIndex).trimEnd()
-    }
-    path = path.replace(/['"]+$/, '').replace(/^['"]+/, (m) => {
-      quotesBefore = m
-      return ''
-    })
-    let matches = path.match(/^([^\s]+)(?![^\[]*\])(?:\s*\/\s*([^\/\s]+))$/)
-    if (matches) {
-      path = matches[1]
+  let fns: DocumentHelperFunction[] = []
+
+  // Collect the first argument of each fn accounting for balanced params
+  const COMMA = 0x2c
+  const SLASH = 0x2f
+  const BACKSLASH = 0x5c
+  const OPEN_PAREN = 0x28
+  const CLOSE_PAREN = 0x29
+  const DOUBLE_QUOTE = 0x22
+  const SINGLE_QUOTE = 0x27
+
+  let len = text.length
+
+  for (let match of matches) {
+    let argsStart = match.index + match[0].length
+    let argsEnd = null
+    let pathStart = argsStart
+    let pathEnd = null
+    let depth = 1
+
+    // Scan until we find a `,` or balanced `)` not in quotes
+    for (let idx = argsStart; idx < len; ++idx) {
+      let char = text.charCodeAt(idx)
+
+      if (char === BACKSLASH) {
+        idx += 1
+      }
+
+      //
+      else if (char === SINGLE_QUOTE || char === DOUBLE_QUOTE) {
+        while (++idx < len) {
+          let nextChar = text.charCodeAt(idx)
+          if (nextChar === BACKSLASH) {
+            idx += 1
+            continue
+          }
+          if (nextChar === char) break
+        }
+      }
+
+      //
+      else if (char === OPEN_PAREN) {
+        depth += 1
+      }
+
+      //
+      else if (char === CLOSE_PAREN) {
+        depth -= 1
+
+        if (depth === 0) {
+          pathEnd ??= idx
+          argsEnd = idx
+          break
+        }
+      }
+
+      //
+      else if (char === COMMA && depth === 1) {
+        pathEnd ??= idx
+      }
     }
-    path = path.replace(/['"]*\s*$/, '')
 
-    let startIndex =
-      match.index +
-      match.groups.prefix.length +
-      match.groups.helper.length +
-      match.groups.innerPrefix.length
+    if (argsEnd === null) continue
 
-    let helper: 'config' | 'theme' | 'var' = 'config'
+    let helper: 'config' | 'theme' | 'var'
 
     if (match.groups.helper === 'theme' || match.groups.helper === '--theme') {
       helper = 'theme'
     } else if (match.groups.helper === 'var') {
       helper = 'var'
+    } else if (match.groups.helper === 'config') {
+      helper = 'config'
+    } else {
+      continue
     }
 
-    return {
+    let path = text.slice(pathStart, pathEnd)
+
+    // Skip leading/trailing whitespace
+    pathStart += path.match(/^\s+/)?.length ?? 0
+    pathEnd -= path.match(/\s+$/)?.length ?? 0
+
+    // Skip leading/trailing quotes
+    let quoteStart = path.match(/^['"]+/)?.length ?? 0
+    let quoteEnd = path.match(/['"]+$/)?.length ?? 0
+
+    if (quoteStart && quoteEnd) {
+      pathStart += quoteStart
+      pathEnd -= quoteEnd
+    }
+
+    // Clip to the top-level slash
+    depth = 1
+    for (let idx = pathStart; idx < pathEnd; ++idx) {
+      let char = text.charCodeAt(idx)
+      if (char === BACKSLASH) {
+        idx += 1
+      } else if (char === OPEN_PAREN) {
+        depth += 1
+      } else if (char === CLOSE_PAREN) {
+        depth -= 1
+      } else if (char === SLASH && depth === 1) {
+        pathEnd = idx
+      }
+    }
+
+    // Re-slice
+    path = text.slice(pathStart, pathEnd)
+
+    // Skip leading/trailing whitespace
+    //
+    // This can happen if we've clipped the path down to before the `/`
+    pathStart += path.match(/^\s+/)?.length ?? 0
+    pathEnd -= path.match(/\s+$/)?.length ?? 0
+
+    // Re-slice
+    path = text.slice(pathStart, pathEnd)
+
+    // Skip leading/trailing quotes
+    quoteStart = path.match(/^['"]+/)?.length ?? 0
+    quoteEnd = path.match(/['"]+$/)?.length ?? 0
+
+    pathStart += quoteStart
+    pathEnd -= quoteEnd
+
+    // Re-slice
+    path = text.slice(pathStart, pathEnd)
+
+    fns.push({
       helper,
       path,
       ranges: {
         full: absoluteRange(
           {
-            start: indexToPosition(text, startIndex),
-            end: indexToPosition(text, startIndex + match.groups.path.length),
+            start: indexToPosition(text, argsStart),
+            end: indexToPosition(text, argsEnd),
           },
           range,
         ),
         path: absoluteRange(
           {
-            start: indexToPosition(text, startIndex + quotesBefore.length),
-            end: indexToPosition(text, startIndex + quotesBefore.length + path.length),
+            start: indexToPosition(text, pathStart),
+            end: indexToPosition(text, pathEnd),
           },
           range,
         ),
       },
-    }
-  })
+    })
+  }
+
+  return fns
 }
 
 export function indexToPosition(str: string, index: number): Position {

From ebfd909d2fbb3f18a7662951fdc692286cb41666 Mon Sep 17 00:00:00 2001
From: Jordan Pittman <jordan@cryptica.me>
Date: Tue, 13 May 2025 12:14:46 -0400
Subject: [PATCH 4/4] Update changelog

---
 packages/vscode-tailwindcss/CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/packages/vscode-tailwindcss/CHANGELOG.md b/packages/vscode-tailwindcss/CHANGELOG.md
index cea2da55..b0edc93d 100644
--- a/packages/vscode-tailwindcss/CHANGELOG.md
+++ b/packages/vscode-tailwindcss/CHANGELOG.md
@@ -10,6 +10,7 @@
 - Calculate swatches for HSL colors with angular units ([#1360](https://github.com/tailwindlabs/tailwindcss-intellisense/pull/1360))
 - Fix error when using VSCode < 1.78 ([#1353](https://github.com/tailwindlabs/tailwindcss-intellisense/pull/1353))
 - Don’t skip suggesting empty variant implementations ([#1352](https://github.com/tailwindlabs/tailwindcss-intellisense/pull/1352))
+- Handle helper function lookups in nested parens ([#1354](https://github.com/tailwindlabs/tailwindcss-intellisense/pull/1354))
 
 # 0.14.16