Don’t crash when regex is missing a capture group

Author: thecrypticace

packages/tailwindcss-language-service/src/util/classes.test.ts

@@ -160,12 +160,52 @@ let table: TestRecord[] = [
 
   // Edge cases
   {
-    name: 'regex matches empty string',
+    name: 'container regex matches empty string',
     text: `let _ = ""`,
     cursor: 9,
     filters: [['(?<=")(\\w*)(?=")']],
     expected: [{ classList: '', range: [9, 9] }],
   },
+
+  {
+    name: 'container regex matches empty string (no cursor)',
+    text: `let _ = ""`,
+    cursor: null,
+    filters: [['(?<=")(\\w*)(?=")']],
+    expected: [{ classList: '', range: [9, 9] }],
+  },
+
+  {
+    name: 'class regex matches empty string',
+    text: `let _ = clsx("")`,
+    cursor: 14,
+    filters: [['clsx\\(([^)]*)\\)', '(?<=")([^"]*)(?<=")']],
+    expected: [{ classList: '', range: [14, 14] }],
+  },
+
+  {
+    name: 'class regex matches empty string (no cursor)',
+    text: `let _ = clsx("")`,
+    cursor: null,
+    filters: [['clsx\\(([^)]*)\\)', '(?<=")([^"]*)(?<=")']],
+    expected: [{ classList: '', range: [14, 14] }, { classList: '', range: [15, 15] }],
+  },
+
+  {
+    name: 'container regex is missing a capture group',
+    text: `let _ = ""`,
+    cursor: null,
+    filters: [['(?<=")\\w*(?=")']],
+    expected: [],
+  },
+
+  {
+    name: 'class regex is missing a capture group',
+    text: `let _ = clsx("")`,
+    cursor: null,
+    filters: [['clsx\\(([^)]*)\\)', '"[^"]*"']],
+    expected: [],
+  },
 ]
 
 test.each(table)('customClassesIn: $name', ({ text, cursor, filters, expected }) => {

packages/tailwindcss-language-service/src/util/classes.ts

@@ -34,6 +34,12 @@ function *matchesIn(
   cursor: number | null,
 ): Iterable<ClassMatch> {
   for (let containerMatch of text.matchAll(containerRegex)) {
+    // Don't crash when there's no capture group
+    if (containerMatch[1] === undefined) {
+      console.warn(`Regex /${containerRegex.source}/ must have exactly one capture group`)
+      continue
+    }
+
     const matchStart = containerMatch.indices[1][0]
     const matchEnd = matchStart + containerMatch[1].length
 
@@ -54,6 +60,12 @@ function *matchesIn(
 
     // Handle class matches inside the "container"
     for (let classMatch of containerMatch[1].matchAll(classRegex)) {
+      // Don't crash when there's no capture group
+      if (classMatch[1] === undefined) {
+        console.warn(`Regex /${classRegex.source}/ must have exactly one capture group`)
+        continue
+      }
+
       const classMatchStart = matchStart + classMatch.indices[1][0]
       const classMatchEnd = classMatchStart + classMatch[1].length