Ensure arbitrary values only support valid values

src/jit/lib/setupContextUtils.js

@@ -125,6 +125,64 @@ function withIdentifiers(styles) {
   })
 }
 
+let matchingBrackets = new Map([
+  ['{', '}'],
+  ['[', ']'],
+  ['(', ')'],
+])
+let inverseMatchingBrackets = new Map(
+  Array.from(matchingBrackets.entries()).map(([k, v]) => [v, k])
+)
+
+let quotes = new Set(['"', "'", '`'])
+
+// Arbitrary values must contain balanced brackets (), [] and {}. Escaped
+// values don't count, and brackets inside quotes also don't count.
+//
+// E.g.: w-[this-is]w-[weird-and-invalid]
+// E.g.: w-[this-is\\]w-\\[weird-but-valid]
+// E.g.: content-['this-is-also-valid]-weirdly-enough']
+function isValidArbitraryValue(value) {
+  let stack = []
+  let inQuotes = false
+
+  for (let i = 0; i < value.length; i++) {
+    let char = value[i]
+
+    // Non-escaped quotes allow us to "allow" anything in between
+    if (quotes.has(char) && value[i - 1] !== '\\') {
+      inQuotes = !inQuotes
+    }
+
+    if (inQuotes) continue
+    if (value[i - 1] === '\\') continue // Escaped
+
+    if (matchingBrackets.has(char)) {
+      stack.push(char)
+    } else if (inverseMatchingBrackets.has(char)) {
+      let inverse = inverseMatchingBrackets.get(char)
+
+      // Nothing to pop from, therefore it is unbalanced
+      if (stack.length <= 0) {
+        return false
+      }
+
+      // Popped value must match the inverse value, otherwise it is unbalanced
+      if (stack.pop() !== inverse) {
+        return false
+      }
+    }
+  }
+
+  // If there is still something on the stack, it is also unbalanced
+  if (stack.length > 0) {
+    return false
+  }
+
+  // All good, totally balanced!
+  return true
+}
+
 function buildPluginApi(tailwindConfig, context, { variantList, variantMap, offsets }) {
   function getConfigValue(path, defaultValue) {
     return path ? dlv(tailwindConfig, path, defaultValue) : tailwindConfig
@@ -273,6 +331,10 @@ function buildPluginApi(tailwindConfig, context, { variantList, variantMap, offs
             return []
           }
 
+          if (!isValidArbitraryValue(value)) {
+            return []
+          }
+
           let includedRules = []
           let ruleSets = []
             .concat(

tests/jit/arbitrary-values.test.css

@@ -93,6 +93,28 @@
 .w-\[calc\(100\%\/3-1rem\*2\)\] {
   width: calc(100% / 3 - 1rem * 2);
 }
+.w-\[\{\}\] {
+  width: {
+  }
+}
+.w-\[\{\{\}\}\] {
+  width: {
+     {
+    }
+  }
+}
+.w-\[\(\)\] {
+  width: ();
+}
+.w-\[\(\(\)\)\] {
+  width: (());
+}
+.w-\[\'\)\(\)\'\] {
+  width: ')()';
+}
+.w-\[\'\}\{\}\'\] {
+  width: '}{}';
+}
 .min-w-\[3\.23rem\] {
   min-width: 3.23rem;
 }

tests/jit/arbitrary-values.test.html

@@ -116,5 +116,33 @@
     <div class="delay-[var(--delay)]"></div>
     <div class="content-['hello']"></div>
     <div class="content-[attr(content-before)]"></div>
+
+    <!-- Balancing issues, this is not checking the validity of the actual value, but purely syntax-wise -->
+    <div class="w-[do-not-generate-this]w-[it-is-invalid-syntax]"></div><!-- INVALID -->
+    <div class="grid-cols-[[linename],1fr,auto]"></div><!-- VALID -->
+    <div class="w-[{}]"></div><!-- VALID -->
+    <div class="w-[{{}}]"></div><!-- VALID -->
+    <div class="w-[[]]"></div><!-- VALID -->
+    <div class="w-[[[]]]"></div><!-- VALID -->
+    <div class="w-[()]"></div><!-- VALID -->
+    <div class="w-[(())]"></div><!-- VALID -->
+    <div class="w-[][]"></div><!-- INVALID -->
+    <div class="w-[)(]"></div><!-- INVALID -->
+    <div class="w-[}{]"></div><!-- INVALID -->
+    <div class="w-[][]]"></div><!-- INVALID -->
+    <div class="w-[)()]"></div><!-- INVALID -->
+    <div class="w-[}{}]"></div><!-- INVALID -->
+    <div class="w-['][]']"></div><!-- VALID -->
+    <div class="w-[')()']"></div><!-- VALID -->
+    <div class="w-['}{}']"></div><!-- VALID -->
+    <div class="w-[[']']]"></div><!-- VALID -->
+    <div class="w-[(')')]"></div><!-- VALID -->
+    <div class="w-[{'}'}]"></div><!-- VALID -->
+    <div class="w-[{[}]]"></div><!-- INVALID -->
+    <div class="w-[[{]}]"></div><!-- INVALID -->
+    <div class="w-[{(})]"></div><!-- INVALID -->
+    <div class="w-[({)}]"></div><!-- INVALID -->
+    <div class="w-[([)]]"></div><!-- INVALID -->
+    <div class="w-[[(])]"></div><!-- INVALID -->
   </body>
 </html>