Fix parsing url(…) with special characters such as ; or {} (#14879)

This PR fixes an issue where some special characters (with an actual
meaning CSS) were used inside of the `url(…)` function, would result in
incorrectly parsed CSS.

For example, when we encounter a `{`, then we would start a new "block"
for nesting purposes. If we encounter an `}`, then the block would end.
If we encounter a `;`, then that would be the end of a declaration.

All of that is true, unless we are in a `url(…)` function. In that case,
we should ignore all of those characters and treat them as part of the
URL.

This is only an issue because:

1. We are allowed to use these characters in URLs.
2. We can write an url inside `url(…)` without quotes. With quotes, this
would not be an issue.

---------

Co-authored-by: Philipp Spiess <hello@philippspiess.com>

CHANGELOG.md

@@ -20,6 +20,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fix crash when using `@source` containing `..` ([#14831](https://github.com/tailwindlabs/tailwindcss/pull/14831))
 - Ensure instances of the same variant with different values are always sorted deterministically (e.g. `data-focus:flex` and `data-active:flex`) ([#14835](https://github.com/tailwindlabs/tailwindcss/pull/14835))
 - Ensure `--inset-ring=*` and `--inset-shadow-*` variables are ignored by `inset-*` utilities ([#14855](https://github.com/tailwindlabs/tailwindcss/pull/14855))
+- Ensure `url(…)` containing special characters such as `;` or `{}` end up in one declaration ([#14879](https://github.com/tailwindlabs/tailwindcss/pull/14879))
 - _Upgrade (experimental)_: Install `@tailwindcss/postcss` next to `tailwindcss` ([#14830](https://github.com/tailwindlabs/tailwindcss/pull/14830))
 - _Upgrade (experimental)_: Remove whitespace around `,` separator when print arbitrary values ([#14838](https://github.com/tailwindlabs/tailwindcss/pull/14838))
 

packages/tailwindcss/src/css-parser.test.ts

@@ -505,6 +505,59 @@ describe.each(['Unix', 'Windows'])('Line endings: %s', (lineEndings) => {
         },
       ])
     })
+
+    it('should parse url(…) without quotes and special characters such as `;`, `{}`, and `[]`', () => {
+      expect(
+        parse(css`
+          .foo {
+            /* ';' should be valid inside the 'url(…)' function */
+            background: url(data:image/png;base64,abc==);
+
+            /* '{', '}', '[' and ']' should be valid inside the 'url(…)' function */
+            /* '{' and '}' should not start a new block (nesting) */
+            background: url(https://example-image-search.org?q={query;limit=5}&ids=[1,2,3]);
+
+            /* '{' and '}' don't need to be balanced */
+            background: url(https://example-image-search.org?curlies=}});
+
+            /* '(' and ')' are not valid, unless we are in a string with quotes */
+            background: url('https://example-image-search.org?q={query;limit=5}&ids=[1,2,3]&format=(png|jpg)');
+          }
+        `),
+      ).toEqual([
+        {
+          kind: 'rule',
+          selector: '.foo',
+          nodes: [
+            {
+              kind: 'declaration',
+              property: 'background',
+              value: 'url(data:image/png;base64,abc==)',
+              important: false,
+            },
+            {
+              kind: 'declaration',
+              property: 'background',
+              value: 'url(https://example-image-search.org?q={query;limit=5}&ids=[1,2,3])',
+              important: false,
+            },
+            {
+              kind: 'declaration',
+              property: 'background',
+              value: 'url(https://example-image-search.org?curlies=}})',
+              important: false,
+            },
+            {
+              kind: 'declaration',
+              property: 'background',
+              value:
+                "url('https://example-image-search.org?q={query;limit=5}&ids=[1,2,3]&format=(png|jpg)')",
+              important: false,
+            },
+          ],
+        },
+      ])
+    })
   })
 
   describe('selectors', () => {

packages/tailwindcss/src/css-parser.ts

@@ -331,7 +331,10 @@ export function parse(input: string) {
     // }
     // ```
     //
-    else if (currentChar === SEMICOLON) {
+    else if (
+      currentChar === SEMICOLON &&
+      closingBracketStack[closingBracketStack.length - 1] !== ')'
+    ) {
       let declaration = parseDeclaration(buffer)
       if (parent) {
         parent.nodes.push(declaration)
@@ -343,7 +346,10 @@ export function parse(input: string) {
     }
 
     // Start of a block.
-    else if (currentChar === OPEN_CURLY) {
+    else if (
+      currentChar === OPEN_CURLY &&
+      closingBracketStack[closingBracketStack.length - 1] !== ')'
+    ) {
       closingBracketStack += '}'
 
       // At this point `buffer` should resemble a selector or an at-rule.
@@ -368,7 +374,10 @@ export function parse(input: string) {
     }
 
     // End of a block.
-    else if (currentChar === CLOSE_CURLY) {
+    else if (
+      currentChar === CLOSE_CURLY &&
+      closingBracketStack[closingBracketStack.length - 1] !== ')'
+    ) {
       if (closingBracketStack === '') {
         throw new Error('Missing opening {')
       }
@@ -456,6 +465,22 @@ export function parse(input: string) {
       node = null
     }
 
+    // `(`
+    else if (currentChar === OPEN_PAREN) {
+      closingBracketStack += ')'
+      buffer += '('
+    }
+
+    // `)`
+    else if (currentChar === CLOSE_PAREN) {
+      if (closingBracketStack[closingBracketStack.length - 1] !== ')') {
+        throw new Error('Missing opening (')
+      }
+
+      closingBracketStack = closingBracketStack.slice(0, -1)
+      buffer += ')'
+    }
+
     // Any other character is part of the current node.
     else {
       // Skip whitespace at the start of a new node.