From ed1d5a70ac9f140bb442c3708a6a105881849a73 Mon Sep 17 00:00:00 2001
From: Radu Ursache <radu@ursache.ro>
Date: Tue, 24 Mar 2026 10:54:47 +0200
Subject: [PATCH] Fix CSS @media query parsing error in style elements

Skip unknown CSS @ rules (e.g. @media, @supports) including nested
blocks when parsing style sheets. Previously the parser would fail
when encountering @media queries, printing a parsing error to console.

The scanner now tracks brace depth to correctly skip over nested rule
blocks while continuing to parse surrounding selectors.

Closes #59
---
 DOM/Sources/Parser.XML.StyleSheet.swift    | 22 ++++++++++++
 DOM/Tests/Parser.XML.StyleSheetTests.swift | 41 ++++++++++++++++++++++
 2 files changed, 63 insertions(+)

diff --git a/DOM/Sources/Parser.XML.StyleSheet.swift b/DOM/Sources/Parser.XML.StyleSheet.swift
index 91d7fa5..c3ccae0 100644
--- a/DOM/Sources/Parser.XML.StyleSheet.swift
+++ b/DOM/Sources/Parser.XML.StyleSheet.swift
@@ -126,6 +126,9 @@ extension XMLParser.Scanner {
         if let attributes = try scanNextFontFace() {
             return (.atRule("font-face"), attributes)
         }
+        if let name = scanUnknownAtRule() {
+            return (.atRule(name), [:])
+        }
         let selectorTypes = try scanSelectorTypes()
         guard !selectorTypes.isEmpty else { return nil }
         return (.selector(selectorTypes), try scanAtttributes())
@@ -148,6 +151,25 @@ extension XMLParser.Scanner {
         return try scanAtttributes()
     }
 
+    /// Skips unknown @ rules (e.g. @media, @supports) including nested blocks.
+    /// Returns the rule name if an unknown @ rule was consumed, nil otherwise.
+    mutating func scanUnknownAtRule() -> String? {
+        guard doScanString("@") else { return nil }
+        guard let name = try? scanString(upTo: .init(charactersIn: "{")),
+              doScanString("{") else { return nil }
+        var depth = 1
+        while depth > 0 && !isEOF {
+            if doScanString("{") {
+                depth += 1
+            } else if doScanString("}") {
+                depth -= 1
+            } else {
+                _ = try? scanString(upTo: .init(charactersIn: "{}"))
+            }
+        }
+        return name.trimmingCharacters(in: .whitespacesAndNewlines)
+    }
+
     private mutating func scanNextElement() throws -> String? {
         do {
             return try scanSelectorName()
diff --git a/DOM/Tests/Parser.XML.StyleSheetTests.swift b/DOM/Tests/Parser.XML.StyleSheetTests.swift
index 9116669..3c60fc5 100644
--- a/DOM/Tests/Parser.XML.StyleSheetTests.swift
+++ b/DOM/Tests/Parser.XML.StyleSheetTests.swift
@@ -191,6 +191,47 @@ struct ParserXMLStyleSheetTests {
         )
     }
 
+    @Test
+    func skipsMediaQueries() throws {
+        let entries = try XMLParser.parseSelectorEntries(
+            """
+            g { fill: #000; }
+
+            @media (prefers-color-scheme: dark) {
+              g { fill: #fff; }
+            }
+            """
+        )
+
+        #expect(
+            entries == [
+                .element("g"): ["fill": "#000"]
+            ]
+        )
+    }
+
+    @Test
+    func skipsNestedAtRules() throws {
+        let entries = try XMLParser.parseSelectorEntries(
+            """
+            .a { fill: red; }
+            @supports (display: grid) {
+              @media (min-width: 600px) {
+                .b { fill: blue; }
+              }
+            }
+            .c { stroke: green; }
+            """
+        )
+
+        #expect(
+            entries == [
+                .class("a"): ["fill": "red"],
+                .class("c"): ["stroke": "green"]
+            ]
+        )
+    }
+
     @Test
     func parsesFontFaceEntries() throws {
         let entries = try XMLParser.parseFontFaceEntries(