Handle escaped characters in consumeSubQuery

Fixes #2146

CHANGES.md

@@ -40,6 +40,7 @@
   e.g.: `h1:has(+h2)`). [2137](https://github.com/jhy/jsoup/issues/2137)
 * The `:empty` selector incorrectly matched elements that started with a blank text node and were followed by 
   non-empty nodes, due to an incorrect short-circuit. [2130](https://github.com/jhy/jsoup/issues/2130) 
+* `Element.cssSelector()` would fail with "Did not find balanced marker" when building a selector for elements that had a `(` or `[` in their class names. And selectors with those characters escaped would not match as expected. [2146](https://github.com/jhy/jsoup/issues/2146)
 * Fuzz: a Stack Overflow exception could occur when resolving a crafted `<base href>` URL, in the normalizing regex. 
   [2165](https://github.com/jhy/jsoup/issues/2165)
 

src/main/java/org/jsoup/select/QueryParser.java

@@ -158,7 +158,10 @@ private String consumeSubQuery() {
                 sq.append("(").append(tq.chompBalanced('(', ')')).append(")");
             else if (tq.matches("["))
                 sq.append("[").append(tq.chompBalanced('[', ']')).append("]");
-            else
+            else if (tq.matches("\\")) { // bounce over escapes
+                sq.append(tq.consume());
+                if (!tq.isEmpty()) sq.append(tq.consume());
+            } else
                 sq.append(tq.consume());
         }
         return StringUtil.releaseBuilder(sq);

src/test/java/org/jsoup/nodes/ElementTest.java

@@ -2612,6 +2612,30 @@ void prettySerializationRoundTrips(Document.OutputSettings settings) {
         assertEquals(element, elements.first());
     }
 
+    @Test void cssSelectorWithBracket() {
+        // https://github.com/jhy/jsoup/issues/2146
+        Document doc = Jsoup.parse("<div class='a[foo]'>One</div><div class='b[bar]'>Two</div>");
+        Element div = doc.expectFirst("div");
+        String selector = div.cssSelector();
+        assertEquals("html > body > div.a\\[foo\\]", selector); // would fail with "Did not find balanced marker", consumeSubquery was not handling escapes
+
+        Elements selected = doc.select(selector);
+        assertEquals(1, selected.size());
+        assertEquals(selected.first(), div);
+    }
+
+    @Test void cssSelectorUnbalanced() {
+        // https://github.com/jhy/jsoup/issues/2146
+        Document doc = Jsoup.parse("<div class='a(foo'>One</div><div class='a-bar'>Two</div>");
+        Element div = doc.expectFirst("div");
+        String selector = div.cssSelector();
+        assertEquals("html > body > div.a\\(foo", selector);
+
+        Elements selected = doc.select(selector);
+        assertEquals(1, selected.size());
+        assertEquals(selected.first(), div);
+    }
+
     @Test void orphanSiblings() {
         Element el = new Element("div");
         assertEquals(0, el.siblingElements().size());