ImmediateParent evaluator should not match the context root

Fixes #2018

Was a regression when ImmediateParent was reimplemented into ImmediateParentRun

CHANGES

@@ -12,6 +12,10 @@ Release 1.17.1 [PENDING]
     be emitted as CDATA nodes, so that they can be parsed correctly by an XML parser.
     <https://github.com/jhy/jsoup/pull/1720>
 
+  * Bugfix: the Immediate Parent selector `>` could match elements above the root context element, causing incorrect
+    elements to be returned when used on elements other than the root document.
+    <https://github.com/jhy/jsoup/issues/2018>
+
 Release 1.16.2 [20-Oct-2023]
   * Improvement: optimized the performance of complex CSS selectors, by adding a cost-based query planner. Evaluators
     are sorted by their relative execution cost, and executed in order of lower to higher cost. This speeds the

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

@@ -189,7 +189,9 @@ void add(Evaluator evaluator) {
 
         @Override
         public boolean matches(Element root, Element element) {
-            // evaluate from last to first
+            if (element == root)
+                return false; // cannot match as the second eval (first parent test) would be above the root
+
             for (int i = evaluators.size() -1; i >= 0; --i) {
                 if (element == null)
                     return false;

src/test/java/org/jsoup/select/SelectorTest.java

@@ -1181,4 +1181,29 @@ public void wildcardNamespaceMatchesNoNamespace() {
         assertEquals("4", notEmpty.get(0).id());
         assertEquals("5", notEmpty.get(1).id());
     }
+
+    @Test public void parentFromSpecifiedDescender() {
+        // https://github.com/jhy/jsoup/issues/2018
+        String html = "<ul id=outer><li>Foo</li><li>Bar <ul id=inner><li>Baz</li><li>Qux</li></ul> </li></ul>";
+        Document doc = Jsoup.parse(html);
+
+        Element ul = doc.expectFirst("#outer");
+        assertEquals(2, ul.childrenSize());
+
+        Element li1 = ul.expectFirst("> li:nth-child(1)");
+        assertEquals("Foo", li1.ownText());
+        assertTrue(li1.select("ul").isEmpty());
+
+        Element li2 = ul.expectFirst("> li:nth-child(2)");
+        assertEquals("Bar", li2.ownText());
+
+        // And now for the bug - li2 select was not restricted to the li2 context
+        Elements innerLis = li2.select("ul > li");
+        assertEquals(2, innerLis.size());
+        assertEquals("Baz", innerLis.first().ownText());
+
+        // Confirm that parent selector (" ") works same as immediate parent (">");
+        Elements innerLisFromParent = li2.select("ul li");
+        assertEquals(innerLis, innerLisFromParent);
+    }
 }