[html] fix TypeError in nth-child query selector (#2015)

Author: sstasi95

pkgs/html/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.15.6-wip
+
+- Fixed a TypeError in nth-child with non numeric value (e.g. `nth-child(even)`)
+
 ## 0.15.5+1
 
 - Support "ambiguous ampersand" in attribute values.

pkgs/html/lib/src/query_selector.dart

@@ -218,10 +218,17 @@ class SelectorEvaluator extends Visitor {
         final exprs = node.expression.expressions;
         if (exprs.length == 1 && exprs[0] is LiteralTerm) {
           final literal = exprs[0] as LiteralTerm;
+
+          if (literal.value is! num) {
+            // non numeric values (e.g. `nth-child(even)`) are not supported
+            return false;
+          }
+
+          final numericLiteral = literal.value as num;
           final parent = _element!.parentNode;
           return parent != null &&
-              (literal.value as num) > 0 &&
-              parent.nodes.indexOf(_element) == literal.value;
+              numericLiteral > 0 &&
+              parent.nodes.indexOf(_element) == numericLiteral;
         }
         break;
 

pkgs/html/pubspec.yaml

@@ -1,5 +1,5 @@
 name: html
-version: 0.15.5+1
+version: 0.15.6-wip
 description: APIs for parsing and manipulating HTML content outside the browser.
 repository: https://github.com/dart-lang/tools/tree/main/pkgs/html
 issue_tracker: https://github.com/dart-lang/tools/issues?q=is%3Aissue+is%3Aopen+label%3Apackage%3Ahtml