feat: parse :is and :where as nested-pseudo-classes

Author: barak007

lib/parse.js

@@ -178,7 +178,7 @@ function getSelectors() {
 	selectors[uniRegexp.typeMatchClass] = typeMatch("class");
 	selectors[uniRegexp.typeMatchId] = typeMatch("id");
 	var selectorsSecondHalf = {
-		":(not|matches|has|local|global)\\((\\s*)": nestedPseudoClassStartMatch,
+		":(not|matches|is|where|has|local|global)\\((\\s*)": nestedPseudoClassStartMatch,
 		":((?:\\\\.|[A-Za-z_\\-0-9])+)\\(": pseudoClassStartMatch,
 		":((?:\\\\.|[A-Za-z_\\-0-9])+)": typeMatch("pseudo-class"),
 		"::((?:\\\\.|[A-Za-z_\\-0-9])+)": typeMatch("pseudo-element"),

test/test-cases.js

@@ -361,7 +361,50 @@ module.exports = {
 			] }
 		])
 	],
-
+  "nested pseudo class with multiple selectors (:is)": [
+    ":is( h1, h2 )",
+    singleSelector([
+    {
+        type: "nested-pseudo-class",
+        name: "is",
+        nodes: [
+        {
+            type: "selector",
+            nodes: [{ type: "element", name: "h1" }],
+            before: " ",
+        },
+        {
+            type: "selector",
+            nodes: [{ type: "element", name: "h2" }],
+            before: " ",
+            after: " ",
+        },
+        ],
+    },
+    ]),
+  ],
+  "nested pseudo class with multiple selectors (:where)": [
+      ":where( h1, h2 )",
+      singleSelector([
+      {
+          type: "nested-pseudo-class",
+          name: "where",
+          nodes: [
+          {
+              type: "selector",
+              nodes: [{ type: "element", name: "h1" }],
+              before: " ",
+          },
+          {
+              type: "selector",
+              nodes: [{ type: "element", name: "h2" }],
+              before: " ",
+              after: " ",
+          },
+          ],
+      },
+      ]),
+  ],
 	"available nested pseudo classes": [
 		":not(:active):matches(:focus)",
 		singleSelector([