fix: do not erroneously assume that the last node is a not selector

.changeset/spotty-cups-bow.md

@@ -0,0 +1,5 @@
+---
+"stylelint": patch
+---
+
+Fixed: `selector-not-notation` autofix for "simple" option

lib/rules/selector-not-notation/__tests__/index.js

@@ -68,6 +68,42 @@ testRule({
 			endLine: 1,
 			endColumn: 13,
 		},
+		{
+			code: ':not(.bar, .baz, .foo) {}',
+			fixed: ':not(.bar):not(.baz):not(.foo) {}',
+			message: messages.expected('simple'),
+			line: 1,
+			column: 1,
+			endLine: 1,
+			endColumn: 23,
+		},
+		{
+			code: ':not(.bar, .baz, .foo) .qux {}',
+			fixed: ':not(.bar):not(.baz):not(.foo) .qux {}',
+			message: messages.expected('simple'),
+			line: 1,
+			column: 1,
+			endLine: 1,
+			endColumn: 23,
+		},
+		{
+			code: ':not(.bar, .baz) .qux :not(.foo) {}',
+			fixed: ':not(.bar):not(.baz) .qux :not(.foo) {}',
+			message: messages.expected('simple'),
+			line: 1,
+			column: 1,
+			endLine: 1,
+			endColumn: 17,
+		},
+		{
+			code: ':not(.foo) .qux :not(.bar, .baz) {}',
+			fixed: ':not(.foo) .qux :not(.bar):not(.baz) {}',
+			message: messages.expected('simple'),
+			line: 1,
+			column: 17,
+			endLine: 1,
+			endColumn: 33,
+		},
 		{
 			code: ':not(a ,) {}',
 			fixed: ':not(a) {}',

lib/rules/selector-not-notation/index.js

@@ -130,6 +130,22 @@ const rule = (primary, _, context) => {
 	};
 };
 
+/**
+ * @param {Pseudo} not
+ * @returns {Node}
+ */
+const getLastConsecutiveNot = ({ parent, sourceIndex }) => {
+	assert(parent);
+
+	const nodes = parent.nodes;
+	const index = nodes.findIndex((node) => node.sourceIndex >= sourceIndex && !isNot(node));
+	const node = index === -1 ? nodes[nodes.length - 1] : nodes[index - 1];
+
+	assert(node);
+
+	return node;
+};
+
 /**
  * @param {Pseudo} not
  */
@@ -152,7 +168,7 @@ function fixSimple(not) {
 	not.nodes.push(firstSelector);
 
 	for (const s of simpleSelectors) {
-		const last = not.parent.last;
+		const last = getLastConsecutiveNot(not);
 
 		not.parent.insertAfter(last, last.clone({ nodes: [s] }));
 	}