fix duplicate head tag issue sveltejs#6463

Author: hbirler

src/compiler/compile/render_dom/wrappers/Head.ts

@@ -36,7 +36,7 @@ export default class HeadWrapper extends Wrapper {
 		let nodes;
 		if (this.renderer.options.hydratable && this.fragment.nodes.length) {
 			nodes = block.get_unique_name('head_nodes');
-			block.chunks.claim.push(b`const ${nodes} = @query_selector_all('[data-svelte="${this.node.id}"]', @_document.head);`);
+			block.chunks.claim.push(b`const ${nodes} = @head_selector('${this.node.id}', @_document.head);`);
 		}
 
 		this.fragment.render(block, x`@_document.head` as unknown as Identifier, nodes);

src/runtime/internal/dom.ts

@@ -630,6 +630,25 @@ export function query_selector_all(selector: string, parent: HTMLElement = docum
 	return Array.from(parent.querySelectorAll(selector)) as ChildNodeArray;
 }
 
+export function head_selector(nodeId: string, head: HTMLElement) {
+	const result = [];
+	let started = 0;
+	for (const node of head.childNodes) {
+		if (node.nodeType === 8 /* comment node */ && node.textContent.trim() === 'HTML_TAG_END') {
+			started -= 1;
+			result.push(node);
+		} else if (node.nodeType === 8 /* comment node */ && node.textContent.trim() === 'HTML_TAG_START') {
+			started += 1;
+			result.push(node);
+		} else if (started > 0) {
+			result.push(node);
+		} else if (node.nodeType === 1 /* element node */ && (<Element>node).getAttribute('data-svelte') === nodeId) {
+			result.push(node);
+		}
+	}
+	return result;
+}
+
 export class HtmlTag {
 	// parent for creating node
 	e: HTMLElement;