is_tag_valid_with_ancestor() — svelte Function Reference

Source Code

packages/svelte/src/html-tree-validation.js lines 144–173

export function is_tag_valid_with_ancestor(child_tag, ancestors, child_loc, ancestor_loc) {
	if (child_tag.includes('-')) return null; // custom elements can be anything

	const ancestor_tag = ancestors[ancestors.length - 1];
	const disallowed = disallowed_children[ancestor_tag];
	if (!disallowed) return null;

	if ('reset_by' in disallowed && disallowed.reset_by) {
		for (let i = ancestors.length - 2; i >= 0; i--) {
			const ancestor = ancestors[i];
			if (ancestor.includes('-')) return null; // custom elements can be anything

			// A reset means that forbidden descendants are allowed again
			if (disallowed.reset_by.includes(ancestors[i])) {
				return null;
			}
		}
	}

	if ('descendant' in disallowed && disallowed.descendant.includes(child_tag)) {
		const child = child_loc ? `\`<${child_tag}>\` (${child_loc})` : `\`<${child_tag}>\``;
		const ancestor = ancestor_loc
			? `\`<${ancestor_tag}>\` (${ancestor_loc})`
			: `\`<${ancestor_tag}>\``;

		return `${child} cannot be a descendant of ${ancestor}`;
	}

	return null;
}