rehypeHeadingIds() — astro Function Reference

Source Code

packages/markdown/remark/src/rehype-collect-headings.ts lines 17–74

export function rehypeHeadingIds(): ReturnType<RehypePlugin> {
	return function (tree, file) {
		const headings: MarkdownHeading[] = [];
		const frontmatter = file.data.astro?.frontmatter;
		const slugger = new Slugger();
		const isMDX = isMDXFile(file);
		visit(tree, (node) => {
			if (node.type !== 'element') return;
			const { tagName } = node;
			if (tagName[0] !== 'h') return;
			const [, level] = /h([0-6])/.exec(tagName) ?? [];
			if (!level) return;
			const depth = Number.parseInt(level);

			let text = '';
			visit(node, (child, __, parent) => {
				if (child.type === 'element' || parent == null) {
					return;
				}
				if (child.type === 'raw') {
					if (/^\n?<.*>\n?$/.test(child.value)) {
						return;
					}
				}
				if (rawNodeTypes.has(child.type)) {
					if (isMDX || codeTagNames.has(parent.tagName)) {
						let value = child.value;
						if (isMdxTextExpression(child) && frontmatter) {
							const frontmatterPath = getMdxFrontmatterVariablePath(child);
							if (Array.isArray(frontmatterPath) && frontmatterPath.length > 0) {
								const frontmatterValue = getMdxFrontmatterVariableValue(
									frontmatter,
									frontmatterPath,
								);
								if (typeof frontmatterValue === 'string') {
									value = frontmatterValue;
								}
							}
						}
						text += value;
					} else {
						text += child.value.replace(/\{/g, '${');
					}
				}
			});

			node.properties = node.properties || {};
			if (typeof node.properties.id !== 'string') {
				node.properties.id = slugger.slug(text);
			}

			headings.push({ depth, slug: node.properties.id, text });
		});

		file.data.astro ??= {};
		file.data.astro.headings = headings;
	};
}