rehypeApplyFrontmatterExport() — astro Function Reference

Architecture documentation for the rehypeApplyFrontmatterExport() function in rehype-apply-frontmatter-export.ts from the astro codebase.

Function typescript CoreAstro RoutingSystem calls 1

Entity Profile

CoreAstro→ RoutingSystem→ rehypeApplyFrontmatterExport() — astro Function Reference

Dependency Diagram

graph TD
  3cb2c0d6_fe6a_7406_95ac_85f24f55edc1["rehypeApplyFrontmatterExport()"]
  50f0dfd4_d9b5_8cd5_80a6_3519a94ab6d7["rehype-apply-frontmatter-export.ts"]
  3cb2c0d6_fe6a_7406_95ac_85f24f55edc1 -->|defined in| 50f0dfd4_d9b5_8cd5_80a6_3519a94ab6d7
  e5738373_9d28_407c_3733_9fa1b3abbc0b["shouldAddCharset()"]
  3cb2c0d6_fe6a_7406_95ac_85f24f55edc1 -->|calls| e5738373_9d28_407c_3733_9fa1b3abbc0b
  style 3cb2c0d6_fe6a_7406_95ac_85f24f55edc1 fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

packages/integrations/mdx/src/rehype-apply-frontmatter-export.ts lines 19–72

export function rehypeApplyFrontmatterExport() {
	return function (tree: Root, vfile: VFile) {
		const frontmatter = vfile.data.astro?.frontmatter;
		if (!frontmatter || !isFrontmatterValid(frontmatter))
			throw new Error(
				// Copied from Astro core `errors-data`
				// TODO: find way to import error data from core
				'[MDX] A remark or rehype plugin attempted to inject invalid frontmatter. Ensure "astro.frontmatter" is set to a valid JSON object that is not `null` or `undefined`.',
			);
		const extraChildren: RootContent[] = [
			jsToTreeNode(`export const frontmatter = ${JSON.stringify(frontmatter)};`),
		];
		if (frontmatter.layout) {
			extraChildren.unshift(
				jsToTreeNode(
					// NOTE: Use `__astro_*` import names to prevent conflicts with user code
					/** @see 'vite-plugin-markdown' for layout props reference */
					`\
import { jsx as __astro_layout_jsx__ } from 'astro/jsx-runtime';
import __astro_layout_component__ from ${JSON.stringify(frontmatter.layout)};

export default function ({ children }) {
	const { layout, ...content } = frontmatter;
	content.file = file;
	content.url = url;
	return __astro_layout_jsx__(__astro_layout_component__, {
		file,
		url,
		content,
		frontmatter: content,
		headings: getHeadings(),
		'server:root': true,
		children,
	});
};`,
				),
			);
		} else if (shouldAddCharset(tree, vfile)) {
			extraChildren.unshift({
				type: 'mdxJsxFlowElement',
				name: 'meta',
				attributes: [
					{
						type: 'mdxJsxAttribute',
						name: 'charset',
						value: 'utf-8',
					},
				],
				children: [],
			});
		}
		tree.children = extraChildren.concat(tree.children);
	};
}