@astrojs/mdx/dist/rehype-apply-frontmatter-export.js

Add support for MDX pages in your Astro site

import path from "node:path";
import { fileURLToPath } from "node:url";
import { isFrontmatterValid } from "@astrojs/markdown-remark";
import { jsToTreeNode } from "./utils.js";
const exportConstPartialTrueRe = /export\s+const\s+partial\s*=\s*true/;
function rehypeApplyFrontmatterExport() {
  return function(tree, 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 = [
      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);
  };
}
function shouldAddCharset(tree, vfile) {
  const srcDirUrl = vfile.data.applyFrontmatterExport?.srcDir;
  if (!srcDirUrl) return false;
  const hasConstPartialTrue = tree.children.some(
    (node) => node.type === "mdxjsEsm" && exportConstPartialTrueRe.test(node.value)
  );
  if (hasConstPartialTrue) return false;
  const pagesDir = path.join(fileURLToPath(srcDirUrl), "pages").replace(/\\/g, "/");
  const filePath = vfile.path;
  if (!filePath.startsWith(pagesDir)) return false;
  const hasLeadingUnderscoreInPath = filePath.slice(pagesDir.length).replace(/\\/g, "/").split("/").some((part) => part.startsWith("_"));
  if (hasLeadingUnderscoreInPath) return false;
  for (const child of tree.children) {
    if (child.type === "element") break;
    if (child.type === "mdxJsxFlowElement") {
      if (child.name == null) break;
      if (child.name[0] === child.name[0].toLowerCase()) break;
      return false;
    }
  }
  return true;
}
export {
  rehypeApplyFrontmatterExport
};