Add support for Next.js app router exports (#34)

* Add support for Next.js `metadata` export

* Support all Next.js exports under `nextjs` key

* Limit to `metadata` and `revalidate` exports

Co-authored-by: Mike Fix <[email protected]>

* Use implicit return

Co-authored-by: Mike Fix <[email protected]>

---------

Co-authored-by: Mike Fix <[email protected]>

Author: bradlc

src/loader.js

@@ -119,6 +119,15 @@ async function load(source) {
   }
 
   this.addContextDependency(schemaDir);
+
+  const nextjsExports = [
+    'metadata',
+    'revalidate',
+  ]
+  const nextjsExportsCode = nextjsExports
+    .map((name) => `export const ${name} = frontmatter.nextjs?.${name};`)
+    .join('\n')
+
   const result = `import React from 'react';
 import yaml from 'js-yaml';
 // renderers is imported separately so Markdoc isn't sent to the client
@@ -206,7 +215,7 @@ ${
   };
 }`
 }
-
+${appDir ? nextjsExportsCode : ''}
 export default${appDir ? ' async' : ''} function MarkdocComponent(props) {
   const markdoc = ${appDir ? 'await getMarkdocData()' : 'props.markdoc'};
   // Only execute HMR code in development

tests/__snapshots__/index.test.js.snap

@@ -169,7 +169,14 @@ async function getMarkdocData(context = {}) {
 }
 
 
-
+export const dynamic = frontmatter.nextjs?.dynamic;
+export const dynamicParams = frontmatter.nextjs?.dynamicParams;
+export const fetchCache = frontmatter.nextjs?.fetchCache;
+export const maxDuration = frontmatter.nextjs?.maxDuration;
+export const metadata = frontmatter.nextjs?.metadata;
+export const preferredRegion = frontmatter.nextjs?.preferredRegion;
+export const revalidate = frontmatter.nextjs?.revalidate;
+export const runtime = frontmatter.nextjs?.runtime;
 export default async function MarkdocComponent(props) {
   const markdoc = await getMarkdocData();
   // Only execute HMR code in development

tests/index.test.js

@@ -177,6 +177,15 @@ test('app router', async () => {
   );
 });
 
+test('app router metadata', async () => {
+  const output = await callLoader(
+    options({ appDir: true }),
+    source.replace('---', '---\nmetadata:\n  title: Metadata title')
+  );
+
+  expect(output).toContain('export const metadata = frontmatter.nextjs?.metadata;')
+});
+
 test.each([
   [undefined, undefined],
   ['./schemas/folders', 'markdoc1'],