feat: add markdown output plugin to copy markdown files alongside HTML (#882)

* feat: add markdown output plugin to copy markdown files alongside HTML

* Remove async, simplify

Author: clavin

docusaurus.config.ts

@@ -242,6 +242,7 @@ const config: Config = {
     path.resolve(__dirname, './src/plugins/releases/index.ts'),
     path.resolve(__dirname, './src/plugins/fiddle/index.ts'),
     path.resolve(__dirname, './src/plugins/governance/index.ts'),
+    path.resolve(__dirname, './src/plugins/markdown-output/index.ts'),
   ],
   presets: [
     [

src/plugins/markdown-output/index.ts

@@ -0,0 +1,83 @@
+/**
+ * Plugin to output index.md files alongside index.html in the build directory.
+ * This copies the original markdown source files to their corresponding locations
+ * in the build output.
+ */
+
+import fs from 'node:fs';
+import path from 'node:path';
+import { Plugin } from '@docusaurus/types';
+import logger from '@docusaurus/logger';
+
+/** Route prefixes to copy markdown files within. */
+const PREFIXES = ['docs/', 'blog/'];
+
+type Context = Parameters<Plugin['postBuild']>[0];
+
+function findMarkdownSource(
+  routePath: string,
+  { siteDir }: Context,
+): string | null {
+  for (const prefix of PREFIXES) {
+    const routePrefix = `/${prefix}`;
+
+    if (!routePath.startsWith(routePrefix)) continue;
+
+    // Since routePrefix is absolute and routePath starts with routePrefix, it too must be absolute
+    // meaning we can safely use path.relative to get the relative path
+    const relativePath = path.relative(routePrefix, routePath);
+    const sourceDir = path.join(siteDir, prefix);
+
+    // Try direct file path first (e.g., /docs/tutorial/intro.md)
+    const directPath = path.join(sourceDir, `${relativePath}.md`);
+    if (fs.existsSync(directPath)) return directPath;
+
+    // Try index.md in directory (e.g., /docs/tutorial/intro/index.md)
+    const indexPath = path.join(sourceDir, relativePath, 'index.md');
+    if (fs.existsSync(indexPath)) return indexPath;
+  }
+
+  return null;
+}
+
+function copyMarkdownForRoute(routePath: string, context: Context): boolean {
+  const { outDir } = context;
+
+  // Find corresponding markdown source
+  const mdSourcePath = findMarkdownSource(routePath, context);
+  if (!mdSourcePath) return false;
+
+  // Check if HTML output exists
+  const htmlPath = path.join(outDir, routePath, 'index.html');
+  if (!fs.existsSync(htmlPath)) return false;
+
+  // Copy markdown to output directory
+  const outputMdPath = path.join(outDir, routePath, 'index.md');
+  fs.copyFileSync(mdSourcePath, outputMdPath);
+
+  return true;
+}
+
+export default function markdownOutputPlugin(): Plugin {
+  return {
+    name: 'markdown-output-plugin',
+    postBuild(context) {
+      logger.info('Copying markdown files to build directory...');
+
+      // Filter to only routes in target prefixes
+      const routes = context.routesPaths.filter((routePath) =>
+        PREFIXES.some((prefix) => routePath.startsWith(`/${prefix}`)),
+      );
+
+      // Process all routes
+      let copiedCount = 0;
+      for (const routePath of routes) {
+        if (copyMarkdownForRoute(routePath, context)) {
+          copiedCount += 1;
+        }
+      }
+
+      logger.success(`Copied ${copiedCount} markdown files to build directory`);
+    },
+  };
+}