use vfile to expose parsed frontMatter to all Remark plugins

packages/docusaurus-mdx-loader/package.json

@@ -43,6 +43,7 @@
     "unified": "^10.1.2",
     "unist-util-visit": "^2.0.3",
     "url-loader": "^4.1.1",
+    "vfile": "^5.3.7",
     "webpack": "^5.88.1"
   },
   "devDependencies": {

packages/docusaurus-mdx-loader/src/loader.ts

@@ -161,7 +161,11 @@ export async function mdxLoader(
 
   let result: {content: string; data: {[key: string]: unknown}};
   try {
-    result = await processor.process({content: preprocessedContent, filePath});
+    result = await processor.process({
+      content: preprocessedContent,
+      filePath,
+      frontMatter,
+    });
   } catch (errorUnknown) {
     const error = errorUnknown as Error;
 

packages/docusaurus-mdx-loader/src/processor.ts

@@ -36,9 +36,11 @@ type SimpleProcessor = {
   process: ({
     content,
     filePath,
+    frontMatter,
   }: {
     content: string;
     filePath: string;
+    frontMatter: {[key: string]: unknown};
   }) => Promise<SimpleProcessorResult>;
 };
 
@@ -83,6 +85,7 @@ async function createProcessorFactory() {
   // TODO using fork until PR merged: https://github.com/leebyron/remark-comment/pull/3
   const {default: comment} = await import('@slorber/remark-comment');
   const {default: directive} = await import('remark-directive');
+  const {VFile} = await import('vfile');
 
   // /!\ this method is synchronous on purpose
   // Using async code here can create cache entry race conditions!
@@ -164,16 +167,19 @@ async function createProcessorFactory() {
     });
 
     return {
-      process: async ({content, filePath}) =>
-        mdxProcessor
-          .process({
-            value: content,
-            path: filePath,
-          })
-          .then((vfile) => ({
-            content: vfile.toString(),
-            data: vfile.data,
-          })),
+      process: async ({content, filePath, frontMatter}) => {
+        const vfile = new VFile({
+          value: content,
+          path: filePath,
+          data: {
+            frontMatter,
+          },
+        });
+        return mdxProcessor.process(vfile).then((result) => ({
+          content: result.toString(),
+          data: result.data,
+        }));
+      },
     };
   }
 

yarn.lock

@@ -17237,7 +17237,7 @@ vfile@^4.0.0:
     unist-util-stringify-position "^2.0.0"
     vfile-message "^2.0.0"
 
-vfile@^5.0.0:
+vfile@^5.0.0, vfile@^5.3.7:
   version "5.3.7"
   resolved "https://registry.yarnpkg.com/vfile/-/vfile-5.3.7.tgz#de0677e6683e3380fafc46544cfe603118826ab7"
   integrity sha512-r7qlzkgErKjobAmyNIkkSpizsFPYiUPuJb5pNW1RB4JcYVZhs4lIbVqk8XPk033CV/1z8ss5pkax8SuhGpcG8g==