feat: support `layout` in MDX frontmatter (#4088)

* deps: add gray-matter

* feat: support layout frontmatter property

* test: frontmatter, content prop

* docs: update layout recommendation

* deps: fix lockfile

* chore: changeset

* fix: inherit rollup plugin transform

* fix: avoid parsing frontmatter on custom parsers

* fix: match YAML err handling from md

* docs: absolute url to docs

Co-authored-by: Sarah Rainsberger <sarah@rainsberger.ca>

* chore: formatting

Co-authored-by: Sarah Rainsberger <sarah@rainsberger.ca>

1 files changed, 22 insertions, 1 deletions

diff --git a/packages/integrations/mdx/src/utils.ts b/packages/integrations/mdx/src/utils.ts
index 6eb7a3570..97bc72d74 100644
--- a/packages/integrations/mdx/src/utils.ts
+++ b/packages/integrations/mdx/src/utils.ts
@@ -1,4 +1,5 @@
-import type { AstroConfig } from 'astro';
+import type { AstroConfig, SSRError } from 'astro';
+import matter from 'gray-matter';
 
 function appendForwardSlash(path: string) {
 	return path.endsWith('/') ? path : path + '/';
@@ -37,3 +38,23 @@ export function getFileInfo(id: string, config: AstroConfig): FileInfo {
 	}
 	return { fileId, fileUrl };
 }
+
+/**
+ * Match YAML exception handling from Astro core errors
+ * @see 'astro/src/core/errors.ts'
+ */ 
+export function getFrontmatter(code: string, id: string) {
+	try {
+		return matter(code).data;
+	} catch (e: any) {
+		if (e.name === 'YAMLException') {
+			const err: SSRError = e;
+			err.id = id;
+			err.loc = { file: e.id, line: e.mark.line + 1, column: e.mark.column };
+			err.message = e.reason;
+			throw err;
+		} else {
+			throw e;
+		}
+	}
+}