From 48161b77caf35a9f3c285c0c7fbb9d8a937241c9 Mon Sep 17 00:00:00 2001
From: Don Denton <don@happycollision.com>
Date: Tue, 14 Jun 2022 16:20:13 -0400
Subject: [PATCH] Fix unintentional missing type data in `MarkdownInstance`
 (#3397)

* Update MarkdownInstance type

The return of the `default` function includes the same `frontmatter`
data as the parent object, merged with the `astro` data. The inclusion
of that frontmatter type was previously not recognized by TS, and fell
back to a `Record<string, any>`. This change persists the more accurate
type, as the runtime code does.

* fixup! Update MarkdownInstance type

(This change is what I'd personally do, but I don't really know how you
expect people to use `MarkdownContent` in practice, or if there is some
deeper benefit you wish to exploit by leaving it as an interface instead
of a type.
---
 .changeset/eleven-planes-deliver.md | 5 +++++
 packages/astro/src/@types/astro.ts  | 7 +++----
 2 files changed, 8 insertions(+), 4 deletions(-)
 create mode 100644 .changeset/eleven-planes-deliver.md

diff --git a/.changeset/eleven-planes-deliver.md b/.changeset/eleven-planes-deliver.md
new file mode 100644
index 000000000..c3d44b459
--- /dev/null
+++ b/.changeset/eleven-planes-deliver.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+MarkdownInstance: Persist frontmatter type into the return of `.default()`
diff --git a/packages/astro/src/@types/astro.ts b/packages/astro/src/@types/astro.ts
index 137fb3b85..7dd341d6f 100644
--- a/packages/astro/src/@types/astro.ts
+++ b/packages/astro/src/@types/astro.ts
@@ -760,7 +760,7 @@ export interface MarkdownInstance<T extends Record<string, any>> {
 	getHeaders(): Promise<MarkdownHeader[]>;
 	default: () => Promise<{
 		metadata: MarkdownMetadata;
-		frontmatter: MarkdownContent;
+		frontmatter: MarkdownContent<T>;
 		$$metadata: Metadata;
 		default: AstroComponentFactory;
 	}>;
@@ -817,10 +817,9 @@ export interface MarkdownParserResponse extends MarkdownRenderingResult {
  * The `content` prop given to a Layout
  * https://docs.astro.build/guides/markdown-content/#markdown-layouts
  */
-export interface MarkdownContent {
-	[key: string]: any;
+export type MarkdownContent<T extends Record<string, any> = Record<string, any>> = T & {
 	astro: MarkdownMetadata;
-}
+};
 
 /**
  * paginate() Options