Improve YAML error handling (#3557)

* chore: improve YAML errors

* chore: add changeset

3 files changed, 31 insertions, 2 deletions

diff --git a/.changeset/rare-buckets-kneel.md b/.changeset/rare-buckets-kneel.md
new file mode 100644
index 000000000..74a05f545
--- /dev/null
+++ b/.changeset/rare-buckets-kneel.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Improve the way YAML errors are surfaced
diff --git a/packages/astro/src/core/errors.ts b/packages/astro/src/core/errors.ts
index e295d9191..fa80414e1 100644
--- a/packages/astro/src/core/errors.ts
+++ b/packages/astro/src/core/errors.ts
@@ -69,6 +69,20 @@ export function collectErrorMetadata(e: any): ErrorWithMetadata {
 		(e as any).stack = eol.lf((e as any).stack);
 	}
 
+
+	if (e.name === 'YAMLException') {
+		const err = e as SSRError;
+		err.loc = { file: (e as any).id, line: (e as any).mark.line, column: (e as any).mark.column }
+		err.message = (e as any).reason;
+		
+		if (!err.frame) {
+			try {
+				const fileContents = fs.readFileSync(err.loc.file!, 'utf8');
+				err.frame = codeFrame(fileContents, err.loc);
+			} catch {}
+		}
+	}
+
 	// Astro error (thrown by esbuild so it needs to be formatted for Vite)
 	if (Array.isArray((e as any).errors)) {
 		const { location, pluginName, text } = (e as BuildResult).errors[0];
diff --git a/packages/astro/src/vite-plugin-markdown/index.ts b/packages/astro/src/vite-plugin-markdown/index.ts
index 1a0b9f228..90b25625f 100644
--- a/packages/astro/src/vite-plugin-markdown/index.ts
+++ b/packages/astro/src/vite-plugin-markdown/index.ts
@@ -10,6 +10,7 @@ import type { AstroConfig } from '../@types/astro';
 import { pagesVirtualModuleId } from '../core/app/index.js';
 import { prependForwardSlash } from '../core/path.js';
 import { resolvePages, viteID } from '../core/util.js';
+import { collectErrorMetadata } from '../core/errors.js';
 import { PAGE_SSR_SCRIPT_ID } from '../vite-plugin-scripts/index.js';
 import { getFileInfo } from '../vite-plugin-utils/index.js';
 
@@ -20,6 +21,15 @@ interface AstroPluginOptions {
 const MARKDOWN_IMPORT_FLAG = '?mdImport';
 const MARKDOWN_CONTENT_FLAG = '?content';
 
+function safeMatter(source: string, id: string) {
+	try {
+		return matter(source);
+	} catch (e) {
+		(e as any).id = id;
+		throw collectErrorMetadata(e)
+	}
+}
+
 // TODO: Clean up some of the shared logic between this Markdown plugin and the Astro plugin.
 // Both end up connecting a `load()` hook to the Astro compiler, and share some copy-paste
 // logic in how that is done.
@@ -82,7 +92,7 @@ export default function markdown({ config }: AstroPluginOptions): Plugin {
 				const { fileId, fileUrl } = getFileInfo(id, config);
 
 				const source = await fs.promises.readFile(fileId, 'utf8');
-				const { data: frontmatter, content: rawContent } = matter(source);
+				const { data: frontmatter, content: rawContent } = safeMatter(source, fileId);
 				return {
 					code: `
 						// Static
@@ -127,7 +137,7 @@ export default function markdown({ config }: AstroPluginOptions): Plugin {
 				const hasInjectedScript = isPage && config._ctx.scripts.some((s) => s.stage === 'page-ssr');
 
 				// Extract special frontmatter keys
-				let { data: frontmatter, content: markdownContent } = matter(source);
+				let { data: frontmatter, content: markdownContent } = safeMatter(source, filename);
 
 				// Turn HTML comments into JS comments while preventing nested `*/` sequences
 				// from ending the JS comment by injecting a zero-width space