From 5dd22b875dc19a32c48692082fbd934e2b70da63 Mon Sep 17 00:00:00 2001
From: Chris Swithinbank <swithinbank@gmail.com>
Date: Fri, 1 Sep 2023 21:54:30 +0200
Subject: [PATCH] =?UTF-8?q?Throw=20error=20if=20a=20user=E2=80=99s=20proje?=
 =?UTF-8?q?ct=20adds=20MDX=20or=20sitemap=20integrations=20(#626)?=
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---
 .changeset/brown-olives-share.md |  5 +++++
 packages/starlight/index.ts      | 13 +++++++++++++
 2 files changed, 18 insertions(+)
 create mode 100644 .changeset/brown-olives-share.md

diff --git a/.changeset/brown-olives-share.md b/.changeset/brown-olives-share.md
new file mode 100644
index 0000000000..cd82595449
--- /dev/null
+++ b/.changeset/brown-olives-share.md
@@ -0,0 +1,5 @@
+---
+'@astrojs/starlight': minor
+---
+
+Throw an error for duplicate MDX or sitemap integrations
diff --git a/packages/starlight/index.ts b/packages/starlight/index.ts
index 4e7cba3dbd..2198f13fc1 100644
--- a/packages/starlight/index.ts
+++ b/packages/starlight/index.ts
@@ -50,6 +50,19 @@ export default function StarlightIntegration(opts: StarlightUserConfig): AstroIn
 				updateConfig(newConfig);
 			},
 
+			'astro:config:done': ({ config }) => {
+				const integrations = config.integrations.map(({ name }) => name);
+				for (const builtin of ['@astrojs/mdx', '@astrojs/sitemap']) {
+					if (integrations.filter((name) => name === builtin).length > 1) {
+						throw new Error(
+							`Found more than one instance of ${builtin}.\n` +
+								`Starlight includes ${builtin} by default.\n` +
+								'Please remove it from your integrations array in astro.config.mjs'
+						);
+					}
+				}
+			},
+
 			'astro:build:done': ({ dir }) => {
 				const targetDir = fileURLToPath(dir);
 				const cwd = dirname(fileURLToPath(import.meta.url));