fix: detect mdx files using full extension (#7192)

Author: ematipico

.changeset/lazy-zebras-invent.md

@@ -0,0 +1,6 @@
+---
+'@astrojs/mdx': patch
+'astro': patch
+---
+
+Detect `mdx` files using their full extension

packages/astro/src/content/runtime.ts

@@ -306,7 +306,7 @@ async function render({
 
 			let props = baseProps;
 			// Auto-apply MDX components export
-			if (id.endsWith('mdx')) {
+			if (id.endsWith('.mdx')) {
 				props = {
 					components: mod.components ?? {},
 					...baseProps,

packages/integrations/mdx/src/index.ts

@@ -94,7 +94,7 @@ export default function mdx(partialMdxOptions: Partial<MdxOptions> = {}): AstroI
 								// Override transform to alter code before MDX compilation
 								// ex. inject layouts
 								async transform(_, id) {
-									if (!id.endsWith('mdx')) return;
+									if (!id.endsWith('.mdx')) return;
 
 									// Read code from file manually to prevent Vite from parsing `import.meta.env` expressions
 									const { fileId } = getFileInfo(id, config);