fix: set default charset for Astro pages in dev

packages/astro/src/vite-plugin-astro-server/index.ts

@@ -326,6 +326,9 @@ async function handleRequest(
 			}
 		} else {
 			const result = await ssr(preloadedComponent, options);
+			if (!result.headers.has('Content-Type')) {
+				result.headers.set('Content-Type', 'text/html;charset=utf-8');
+			}
 			return await writeSSRResult(result, res);
 		}
 	} catch (_err) {

packages/astro/test/astro-pages.test.js

@@ -42,5 +42,11 @@ describe('Pages', () => {
 
 			expect($('#testing').length).to.be.greaterThan(0);
 		});
+
+		it('Has default Content-Type with charset=utf-8', async () => {
+			const html = await fixture.fetch('/');
+
+			expect(html.headers.get('Content-Type')).to.equal('text/html;charset=utf-8');
+		});
 	});
 });