Fix <link> tag not being self-closing (#3506)

* fix(#392): ensure link tags are rendered as void elements

* test: ensure html does not include a `</link>` end tag

* chore: add changeset

.changeset/new-knives-raise.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fix issue where generated `link` tags would have an invalid closing tag

packages/astro/src/runtime/server/index.ts

@@ -715,5 +715,8 @@ function renderElement(
 			children = defineScriptVars(defineVars) + '\n' + children;
 		}
 	}
+	if ((children == null || children == '') && voidElementNames.test(name)) {
+		return `<${name}${internalSpreadAttributes(props, shouldEscape)} />`;
+	}
 	return `<${name}${internalSpreadAttributes(props, shouldEscape)}>${children}</${name}>`;
 }

packages/astro/test/0-css.test.js

@@ -18,14 +18,15 @@ describe('CSS', function () {
 	// test HTML and CSS contents for accuracy
 	describe('build', () => {
 		let $;
+		let html;
 		let bundledCSS;
 
 		before(async () => {
 			this.timeout(45000); // test needs a little more time in CI
 			await fixture.build();
 
 			// get bundled CSS (will be hashed, hence DOM query)
-			const html = await fixture.readFile('/index.html');
+			html = await fixture.readFile('/index.html');
 			$ = cheerio.load(html);
 			const bundledCSSHREF = $('link[rel=stylesheet][href^=/assets/]').attr('href');
 			bundledCSS = (await fixture.readFile(bundledCSSHREF.replace(/^\/?/, '/')))
@@ -49,6 +50,10 @@ describe('CSS', function () {
 				expect(bundledCSS).to.include(expected);
 			});
 
+			it('Generated link tags are void elements', async () => {
+				expect(html).to.not.include("</link>");
+			});
+
 			it('No <style> skips scoping', async () => {
 				// Astro component without <style> should not include scoped class
 				expect($('#no-scope').attr('class')).to.equal(undefined);