From 7a37f27c0040ea32cd79068bbd07e95ad866285c Mon Sep 17 00:00:00 2001
From: Florian Lefebvre <contact@florian-lefebvre.dev>
Date: Wed, 16 Apr 2025 10:30:27 +0200
Subject: [PATCH] fix(fonts): tech(undefined) for local provider

---
 .changeset/few-flowers-notice.md                     |  5 +++++
 packages/astro/src/assets/fonts/utils.ts             |  7 ++++---
 packages/astro/test/units/assets/fonts/utils.test.js | 10 ++++++++++
 3 files changed, 19 insertions(+), 3 deletions(-)
 create mode 100644 .changeset/few-flowers-notice.md

diff --git a/.changeset/few-flowers-notice.md b/.changeset/few-flowers-notice.md
new file mode 100644
index 000000000000..f6221bb00587
--- /dev/null
+++ b/.changeset/few-flowers-notice.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes a case where fonts using a local provider would not work because of an invalid generated `src` 
diff --git a/packages/astro/src/assets/fonts/utils.ts b/packages/astro/src/assets/fonts/utils.ts
index 2d8c8ef2225c..5101d6661093 100644
--- a/packages/astro/src/assets/fonts/utils.ts
+++ b/packages/astro/src/assets/fonts/utils.ts
@@ -36,14 +36,15 @@ export function generateFontFace(family: string, font: unifont.FontFaceData) {
 }
 
 // Source: https://github.com/nuxt/fonts/blob/main/src/css/render.ts#L68-L81
-function renderFontSrc(sources: Exclude<unifont.FontFaceData['src'][number], string>[]) {
+export function renderFontSrc(sources: Exclude<unifont.FontFaceData['src'][number], string>[]) {
 	return sources
 		.map((src) => {
 			if ('url' in src) {
 				let rendered = `url("${src.url}")`;
 				for (const key of ['format', 'tech'] as const) {
-					if (key in src) {
-						rendered += ` ${key}(${src[key]})`;
+					const value = src[key]
+					if (value) {
+						rendered += ` ${key}(${value})`;
 					}
 				}
 				return rendered;
diff --git a/packages/astro/test/units/assets/fonts/utils.test.js b/packages/astro/test/units/assets/fonts/utils.test.js
index 68dc95e2954f..ef106499ea41 100644
--- a/packages/astro/test/units/assets/fonts/utils.test.js
+++ b/packages/astro/test/units/assets/fonts/utils.test.js
@@ -10,6 +10,7 @@ import {
 	isFontType,
 	isGenericFontFamily,
 	proxyURL,
+	renderFontSrc,
 	resolveFontFamily,
 } from '../../../../dist/assets/fonts/utils.js';
 
@@ -537,4 +538,13 @@ describe('fonts utils', () => {
 			]);
 		});
 	});
+
+	describe('renderFontSrc()', () => {
+		it('does not output tech(undefined) if key is present without value', () => {
+			assert.equal(
+				renderFontSrc([{ url: 'test', tech: undefined }]).includes('tech(undefined)'),
+				false,
+			);
+		});
+	});
 });