fix: do not mark invalid/non-primitive fontFamily tokens as fontFamily (#32)

Author: bartveneman

src/destructure-font-family.test.ts

@@ -21,18 +21,18 @@ test('multiple font-family with spaces and quotes', () => {
 	expect.soft(destructure_font_family('"Arial Black", sans-serif')).toEqual(['Arial Black', 'sans-serif'])
 })
 
+test('with emoji name', () => {
+	expect.soft(destructure_font_family('💪')).toEqual(['💪'])
+})
+
 test('single var()', () => {
-	expect.soft(destructure_font_family('var(--family)')).toEqual(['var(--family)'])
+	expect.soft(destructure_font_family('var(--family)')).toBeUndefined()
 })
 
 test('multiple var()', () => {
-	expect.soft(destructure_font_family('var(--family), var(--family2)')).toEqual(['var(--family)', 'var(--family2)'])
+	expect.soft(destructure_font_family('var(--family), var(--family2)')).toBeUndefined()
 })
 
 test('var() with fallback', () => {
-	expect.soft(destructure_font_family('var(--family, Arial)')).toEqual(['var(--family, Arial)'])
-})
-
-test('with emoji name', () => {
-	expect.soft(destructure_font_family('💪')).toEqual(['💪'])
+	expect.soft(destructure_font_family('var(--family, Arial)')).toBeUndefined()
 })

src/destructure-font-family.ts

@@ -1,10 +1,14 @@
 import { parse, type Value, type CssNode } from 'css-tree'
 import { unquote } from './unquote.js'
 
-export function destructure_font_family(value: string): string[] {
+export function destructure_font_family(value: string): string[] | undefined {
+	if (value.toLowerCase().includes('var(')) {
+		return undefined
+	}
+
 	let ast = parse(value, {
 		context: 'value',
-		positions: true
+		positions: true,
 	}) as Value
 
 	function generate(node: CssNode) {