Wrong behavior of local font's `font-family` handling in Turbopack

[shuding]

The logic to allow specifying custom font-family of a local font implemented in #76274 is for Webpack only, and not ported to Turbopack.

Webpack

font-family: variableName is only inserted when there's no custom font family set:

next.js/packages/font/src/local/loader.ts

Line 67 in db55283

...(hasCustomFontFamily ? [] : [['font-family', variableName]]),

Turbopack

scoped_font_family is always inserted:

next.js/crates/next-core/src/next_font/local/stylesheet.rs

Lines 67 to 82 in db55283

	@font-face {{
	{}
	font-family: '{}';
	src: url('@vercel/turbopack-next/internal/font/local/font?{}') format('{}');
	font-display: {};
	{}{}
	}}
	"#,
	options.declarations.as_ref().map_or_else(
	|| "".to_owned(),
	|declarations| declarations
	.iter()
	.map(|declaration| format!("{}: {};", declaration.prop, declaration.value))
	.join("\n")
	),
	scoped_font_family,

Reproduction

import localFont from 'next/font/local'

const geist = localFont({
  src: './geist.woff2',
  declarations: [
    {
      prop: 'font-family',
      value: "Geist",
    },
  ],
})

With Turbopack, the above code results in a @font-face with two font-family properties:

[github-actions]

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[github-actions]

This closed issue has been automatically locked because it had no new activity for 2 weeks. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.