Function pickVariableIndexCSS

packages/core/src/css/planner.ts:35–53

(
	variable: FontConfig['variable'],
	facesByCSSFile: ReadonlyMap<string, readonly FontFace[]>,
)

};

const pickVariableIndexCSS = (
	variable: FontConfig['variable'],
	facesByCSSFile: ReadonlyMap<string, readonly FontFace[]>,
): string | undefined => {
	if (!variable) {
		return undefined;
	}

	// Prefer the primary-axis normal file, but fall back to the italic file.
	const axisKey = determineAxisKey(variable);
	const normalKey = `${axisKey}.css`;

	if (facesByCSSFile.has(normalKey)) {
		return normalKey;
	}

	const italicKey = `${axisKey}-italic.css`;
	return facesByCSSFile.has(italicKey) ? italicKey : undefined;
};

// One resolved face can feed multiple published CSS files, for example a static
// italic face contributes to both `400-italic.css` and `latin-italic.css`.