I think from your code
add_action( 'wp_footer', 'purewpns_googlefont_loader' );
Function purewpns_googlefont_loader maybe typo mistake.
You use the action wp_footer and added empty array which obviously print empty array.
Okay. You can use:
googlefont_filter_callback( $font );
Except
$fonts = apply_filters( 'googlefont_loader', $fonts );
In function googlefont_loader()
And add filter in function googlefont_filter_callback like:
function googlefont_filter_callback( $fonts=array() ) {
return apply_filters( 'googlefont_loader', $fonts );
}
Now you’ll be able to access fonts from both short code.
E.g.
add_filter( 'googlefont_loader' function( $fonts ) {
var_dump( $fonts);
return $fonts;
});
But it affect on both short code. You can introduce another individual filters for each shortcode.