Print string only if metadata is set

[UtkarshVerma]

I wish to replicate the following mpc format in playerctl:

mpc -f "%title%[ - %artist%]" current

It only prints - %artist% if artist is set. How do I achieve this with playerctl?

[hseg]

Same here - am currently hackily using a combination of default() and stripping the default substitution I'm setting.

my $metadata = qx(playerctl $player_arg metadata \\
        --format '{{default(artist, "\004\005")}} - {{title}}' 2>/dev/null);
chomp $metadata;
$metadata =~ s/^\004\005 - //;

(that pair of characters is STX/ETX, probably semantically invalid but it makes some sense to me)