We're talking about templating and generating files, but it seems like everyone has just collectively forgotten about M4?
Yes, it can be unsafe if you're not careful, but if you need to bang out a quick prototype it's the best tool there is. It's part of POSIX, and so it will always be available, the language is dead simple, and you can generate any text you want with it.
I wouldn't use it with YAML, but I would probably never template YAML in the first case: just generate JSON and feed it through `yq -y` if you need a quick YAML generator.
Yes, it can be unsafe if you're not careful, but if you need to bang out a quick prototype it's the best tool there is. It's part of POSIX, and so it will always be available, the language is dead simple, and you can generate any text you want with it.
I wouldn't use it with YAML, but I would probably never template YAML in the first case: just generate JSON and feed it through `yq -y` if you need a quick YAML generator.