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How is TOML bad as a config language? I would not transmit data in TOML but is makes a lot of sense as a config language.

• 0xbadcafebee 6y ago
  Neither YAML or TOML are config languages, they are data formats. A data format is a way of structuring or serializing data. The whole point of the format is to read and write arbitrary data. It may have a simple schema, or features designed for the loading and unloading of data. But all those features are designed to assist the machine, not the human operator. A config format is designed specifically to assist a human operator, not a program. Humans should not have to consider data types when they write a config, or when they feed it to a program. Humans should have useful features to make their lives easier, like variable substitution, pattern matching, inheritance, namespaces, simple newline-separated whitespace-indifferent commands, etc. Programming languages are just elaborate configuration formats. And that's where the problem begins: how much "power" do you give the configuration format before it gets unruly? It's difficult to find a balance. People end up using simple data formats because the parsers are widely available and they can "fake" advanced features by making programs interpret a specifically-crafted data structure as a configuration instruction. But there's very little thought put into how this can be extended to make more complex configurations easier. Most web servers and other complex software [usually run by sysadmins] have a real configuration format or configuration language. Poorly-written software pretends a data format is a programming language, or even worse, forces you to use an actual programming language. These designers fundamentally don't understand or don't care about the user.