[the_mitsuhiko]

Which ones would that be?

[phloxicon]

YAML is quite mature, clean, is a superset of JSON so people could use JSON if they wanted, and it's used for config files for pub, Dart's package manager. TOML doesn't seem mature enough.

[bjz_]

TOML is extremely simple. YAML on the other hand is incredibly hard to implement. JSON has no comments and is not really that nice for humans.

[mateuszf]

How about s-expressions :) ?

[bokchoi]

Or edn?

https://github.com/edn-format/edn

[bjz_]

That would be my choice, but TOML is good enough for me :)

[kodablah]

HOCON: https://github.com/typesafehub/config

[nimish]

toml is unstable and has no real spec + YAML has a well defined spec and is widely used?

[Ygg2]

YAML spec is also super complicated and writing parser for it is non-trivial (for comparisson YAML has ~150 EBNF rules while XML with DTD has about ~80)! I'm not comparing validation rules but they are probably about the same.

This complexity means there is already a parser for TOML, and not one for YAML. That's IMO main reason they went with TOML.

[steveklabnik]

There are actually already MULTIPLE parsers for TOML in Rust, and Cargo switched between the two yesterday.

As you say, this is a testament to TOML's simplicity.

EDIT: Furthermore, TOML is going to have a 1.0 soon: https://github.com/rust-lang/cargo/issues/46