INI format support

[jpmckinney]

I use INI.

(If you're wondering why, I prefer to spare my (often non-technical) users from having to worry about significant whitespace (YAML), syntax errors and escape characters (JSON, TOML, XML, YAML), nesting errors (XML, YAML) – and I want to provide in-line documentation via comments (not in JSON).)

[SergioBenitez]

I'd be happy to add support for INI. Last I checked, there was no obvious candidate for a serde support crate we could use. Has this changed? If so, I'd be happy to accept a PR. The implementation is almost trivial as it's a simple implementation of the Format trait already automated by an existing macro (this is how the Json and Toml implementations are generated).

[jpmckinney]

config-rs uses https://docs.rs/rust-ini/latest/ini/, but serde support is an open issue zonyitoo/rust-ini#40

I haven't looked at https://github.com/arcnmx/serde-ini

[SergioBenitez]

Figment is built around serde, so the crate must support serde, and support it rather well. serde-ini hasn't seen a commit in a couple of years, and a few of its open issues call for features that seem like those one would expect, like arcnmx/serde-ini#8, so I'm not sure it's developed enough for us to include it directly. If you find another library, please feel free to reopen this issue or submit a PR.

Otherwise, please note that you can trivially implement support for INI entirely outside of Figment by implementing the Format trait. An implementation using serde-ini would look like this:

struct Ini;

impl Format for Ini {
    type Error = serde_ini::de::Error;

    const NAME: &'static str = "INI";

    fn from_str<'de, T: DeserializeOwned>(string: &'de str) -> Result<T, Self::Error> {
        serde_ini::de::from_str(string)
    }
}

Then you can use it just like Toml or Json:

use figment::providers::Format;

Figment::new()
    .merge(Ini::file("myapp.conf"))
    .join(Ini::file("defaults.conf"))