Mirrord Config Derive

This crate implements the derive macro MirrordConfig, which introduces the config attribute:

On a struct:
- map_to = &str set the name of the new generated struct (defaults to format!("File{}", <struct name>)).
- derive = &str extend derive statement with extra values.
- generator = &str set the type Generator for FromMirrordConfig.
On struct fields:
- nested to use a value of a type that itself implement MirrordConfig. The value used is its Generated type.
- toggleable wrap field with ToggleableConfig so will be allowed to pass bool instead of entire field
- env = &str to load the value from the specified environment variable, if it's populated.
- default = &str to set a default value to the field. This also implicitly unwraps it.
- unstable mark field as unstable and print an error message to the user.
- deprecated | deprecated = &str mark field as deprecated and print either a default message or a custom one.
- rename = &str pass #[serde(rename = &str)] to generated struct.

Example

rust

/// MyConfig Comments
#[derive(MirrordConfig, Default)]
#[config(map_to = "MyFileConfig", derive = "Eq,PartialEq")] // If map_to isn't given, it will default to FileMyConfig
pub struct MyConfig {
    /// Value 1 Comment
    #[config(env = "VALUE_1")]
    pub value_1: Option<String>,

    /// Value 2 Comment
    #[config(env = "VALUE_2", default = "2")]
    pub value_2: i32,

    /// Value 3 Comment
    #[config(env = "VALUE_3", rename = "foobar")]
    pub value_3: String,

    /// Value 4 Comment
    #[config(nested)]
    pub value_4: OtherConfig,
}

The following struct will be generated:

rust

/// MyConfig Comments
#[derive(Clone, Debug, Default, serde::Deserialize, Eq, PartialEq)]
#[serde(deny_unknown_fields)]
pub struct MyFileConfig {
    /// Value 1 Comment
    pub value_1: Option<String>,

    /// Value 2 Comment
    pub value_2: Option<i32>,

    /// Value 3 Comment
    #[serde(rename = "foobar")]
    pub value_3: Option<String>,

    /// Value 4 Comment
    pub value_4: Option<<OtherConfig as FromMirrordConfig>::Generator>,
}