dotenvy-derive

Proc macro that derives struct initialization from .env files at compile time via dotenvy_macro.

Usage

Add to Cargo.toml:

[dependencies]
dotenvy-derive = "0.15"
dotenvy_macro = "0.15"

`impl Default` (standard)

use dotenvy_derive::Bind;

#[derive(Bind)]
pub struct MailConfig {
    #[env("MAIL_HOST")]
    pub host: &'static str,
    #[env("MAIL_API_KEY")]
    pub api_key: &'static str,
}

let config = MailConfig::default();

Generates:

impl Default for MailConfig {
    fn default() -> Self {
        MailConfig {
            host: ::dotenvy_macro::dotenv!("MAIL_HOST"),
            api_key: ::dotenvy_macro::dotenv!("MAIL_API_KEY"),
        }
    }
}

`pub const INSTANCE` (static)

Add #[env_static] to emit a compile-time constant instead:

use dotenvy_derive::Bind;

#[derive(Bind)]
#[env_static]
pub struct MailConfig {
    #[env("MAIL_HOST")]
    pub host: &'static str,
    #[env("MAIL_API_KEY")]
    pub api_key: &'static str,
}

// Use in const context:
pub const CONFIG: AppConfig = AppConfig {
    mail: MailConfig::INSTANCE,
};

Generates:

impl MailConfig {
    pub const INSTANCE: MailConfig = MailConfig {
        host: ::dotenvy_macro::dotenv!("MAIL_HOST"),
        api_key: ::dotenvy_macro::dotenv!("MAIL_API_KEY"),
    };
}

Requirements

All fields must be &'static str — dotenv! returns &'static str
A .env file must exist at the crate root at build time
Consumer crate must depend on dotenvy_macro directly

Error handling

The macro emits a compile error for:

Non-struct types (enums, unions)
Tuple or unit structs
Fields missing #[env("VAR_NAME")]
Malformed #[env(...)] attribute

License

MIT

dotenvy-derive 0.15.8