declarative-env

This crate contains a macro for generating a struct which reads the environmental variables defined in the configured file.

This allows to have a single point of definition for the env configuration, thus avoiding a possible incoherence between the documentation and the implementation.

Usage

The macro must be attached to an empty struct definition:

   #[declarative_env!(path = "./example.hjson", format = "hjson")]
   struct MyConfig;

Note: the struct can have any visibility.

The macro creates a struct with the same name of the empty struct, but it injects as fields all the variables defined in the path keyword.

For example, the definition file:

SERVER_PORT: {
   type: u16
   description: The port the server will listen on
   default: 8080
}

generates the struct

struct MyConfig {
   SERVER_PORT: u16,
}

The path of the definition file is relative to the cargo manifest dir (the one with Cargo.toml).

The supported formats are specified in the AcceptedFormat enum; formats are the lowercase version of the enum variants, so AcceptedFormat::Hjson is selected with format = "hjson".

Env Variable Definition

The env variable definition file contains a map of objects, where the key is the name of the env variable, and the value contains the metadata of the variable:

• the type (accepted types are defined in AcceptedRustType).
• the description, unused in generated code, required for documentation purpose.
• the default value, optional (it must be parsable as the defiend type).

Accepted formats

Supported formats are listed in the AcceptedFormat enum.

Accepted types

Types variables can be are listed in the AcceptedRustType enum.

License

This project is distributed according to the Mozilla Public License 2.0.