Env Settings

Env Settings is a Rust library that helps you to initialize structs using environment variables

This Rust library took inspiration from pydantic's BaseSettings Python class

Installation

shell cargo add env-settings cargo add env-settings-derive

Usage

When you add the EnvSettings derive to a struct, two methods are added to it

• rust fn from_env(...) -> env_settings_utils::EnvSettingsResult<Self>

  It creates a new instance using just the environment variables. If something fails, it returns an env_settings_utils::EnvSettingsError error

• rust fn new(...) -> env_settings_utils::EnvSettingsResult<Self>

  It creates a new instance using a combination of environment variables and parameters. More in detail, every field value can be passed as parameter wrapped in an Option object. Then if the parameter is Some, it is used, otherwise the value is recoved from the environment variables. If something fails, it returns an env_settings_utils::EnvSettingsError error

Basic

shell export name=paolo export favourite_number=42

```rust use envsettingsderive::EnvSettings;

[derive(EnvSettings)]

struct MyStruct { name: String,

favourite_number: u8,

}

fn main() { let mystruct = MyStruct::fromenv().unwrap(); asserteq!(mystruct.name, "paolo".tostring()); asserteq!(mystruct.favouritenumber, 42);

let name = "luca";
let my_struct = MyStruct::new(Some(name.to_string()), None).unwrap();
assert_eq!(my_struct.name, name);
assert_eq!(my_struct.favourite_number, 42);

} ```

Advanced

shell echo "MY_STRUCT_FAVOURITE_NUMBER=42\n" > .env export MY_BIRTH_DATE=01/01/1970

```rust use envsettingsderive::EnvSettings;

[derive(EnvSettings)]

[envsettings(caseinsensitive, filepath = ".env", prefix="MYSTRUCT_")]

struct MyStruct { #[env_settings(default = "paolo")] name: String,

favourite_number: u8,

#[env_settings(variable = "MY_BIRTH_DATE")]
birth_date: String,

birth_place: Option<String>,

#[env_settings(skip)]
friends: Vec<String>,

}

fn main() { let friends = vec!["luca".tostring()]; let mystruct = MyStruct::fromenv(friends.clone()).unwrap(); asserteq!(mystruct.name, "paolo".tostring()); asserteq!(mystruct.favouritenumber, 42); asserteq!(mystruct.birthdate, "01/01/1970"); asserteq!(mystruct.birthplace, None); asserteq!(my_struct.friends, friends);

let name = "luca";
let my_struct = MyStruct::new(
    Some(name.to_string()),
    None,
    None,
    Some("london".to_string()),
    friends.clone(),
).unwrap();
assert_eq!(my_struct.name, name);
assert_eq!(my_struct.favourite_number, 42);
assert_eq!(my_struct.birth_date, "01/01/1970");
assert_eq!(my_struct.birth_place, Some("london".to_string()));
assert_eq!(my_struct.friends, friends);

} ```

Parameters

Struct

The current supported parameters for the structs are:

• case_insensitive: whether the environment variables matching should be case insensitive. By default, matching is case sensitive.
• delay: whether to delay the lookup for environment variables from compilation time to run time. By default the lookup is performed at compilation time
• file_path: the file path to read to add some environment variables (e.g. .env). By default, it is not set
• prefix: the prefix to add to the name of the struct fields before matching the environment variables. By default, it is not set

Field

The current supported parameters for the fields are:

• default: the default value to use if the environment variable is not found. By default, it is not set
• skip: whether to skip the parsing of the environment variable. It is necessary if the type specified does not implement std::str::FromStr.
• variable: the environment variable to use for the lookup. By default, the name of the field

Variables resolution hierarchy

1. Arguments passed to the new method (if using new).
2. Environment variables
3. Variables loaded from a file (e.g. .env)
4. Default values

Contribute

Before starting to work on a contribution please read:

• Code of Conduct
• Contributing
• Goverance
• Security
• Support

Run tests

When testing run:

shell cargo test -- --test-threads=1

to prevent tests from competitively interacting with the same file

License

This project is licensed under the terms of the MIT or Apache 2.0 license.