DesEnv-rs

Environment variables deserializer library.

With this library is possible to deserialize a bunch of environment variables in a more structured data type.

Install

```toml

Cargo.toml

[dependencies] desenv = "0.1.0" ```

Usage

The library expose a utility function to load the configuration from environment variables rust fn main() { let _config: Config = desenv::load().expect("Failed to load configuration"); }

Then Config should be something like this

```rust use desenv::Desenv;

[derive(Desenv)]

pub struct Config { field1: String, field2: String, } ```

In order to have a successful loaded Config it's needed that in the env there are two variables: - FIELD1 - FIELD2

Customize configuration

It is possible to customize how the configuration is loaded.

Rename

Using rename modifier on desenv field attribute is possible to instruct the library to look for a different variable. In the example above, while loading the configuration, the library will try to find the FIELD_1 variable.

```rust use desenv::Desenv;

[derive(Desenv)]

pub struct Config { #[desenv(rename = "FIELD_1")] field1: String, } ```

Pay attention because rename attribute is case-sensitive. So in an example like the above one the library will try to find an environment variable called downcased_field_1.

```rust use desenv::Desenv;

[derive(Desenv)]

pub struct Config { #[desenv(rename = "downcasefield_1")] field1: String, } ```

Default

With this modifier is possible to instruct the library to deserialize an environment variable with a default value.

With value

If the FIELD1 environment variable does not exist the library will fill field1 with value.

```rust use desenv::Desenv;

[derive(Desenv)]

pub struct Config { #[desenv(default = "value")] field1: String, } ```

or

```rust use desenv::Desenv;

[derive(Desenv)]

pub struct Config { #[desenv(default(value = "value"))] field1: String, } ```

With env

If the FIELD1 environment variable does not exist the library will try to load, as fallback, the FALLBACK_FIELD1 environment variable. If FALLBACK_FIELD1 does not exist too, then the load will fail.

```rust use desenv::Desenv;

[derive(Desenv)]

pub struct Config { #[desenv(default(env = "FALLBACK_FIELD1"))] field1: String, } ```

With std default

If the FIELD1 environment variable does not exist the library will fill field1 with the Default implementation for that type. So, for example, for a string the default will be an empty string.

```rust use desenv::Desenv;

[derive(Desenv)]

pub struct Config { #[desenv(default)] field1: String, } ```

Separator

Instruct the library on how to deserialize a string to a vector performing a split over the string. The provided value must be a char. Cannot be used on non-vector fields.

```rust use desenv::Desenv;

[derive(Desenv)]

pub struct Config { #[desenv(separator = ';')] field1: String, } ```

Nested

Tells the library that the specified field shouldn't be deserialized using an environment variable but using Desenv macro too.

```rust use desenv::Desenv;

[derive(Desenv)]

pub struct Config { #[desenv(nested)] field1: NestedConfig, }

[derive(Desenv)]

pub struct NestedConfig { field: String, } ```

Prefix

If set apply that prefix for every environment variable deserialized. In the example below field1 will be deserialized as PREFIXED_FIELD1. Note that prefix is case-sensitive.

```rust use desenv::Desenv;

[derive(Desenv)]

[desenv(prefix = "PREFIX_")]

pub struct Config { field1: String, } ```

If prefixed struct has a prefixed nested struct the result will be a concatenation of both the prefixes. In the example the field in NestedConfig will be resolved using PARENT_NESTED_FIELD environment variable.

```rust use desenv::Desenv;

[derive(Desenv)]

[desenv(prefix = "PARENT_")]

pub struct Config { #[desenv(nested)] field1: NestedConfig, }

[derive(Desenv)]

[desenv(prefix = "NESTED_")]

pub struct NestedConfig { field: String, } ```

OsString

OsStrings are supported for some specific cases where an environment variable is not utf8 encodable.

```rust use std::ffi::OsString; use desenv::Desenv;

[derive(Desenv)]

pub struct Config { field1: OsString, } ```

Supported types

Right now every T that mix-in the FromStr trait could be used as simple fields. Other supported types are: - Option<T> - Vec<T> - OsString