glenv

Type-safe environment variables for Gleam.

Accessing environment variables doesn’t give us the type of safety guarantees we’d like in a langauge like Gleam. glenv aims to guarantee that each environment variable is of the correct type AND is present.

gleam add glenv

import dot_env
import gleam/decode
import glenv

pub type MyEnv {
  MyEnv(hello: String, foo: Float, count: Int, is_on: Bool)
}

pub fn main() {
  // Optional: Load environment variables from a file
  dot_env.load_default()

  let definitions = [
    #("HELLO", glenv.String),
    #("FOO", glenv.Float),
    #("COUNT", glenv.Int),
    #("IS_ON", glenv.Bool),
  ]

  let decoder =
    decode.into({
      use hello <- decode.parameter
      use foo <- decode.parameter
      use count <- decode.parameter
      use is_on <- decode.parameter

      MyEnv(hello: hello, foo: foo, count: count, is_on: is_on)
    })
    |> decode.field("HELLO", decode.string)
    |> decode.field("FOO", decode.float)
    |> decode.field("COUNT", decode.int)
    |> decode.field("IS_ON", decode.bool)

  let assert Ok(env) = glenv.load(decoder, definitions)

  env.hello == "hello"
  env.foo == 1.0
  env.count == 1
  env.is_on == True
}

Expected values

Bool

Any casing of true, yes or 1 will be parsed as True. Any other value will be parsed as False.

Float

Any value that can be parsed as a float will be parsed as a float. Any other value will result in an InvalidEnvValue error.

Int

Any value that can be parsed as an int will be parsed as an int. Any other value will result in an InvalidEnvValue error.

String

Any value will be parsed as a string.

Further documentation can be found at https://hexdocs.pm/glenv.

Development

gleam run   # Run the project
gleam test  # Run the tests
gleam shell # Run an Erlang shell