halostatue
Enviable - Robust environment variable conversion
Enviable is a small collection of functions to make working with environment variables easier when configuring Elixir projects. It is designed to work configuration environment loaders like Dotenvy and provides robust value conversion like jetenv.
This has been published several times over the last few weeks, but I just completed a new feature (delimited list conversion) and figure that it’s worth sharing with the community now. This works best when using “12 Factor” configuration via environment variable.
# config/runtime.exs
import Config
import Enviable
client = fetch_env!("CLIENT")
Dotenvy.source([".env", ".env.#{client}", get_env()])
# Before
#
# config :my_app,
# key: System.fetch_env!("SECRET_KEY"),
# port: System.fetch_env!("PORT") |> String.to_integer(),
# ssl: System.get_env("SSL_ENABLED") in ~w[1 true]
# After
config :my_app,
key: fetch_env!("SECRET_KEY"),
port: fetch_env_as_integer!("PORT"),
ssl: get_env_as_boolean("SSL_ENABLED")
Because this is intended for use at configuration startup in a controlled environment, it offers options which would normally be considered unsafe, such as unconstrained atom conversion (fetch_env_as_atom!) while encouraging developers to consider safer options:
# This is allowed but is not recommended.
fetch_env_as_atom!("MY_ATOM_VALUE")
# This is allowed but can still provide unexpected values.
fetch_env_as_safe_atom!("MY_ATOM_VALUE")
# This is better than either of the above—and works as `atom` or `safe_atom` variants:
fetch_env_as_atom!("MY_ATOM_VALUE", allowed: [:red, :green, :blue])
It has been heavily influenced by jetenv for the breadth of conversion, but I have extended its conversion range substantially.
I push for 100% coverage of all branches, and have special attention paid to negative cases. I’m not currently using property checking, but it may be the next thing added. I’ve also tried to make sure that the documentation is comprehensive for all of the supported options, to the point where there’s 30% more @doc lines than there are code lines with doctests for most functions.
- Hex: enviable | Hex
- HexDocs: Enviable v1.7.0 — Documentation
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halostatue
I just released Enviable v1.5, which is mostly a bugfix release, but added a couple of minor features.
I’m not sure when (or if) Enviable 2 will be released, but when it does, the default behaviour of boolean conversion will be to be case-insensitive. To make that transition easier, I added a compile-time option (:enviable, :boolean_downcase) that can be set to :default to match the eventual default and keep your fetch_env_as_boolean! calls simpler).
Although get_env_as_json and related functions documented that the default engine could be configured with :enviable, :json_engine, the code supporting that was incorrect in two ways: it was being evaluated at runtime, not at compile time, and it was using :enviable, :json instead of :enviable, :json_engine. This has been fixed and specifying the JSON engine now allows for an MFA tuple either as a parameter or as a compile configuration.
Changelog
-
Fixed a bug with
listconversion forget_env_as_listandget_env_aswhere support for a:defaultvalue was not included. -
Fixed a bug with
:downcaseconversions and nil values. -
Added a compile-time configuration option to change the default boolean
:downcaseoption. The default value is currentlyfalse(do not downcase). The next major version of Enviable will change this to:default, as it should not matter whether the matched value istrue,TRUE, orTruefor boolean tests. -
Added
:upcaseoption toatomandsafe_atomconversions. -
Fixed
:json_engineconfiguration so that it is properly compile-time and referenced. The JSON parsing code was looking this up at runtime under the wrong key. -
Added support for
{m, f, a}specification for:json_engineconfiguration or the:engineparameter for JSON conversion.
halostatue
I have forgotten to post two updates released in the last few months, so:
Enviable 1.6 (2025-08-12)
Added support for as_decimal conversions supporting Decimal.
Added JSON support for the built-in JSON module for Elixir 1.18 and later.
Enviable 1.7 (2025-10-15)
Added support for as_timeout conversions supporting timeout values processed through to_timeout/1 on Elixir 1.17 or later. (This feature is not exposed for earlier versions.)
The parser for timeout conversions (this supports
3m2sfor 3 minutes and two seconds) was built with LLM assistance using Kiro. The initial prompt used the description in Timeout Values as its core and the parser was built withnimble_parsec.
Note that the next version of Enviable will probably be Enviable 2.0 and it will explicitly only support Elixir 1.17 or later.
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