fiction

Package Version Hex Docs

Jonathan Frakes telling you it's fiction

A library to help combine app configuration from multiple sources into a single record. This core is pure gleam, though most useful providers will have target-specific code.

Heavily inspired by Figment

Usage

gleam add fiction@2

importgleam/dynamic/decodeimportfiction// this is provided by the separate package `fiction_toml`
importfiction/providers/toml// this is provided by the separate package `fiction_env`
importfiction/providers/envtypeConfig{Config(port:Int,host:String)}fnconfig_decoder(){// The decoder can provide defaults if you want
useport<-decode.optional_field("port",5432,decode.int)// Or handle more complicated keys
usehost<-decode.one_of(decode.at(["host"],decode.string),[decode.at(["tools","app","dev","host"],decode.string)])decode.success(Config(port:,host:))}pubfnmain()->Nil{letassertOk(config)=// providers are layered onto a Builder with each layer being combined with all previous layers
// the function used (`join`, `merge`, `concat_join`, or `concat_merge`) determines the strategy use when keys conflict
// this can be used to give sources precendence over others
fiction.new()// for example, the base values could come from `app.toml`
|>fiction.join(toml.file("./priv/app.toml"))// next we can layer some common environment variables on top using `merge` to overwrite any conflicting keys
|>fiction.merge(env.exact(["PORT","HOST"]))// then we can layer relevant environment variables, again using `merge`
// in this example, if `app.toml` had a top-level `port` key, then defining `APP_PORT` would overwrite that value
|>fiction.merge(env.prefixed("APP_"))// we can include `gleam.toml` too, using `concat_join` to preserve the values of existing keys, but concatenating any list values together
|>fiction.concat_join(toml.file("./gleam.toml"))// providers are just plain functions, so anything that returns a Result(List(#(String, fiction.Value)), String) will work as well
// in this case using `join` will provide a default value for the `host` key without overwriting that value if it's been set already
|>fiction.join(fn(){Ok([#("host",fiction.String("localhost"))])})// finally we extract the values we want into a single record with a standard gleam decoder that can be as simple or complicated as you need
|>fiction.extract(with:config_decoder())}

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

Providers

• fiction_toml - A simple TOML provider utilizing simplifile and tom
• fiction_env - An environment provider utilizing envoy

Development

gleam test # Run the tests