Node dependent reasonml config library


npm version Known Vulnerabilities

Config library for nodejs, similar to node-config but strongly typed with validated type parsing. No need for Js.Nullable.t shims typical when just binding to js-libs. Configuration data is a JSON Object loaded by a loader function (see below).


npm install @veikkaus/re-node-config

And to bsconfig.json: "bs-dependencies": [..., "@veikkaus/re-node-config", ...],

Usage Examples

Assuming You Write file MyConfig.re:

module C = VeikkausReNodeConfig.Config;

 * loadConfig with default options searches for .json and .yaml files from ./config/
 * (loading may produce an error, therefore using getExn, which will throw if loading had errors)
let config: C.t = C.loadConfig() |> C.getExn;

Usage in other files/modules:

module C = VeikkausReNodeConfig.Config;
let config = MyConfig.config;

let host: string = C.getString("server.host", config);
let port: int = C.getInt("server.port", config);

/* getString is actually a convenience function which combines the following detailed functionality:
 *   getString = (path, config) => config |> C.key("server.host") |> C.parseString |> C.getExn;
 *   meaning ~ get a string value from the defined configuration path or throw exception MissingKey or
 *             TypeMismatch

/* Parsing lists of values is fairly simple too: */
let myList: list(string) = config |> C.key("listOfWords") |> C.parseList(C.parseString) |> C.getExn;

/* Finally providing that you implement a parser from json to your own type: */
type foo;
let myJsonToFoo: Js.Json.t => foo;     /* May throw on parsing errors */
/* then that can be used to turn complicated object on your config into your custom type: */
let myFoo: foo = config |> C.key("foo") |> C.parseCustom(myJsonToFoo) |> C.getExn;

Config loading

Function C.loadConfig() searches config values from following sources in following order: 1. Loads config files from directory defined by NODE_CONFIG_DIR env variable if it exists, or otherwise from directory process.cwd() + "/config/": 1. File default.{json,yaml} is loaded if it exists 2. File ${NODE_CONFIG_ENV}.{json,yaml} is loaded if it exists, and if not, then and only then ${NODE_ENV}.{json,yaml} is loaded if that exists. 3. File local.{json,yaml} is loaded if exists. 2. Loads Environment Variables 1. Loads CONFIG_JSON contents 2. Reads file custom-environment-variables.{json,yaml}, which contains ENV variable name override definitions for various config keys (this is identical to: node-config), -> loads overrides from the defined env variables that are found. JSON parsing is attempted to the values of the env variables, enabling e.g. passing lists inside one env variable: MYVAR='["first","second"]'. If the attempted JSON parsing fails, the value is treated as a simple string e.g. MYVAR2="value2" (= simple string. note that json would need extra quotations: "\"value2\"") 3. Fallback to empty config if nothing from the above exists.