venera

• venera
  • sources
  • usage
  • custom loaders
  • todo

Another config loader, intended for loading configuration files for services. For libraries, consider something like cosmiconfig. This is mostly for my own use because I can't find a single library that does what I want, but it's free for anyone to use, as long as you're fine with subpar documentation.

sources

If multiple sources are found, they will be merged with loaders last in options.loaders taking priority.

• --arg="values" from process.argv
• Environment variables, prefixed with the app name.
  • Prefixed keys are required - if your app name was "Atlas", you should define keys as ATLAS_API_KEY and ATLAS_API_SECRET.
  • For nested values, use double underscores. ATLAS_CLIENT__KEY will be accessible as client.key
• .env files in the current directory or up.
  • .env and .env.local in any environment
  • .env.staging, .env.development, .env.production, .env.test in their respective environments based on process.env.NODE_ENV
  • Prefixes are required in .env files to prevent ambiguity with process.env variables that also require a prefix. Keys without a prefix are ignored.
  • Double underscores are supported for nested keys. CLIENT__KEY would be loaded as client.key
  • If there are multiple environment files found such as .env and .env.staging, their values will be merged preferring values from .env.staging.
• Config files in the locations you would expect.
  • JSON files are supported with or without paths, such as .apprc. Comments are supported.
  • For other formats, an extension is required to remove ambiguity. For YAML, you would use .apprc.yaml, etc.

usage

import { loadConfig } from "@ryanke/venera";

mockFS({
  // prefixed environment variables
  "./.env": "MYAPP_REDIS__PASSWORD=youshallnotpass",
  // numbers/booleans in env variables will be parsed as numbers/booleans
  "./.env": "MYAPP_REDIS__PORT=6379",
  // config files in standard locations or in any current/parent directory
  "./.myapprc.json": JSON.stringify({
    message: "Very cool",
    redis: {
      // override default values
      host: "127.0.0.1",
    },
  }),
});

const data = loadConfig("myapp", {
  // if you want to add another file path, you can do so here.
  // this only works if a loader implements `pathHints`.
  // fs loaders do (yaml, json, toml currently). anything else is silently ignored.
  pathHints: ["config.yaml"],
});
// data now looks like:
// {
//   message: "Very cool",
//   redis: {
//     host: "127.0.0.1",
//     password: "youshallnotpass",
//     port: 6379,
//   },
//   Symbol(sourcePaths): ['/wherever/.myapprc.json', '/wherever/.env']
// }

// "zod" is a great option to parse the resulting schema.
// this is of course optional, by this point its just an object.
const config = validateConfig(data);
export { config };

custom loaders

import { loadConfig, constantCaseToPath, DEFAULT_LOADERS, Loader, LoaderContext } from "@ryanke/venera";

export class MyLoader extends Loader {
  load(appName: string, context: LoaderContext): Record<string, any> {
    context.sourcePaths.push("/some/path/this/loader/loaded");
    context.pathHints; // present if passed to loadConfig()

    return {
      // its up to the loader to handle converting keys to camel case, unflattening the result, etc.
      // you can look at the included loaders for more info, specifically the .env or arg loader.
      // constantCaseToPath and the "flat" npm package is useful.
      someKey: "someValue",
      anotherKey: "anotherValue",
    };
  }
}

const data = loadConfig<Partial<AppConfig>>("app-name", {
  // the order of loaders is respected, loaders towards the end are preferred when merging
  // values from multiple sources. You can also instantiate the loader yourself if you have
  // to pass constructor parameters.
  loaders: [...DEFAULT_LOADERS, MyLoader],
});

todo

• [ ] Option to turn off merging and instead just return the first config found. This would have to be implemented per-loader to make sense, because I think it would be nice if you could turn off merging and still override .rc values with environment variables, sometimes its just convenient.
• [ ] Output sources for each config value, maybe even per-property with symbols declaring which properties are from where so you could do something like The key CLIENT_TOKEN in config /home/user/.env is invalid or something.
• [ ] TOML/INI support? The more file system loaders are added the more startup slows down checking for all of them, realistically I think YAML is as human-readable as you need anyway, but it would be nice to throw in.