Config Precedence

viper manages configuration from multiple sources. When you call v.get(key), it checks each source in priority order and returns the first match.

Priority Order (highest to lowest)

Priority	Source	Set via
1	Override	v.set(key, value)
2	Environment variable	v.bindEnv() / v.automaticEnv()
3	Config file	v.readInConfig()
4	Default	v.setDefault() / v.setDefaults()

Example

import { createViper } from '@caterpillar-soft/viper'

const v = createViper()

// Priority 4: default
v.setDefault('port', 3000)
v.get('port') // 3000

// Priority 3: config file overwrites default
v.mergeConfigMap({ port: 8080 })
v.get('port') // 8080

// Priority 2: env var overwrites config
v.setEnvPrefix('APP')
v.automaticEnv()
// With APP_PORT=9090 in environment:
v.get('port') // '9090'

// Priority 1: override wins over everything
v.set('port', 4000)
v.get('port') // 4000

Case Insensitivity

All keys are normalized to lowercase internally. These are all equivalent:

v.set('Database.Host', 'myhost')
v.get('database.host') // 'myhost'
v.get('DATABASE.HOST') // 'myhost'
v.get('Database.Host') // 'myhost'

Environment Variable Types

Environment variables are always strings. If you need a number or boolean, use the typed getters:

// APP_PORT=8080
v.getNumber('port') // 8080 (number, not string)
v.getBoolean('debug') // true (for "true" or "1")