HOCON configuration for every Scala platform.

What this is

hocon is a pure-Scala implementation of HOCON (Human-Optimized Config Object Notation) — the comfortable, JSON-superset config format popularized by Lightbend’s com.typesafe:config.

com.typesafe:config is JVM-only — it reaches for java.io, the classpath, java.util.regex, and java.time — which leaves Scala.js and Scala Native with no good way to read a .conf file. hocon fills that gap: the whole library is plain Scala 3 in a shared source set, with no java.* imports and no regex engine in its core, so the same code runs on all three platforms.

import io.github.edadma.hocon.*

val config = Hocon.parse("""
  en {
    greeting = "Hello, world"
    nav { home = "Home", about = "About" }
    cart.items = "{count} items"   # path-expression key
  }
""")

config.getString("en.greeting")    // "Hello, world"
config.getString("en.nav.home")    // "Home"
config.hasPath("en.missing")       // false

Why HOCON for i18n

HOCON is a natural fit for internationalization message files: nested, commented, human-friendly, and far less noisy than JSON. hocon ships a small Messages helper for the {name} placeholder pattern, and Phase 2’s merging makes a base locale with per-locale overrides a one-liner.

val base = Hocon.parse("""greeting = "Hello", farewell = "Goodbye"""")
val fr   = Hocon.parse("""greeting = "Bonjour"""")

val messages = Messages(fr.withFallback(base))
messages("greeting")   // "Bonjour"  (translated)
messages("farewell")   // "Goodbye"  (from the base locale)

What you get today

• A full lexer and parser — comments (# and //), quoted strings with escapes, triple-quoted multi-line strings, numbers, booleans, null, nested objects, arrays, and path-expression keys (a.b.c = v).
• An untyped Config API — typed getters (getString, getInt, getBoolean, getConfig, getList, …) with *Opt variants, hasPath, and clear exceptions.
• Object merging and fallback — withFallback and Hocon.load, with recursive object merge and last-wins layering.
• Substitutions — ${path} and optional ${?path}, resolved against the merged root, with environment fallback and cycle detection.
• Value concatenation — joining strings, arrays, and objects written side by side ("http://"${host}, [1] [2], ${defaults} { … }).
• Durations and sizes — getDuration (10s, 5 minutes) and getBytes (512K, 10MB).
• Includes — include "other.conf" (and file/url/classpath/required forms) behind a pluggable, per-platform ConfigSource.
• A typed decoder — config.as[A] maps a document onto a case class, with automatic Mirror-derived decoders for nested case classes, Option, List, and Map.
• Full path expressions and array append — quoted path segments, +=, and self-referential substitutions, conformant with the HOCON spec.
• An i18n sidecar — Messages with placeholder interpolation.

Every phase on the roadmap is complete.

Where to go next

• Getting Started — add the dependency and parse your first config.
• Guide — the HOCON format hocon supports, merging and fallback, and the roadmap.
• Reference — the Config API and the Messages helper.