Creates a ConfigProvider backed by an in-memory JavaScript value (typically a parsed JSON object).

When to use

Use when you need deterministic config from an in-memory JavaScript value, such as in tests, embedded config, or parsed JSON.

Details

Path traversal follows standard JS rules: string segments index into object keys, numeric segments index into arrays. Returns undefined for any path that cannot be resolved. Never fails with SourceError.

Primitive values (number, boolean, bigint) are stringified via String(...).

Literal empty strings are treated as missing values when loaded as values by default. Pass { preserveEmptyStrings: true } to keep empty strings as explicit values.

Gotchas

Object keys and array lengths reflect the original input shape. A leaf value of "" is treated as missing when that leaf is loaded, but the parent container still reports its original keys or length.

Example (Providing config from a plain object)

import { Config, ConfigProvider, Effect } from "effect"

const provider = ConfigProvider.fromUnknown({
  database: {
    host: "localhost",
    port: 5432
  }
})

const host = Config.string("host").parse(
  provider.pipe(ConfigProvider.nested("database"))
)

// Effect.runSync(host) // "localhost"