config-rs

Combines defaults, file settings, environment variables, and programmatic overrides into a unified hierarchy, adhering to 12-factor principles for environment-aware apps.

Supports reading from JSON, TOML, YAML, INI, RON, JSON5, and Corn files via feature flags, allowing diverse configuration sources without lock-in.

Uses JSONPath-like syntax with child and subscript operators (e.g., `redis.port` or `databases[0].name`) to simplify accessing complex configuration structures.

Provides a `Format` trait for integrating custom or proprietary data formats, as shown in the repository's examples, ensuring adaptability to niche use cases.