base on ⚙️ Layered configuration system for Rust applications (with strong support for 12-factor applications). # config-rs > Layered configuration system for Rust applications (with strong support for [12-factor] applications). [](https://docs.rs/config)  [](https://crates.io/crates/config) [12-factor]: https://12factor.net/config - Set defaults - Set explicit values (to programmatically override) - Read from [JSON], [TOML], [YAML], [INI], [RON], [JSON5], [CORN] files - Read from environment - Loosely typed — Configuration values may be read in any supported type, as long as there exists a reasonable conversion - Access nested fields using a formatted path — Uses a subset of JSONPath; currently supports the child ( `redis.port` ) and subscript operators ( `databases[0].name` ) [JSON]: https://github.com/serde-rs/json [TOML]: https://github.com/toml-lang/toml [YAML]: https://github.com/Ethiraric/yaml-rust2 [INI]: https://github.com/zonyitoo/rust-ini [RON]: https://github.com/ron-rs/ron [JSON5]: https://github.com/callum-oakley/json5-rs [CORN]: https://cornlang.dev/ Please note that this library can not be used to write changed configuration values back to the configuration file(s)! ## Usage ### Feature flags - `ini` - Adds support for reading INI files - `json` - Adds support for reading JSON files - `yaml` - Adds support for reading YAML files - `toml` - Adds support for reading TOML files - `ron` - Adds support for reading RON files - `json5` - Adds support for reading JSON5 files - `corn` - Adds support for reading Corn files ### Support for custom formats Library provides out of the box support for most renowned data formats such as JSON or Yaml. Nonetheless, it contains an extensibility point - a `Format` trait that, once implemented, allows seamless integration with library's APIs using custom, less popular or proprietary data formats. See [custom_file_format](https://github.com/rust-cli/config-rs/tree/main/examples/custom_file_format) example for more information. ### More See the [documentation](https://docs.rs/config) or [examples](https://github.com/rust-cli/config-rs/tree/main/examples) for more usage information. ## License Licensed under either of * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or <https://www.apache.org/licenses/LICENSE-2.0>) * MIT license ([LICENSE-MIT](LICENSE-MIT) or <https://opensource.org/license/mit>) at your option. ", Assign "at most 3 tags" to the expected json: {"id":"12351","tags":[]} "only from the tags list I provide: []" returns me the "expected json"