Repository: paritytech/substrate
File: primitives/genesis-builder/src/lib.rs (Rust)

Code before:
	/// API to interact with GenesisConfig for the runtime
	pub trait GenesisBuilder {
		/// Get the default `GenesisConfig` as a JSON blob.
		///
		/// This function instantiates the default `GenesisConfig` struct for the runtime and serializes it into a JSON
		/// blob. It returns a `Vec<u8>` containing the JSON representation of the default `GenesisConfig`.
		fn get_default_as_json() -> sp_std::vec::Vec<u8>;

		/// Patch default `GenesisConfig` using given JSON patch and store it in the storage.
		///
		/// This function generates the `GenesisConfig` for the runtime by applying a provided JSON patch.
		/// The patch modifies the default `GenesisConfig` allowing customization of the specific keys.
		/// The resulting `GenesisConfig` is then deserialized from the patched JSON representation and
		/// stored in the storage.
		///
		/// If the provided JSON patch is incorrect or the deserialization fails the error will be returned.
		/// Method may panic if creation of json representation of default config fails.
		///
		/// The patching process modifies the default `GenesisConfig` according to the following rules:
		/// 1. Existing keys in the default configuration will be overridden by the corresponding values in the patch.
		/// 2. If a key exists in the patch but not in the default configuration, it will be added to the resulting `GenesisConfig`.
		/// 3. Keys in the default configuration that have null values in the patch will be removed from the resulting
		///    `GenesisConfig`. This is helpful for changing enum variant value.
		///
		/// Please note that the patch may contain full `GenesisConfig`.
		fn build_config(patch: sp_std::vec::Vec<u8>) -> Result;

		/// Build `GenesisConfig` from a JSON blob not using any defaults and store it in the storage.
		///
		/// This function deserializes the full `GenesisConfig` from the given JSON blob and puts it into the storage.
		/// If the provided JSON blob is incorrect or incomplete or the deserialization fails, an error is returned.
		/// It is recommended to log any errors encountered during the process.
		///
		/// Please note that provided json blob must contain all `GenesisConfig` fields, no defaults will be used.
		fn build_config_no_defaults(json: sp_std::vec::Vec<u8>) -> Result;
	}
}


Review comment (suggestion):
```suggestion
		fn patch_default_config(patch: sp_std::vec::Vec<u8>) -> sp_std::result::Result<sp_std::vec::Vec<u8>, RuntimeString>;
```

Code after:
// This file is part of Substrate.

// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// 	http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#![cfg_attr(not(feature = "std"), no_std)]

//! Substrate genesis config builder
//!
//! This Runtime API allows to construct `GenesisConfig`, in particular:
//! - serialize the runtime default `GenesisConfig` struct into json format,
//! - put the GenesisConfig struct into the storage. Internally this operation calls
//!   `GenesisBuild::build` function for all runtime pallets, which is typically provided by
//!   pallet's author.
//! - deserialize the `GenesisConfig` from given json blob and put `GenesisConfig` into the state
//!   storage. Allows to build customized configuration.
//!
//! Providing externalities with empty storage and putting `GenesisConfig` into storage allows to
//! catch and build the raw storage of `GenesisConfig` which is the foundation for genesis block.

/// The result type alias, used in build methods. `Err` contains formatted error message.
pub type Result = core::result::Result<(), sp_runtime::RuntimeString>;

sp_api::decl_runtime_apis! {
	/// API to interact with GenesisConfig for the runtime
	pub trait GenesisBuilder {
		/// Creates the default `GenesisConfig` and returns it as a JSON blob.
		///
		/// This function instantiates the default `GenesisConfig` struct for the runtime and serializes it into a JSON
		/// blob. It returns a `Vec<u8>` containing the JSON representation of the default `GenesisConfig`.
		fn create_default_config() -> sp_std::vec::Vec<u8>;

		/// Build `GenesisConfig` from a JSON blob not using any defaults and store it in the storage.
		///
		/// This function deserializes the full `GenesisConfig` from the given JSON blob and puts it into the storage.
		/// If the provided JSON blob is incorrect or incomplete or the deserialization fails, an error is returned.
		/// It is recommended to log any errors encountered during the process.
		///
		/// Please note that provided json blob must contain all `GenesisConfig` fields, no defaults will be used.
		fn build_config(json: sp_std::vec::Vec<u8>) -> Result;
	}
}