Crate sc_chain_spec

Substrate chain configurations.

This crate contains structs and utilities to declare a runtime-specific configuration file (a.k.a chain spec).

Basic chain spec type containing all required parameters is ChainSpec. It can be extended with additional options that contain configuration specific to your chain. Usually the extension is going to be an amalgamate of types exposed by Substrate core modules. To allow the core modules to retrieve their configuration from your extension you should use ChainSpecExtension macro exposed by this crate.

use std::collections::HashMap;
use sc_chain_spec::{GenericChainSpec, ChainSpecExtension};

#[derive(Clone, Debug, serde::Serialize, serde::Deserialize, ChainSpecExtension)]
pub struct MyExtension {
	pub known_blocks: HashMap<u64, String>,
}

pub type MyChainSpec<G> = GenericChainSpec<G, MyExtension>;

Some parameters may require different values depending on the current blockchain height (a.k.a. forks). You can use ChainSpecGroup macro and provided Forks structure to put such parameters to your chain spec. This will allow to override a single parameter starting at specific block number.

use sc_chain_spec::{Forks, ChainSpecGroup, ChainSpecExtension, GenericChainSpec};

#[derive(Clone, Debug, serde::Serialize, serde::Deserialize, ChainSpecGroup)]
pub struct ClientParams {
	max_block_size: usize,
	max_extrinsic_size: usize,
}

#[derive(Clone, Debug, serde::Serialize, serde::Deserialize, ChainSpecGroup)]
pub struct PoolParams {
	max_transaction_size: usize,
}

#[derive(Clone, Debug, serde::Serialize, serde::Deserialize, ChainSpecGroup, ChainSpecExtension)]
pub struct Extension {
	pub client: ClientParams,
	pub pool: PoolParams,
}

pub type BlockNumber = u64;

/// A chain spec supporting forkable `ClientParams`.
pub type MyChainSpec1<G> = GenericChainSpec<G, Forks<BlockNumber, ClientParams>>;

/// A chain spec supporting forkable `Extension`.
pub type MyChainSpec2<G> = GenericChainSpec<G, Forks<BlockNumber, Extension>>;

It’s also possible to have a set of parameters that is allowed to change with block numbers (i.e. is forkable), and another set that is not subject to changes. This is also possible by declaring an extension that contains Forks within it.

use serde::{Serialize, Deserialize};
use sc_chain_spec::{Forks, GenericChainSpec, ChainSpecGroup, ChainSpecExtension};

#[derive(Clone, Debug, Serialize, Deserialize, ChainSpecGroup)]
pub struct ClientParams {
	max_block_size: usize,
	max_extrinsic_size: usize,
}

#[derive(Clone, Debug, Serialize, Deserialize, ChainSpecGroup)]
pub struct PoolParams {
	max_transaction_size: usize,
}

#[derive(Clone, Debug, Serialize, Deserialize, ChainSpecExtension)]
pub struct Extension {
	pub client: ClientParams,
	#[forks]
	pub pool: Forks<u64, PoolParams>,
}

pub type MyChainSpec<G> = GenericChainSpec<G, Extension>;

Structs

Forks
GenericChainSpec	A configuration of a chain. Can be used to build a genesis block.
LightSyncState	Hardcoded infomation that allows light clients to sync quickly.
SerializableLightSyncState	The serializable form of LightSyncState. Created using LightSyncState::serialize.

Enums

ChainType

The type of a chain.

Traits

ChainSpec	Common interface of a chain specification.
Extension	A collection of ChainSpec extensions.
Fork	A ChainSpec extension fork definition.
GetExtension	A subset if the Extension trait that only allows for quering extensions.
Group	A ChainSpec extension.
RuntimeGenesis	A set of traits for the runtime genesis config.

Functions

get_extension

Helper function that queries an extension by type from GetExtension trait object.

Type Definitions

NoExtension	A type denoting empty extensions.
Properties	Arbitrary properties defined in chain spec as a JSON object

Derive Macros

ChainSpecExtension
ChainSpecGroup