ChainSpec trait (#5185)

* ChainSpec trait

* Apply suggestions from code review

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* Added docs

* Fixed build

* Fixed build

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/bin/node-template/node/src/chain_spec.rs

@@ -12,7 +12,7 @@ use sp_runtime::traits::{Verify, IdentifyAccount};
 //const STAGING_TELEMETRY_URL: &str = "wss://telemetry.polkadot.io/submit/";
 
 /// Specialized `ChainSpec`. This is a specialization of the general Substrate ChainSpec type.
-pub type ChainSpec = sc_service::ChainSpec<GenesisConfig>;
+pub type ChainSpec = sc_service::GenericChainSpec<GenesisConfig>;
 
 /// The chain specification option. This is expected to come in from the CLI and
 /// is little more than one of a number of alternatives which can easily be converted
@@ -142,9 +142,9 @@ fn testnet_genesis(initial_authorities: Vec<(AuraId, GrandpaId)>,
 	}
 }
 
-pub fn load_spec(id: &str) -> Result<Option<ChainSpec>, String> {
+pub fn load_spec(id: &str) -> Result<Box<dyn sc_service::ChainSpec>, String> {
 	Ok(match Alternative::from(id) {
-		Some(spec) => Some(spec.load()?),
-		None => None,
+		Some(spec) => Box::new(spec.load()?),
+		None => Box::new(ChainSpec::from_json_file(std::path::PathBuf::from(id))?),
 	})
 }

substrate/bin/node-template/node/src/service.rs

@@ -4,7 +4,7 @@ use std::sync::Arc;
 use std::time::Duration;
 use sc_client::LongestChain;
 use sc_client_api::ExecutorProvider;
-use node_template_runtime::{self, GenesisConfig, opaque::Block, RuntimeApi};
+use node_template_runtime::{self, opaque::Block, RuntimeApi};
 use sc_service::{error::{Error as ServiceError}, AbstractService, Configuration, ServiceBuilder};
 use sp_inherents::InherentDataProviders;
 use sc_executor::native_executor_instance;
@@ -69,7 +69,7 @@ macro_rules! new_full_start {
 }
 
 /// Builds a new service for a full client.
-pub fn new_full(config: Configuration<GenesisConfig>)
+pub fn new_full(config: Configuration)
 	-> Result<impl AbstractService, ServiceError>
 {
 	let is_authority = config.roles.is_authority();
@@ -181,7 +181,7 @@ pub fn new_full(config: Configuration<GenesisConfig>)
 }
 
 /// Builds a new service for a light client.
-pub fn new_light(config: Configuration<GenesisConfig>)
+pub fn new_light(config: Configuration)
 	-> Result<impl AbstractService, ServiceError>
 {
 	let inherent_data_providers = InherentDataProviders::new();