Add tests & Service's Configuration has optional fields that shouldn't be optional (#4842)

Related to #4776 
Related to https://github.com/paritytech/polkadot/pull/832

To summarize the changes:
1. I did not manage to validate with types the service's Configuration. But I did reduce the possibility of errors by moving all the "fill" functions to their respective structopts
2. I split params.rs to multiple modules: one module params for just CLI parameters and one module commands for CLI subcommands (and RunCmd). Every command and params are in their own file so things are grouped better together and easier to remove
3. I removed the run and run_subcommand helpers as they are not helping much anymore. Running a command is always a set of 3 commands: 1. init 2. update config 3. run. This still allow the user to change the config before arguments get parsed or right after.
4. I added tests for all subcommands.
5. [deleted]

Overall the aim is to improve the situation with the Configuration and the optional parameters, add tests, make the API more consistent and simpler.

substrate/client/cli/src/commands/mod.rs

@@ -0,0 +1,145 @@
+// Copyright 2018-2020 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+mod runcmd;
+mod export_blocks_cmd;
+mod build_spec_cmd;
+mod import_blocks_cmd;
+mod check_block_cmd;
+mod revert_cmd;
+mod purge_chain_cmd;
+
+use std::fmt::Debug;
+use structopt::StructOpt;
+
+use sc_service::{
+	Configuration, ChainSpecExtension, RuntimeGenesis, ServiceBuilderCommand, ChainSpec,
+};
+use sp_runtime::traits::{Block as BlockT, Header as HeaderT};
+
+use crate::error;
+use crate::VersionInfo;
+use crate::params::SharedParams;
+
+pub use crate::commands::runcmd::RunCmd;
+pub use crate::commands::export_blocks_cmd::ExportBlocksCmd;
+pub use crate::commands::build_spec_cmd::BuildSpecCmd;
+pub use crate::commands::import_blocks_cmd::ImportBlocksCmd;
+pub use crate::commands::check_block_cmd::CheckBlockCmd;
+pub use crate::commands::revert_cmd::RevertCmd;
+pub use crate::commands::purge_chain_cmd::PurgeChainCmd;
+
+/// default sub directory to store network config
+const DEFAULT_NETWORK_CONFIG_PATH : &'static str = "network";
+
+/// All core commands that are provided by default.
+///
+/// The core commands are split into multiple subcommands and `Run` is the default subcommand. From
+/// the CLI user perspective, it is not visible that `Run` is a subcommand. So, all parameters of
+/// `Run` are exported as main executable parameters.
+#[derive(Debug, Clone, StructOpt)]
+pub enum Subcommand {
+	/// Build a spec.json file, outputing to stdout.
+	BuildSpec(build_spec_cmd::BuildSpecCmd),
+
+	/// Export blocks to a file.
+	ExportBlocks(export_blocks_cmd::ExportBlocksCmd),
+
+	/// Import blocks from file.
+	ImportBlocks(import_blocks_cmd::ImportBlocksCmd),
+
+	/// Validate a single block.
+	CheckBlock(check_block_cmd::CheckBlockCmd),
+
+	/// Revert chain to the previous state.
+	Revert(revert_cmd::RevertCmd),
+
+	/// Remove the whole chain data.
+	PurgeChain(purge_chain_cmd::PurgeChainCmd),
+}
+
+impl Subcommand {
+	/// Get the shared parameters of a `CoreParams` command
+	pub fn get_shared_params(&self) -> &SharedParams {
+		use Subcommand::*;
+
+		match self {
+			BuildSpec(params) => &params.shared_params,
+			ExportBlocks(params) => &params.shared_params,
+			ImportBlocks(params) => &params.shared_params,
+			CheckBlock(params) => &params.shared_params,
+			Revert(params) => &params.shared_params,
+			PurgeChain(params) => &params.shared_params,
+		}
+	}
+
+	/// Run any `CoreParams` command
+	pub fn run<G, E, B, BC, BB>(
+		self,
+		config: Configuration<G, E>,
+		builder: B,
+	) -> error::Result<()>
+	where
+		B: FnOnce(Configuration<G, E>) -> Result<BC, sc_service::error::Error>,
+		G: RuntimeGenesis,
+		E: ChainSpecExtension,
+		BC: ServiceBuilderCommand<Block = BB> + Unpin,
+		BB: sp_runtime::traits::Block + Debug,
+		<<<BB as BlockT>::Header as HeaderT>::Number as std::str::FromStr>::Err: std::fmt::Debug,
+		<BB as BlockT>::Hash: std::str::FromStr,
+	{
+		match self {
+			Subcommand::BuildSpec(cmd) => cmd.run(config),
+			Subcommand::ExportBlocks(cmd) => cmd.run(config, builder),
+			Subcommand::ImportBlocks(cmd) => cmd.run(config, builder),
+			Subcommand::CheckBlock(cmd) => cmd.run(config, builder),
+			Subcommand::PurgeChain(cmd) => cmd.run(config),
+			Subcommand::Revert(cmd) => cmd.run(config, builder),
+		}
+	}
+
+	/// Update and prepare a `Configuration` with command line parameters
+	pub fn update_config<G, E, F>(
+		&self,
+		mut config: &mut Configuration<G, E>,
+		spec_factory: F,
+		version: &VersionInfo,
+	) -> error::Result<()> where
+		G: RuntimeGenesis,
+		E: ChainSpecExtension,
+		F: FnOnce(&str) -> Result<Option<ChainSpec<G, E>>, String>,
+	{
+		match self {
+			Subcommand::BuildSpec(cmd) => cmd.update_config(&mut config, spec_factory, version),
+			Subcommand::ExportBlocks(cmd) => cmd.update_config(&mut config, spec_factory, version),
+			Subcommand::ImportBlocks(cmd) => cmd.update_config(&mut config, spec_factory, version),
+			Subcommand::CheckBlock(cmd) => cmd.update_config(&mut config, spec_factory, version),
+			Subcommand::PurgeChain(cmd) => cmd.update_config(&mut config, spec_factory, version),
+			Subcommand::Revert(cmd) => cmd.update_config(&mut config, spec_factory, version),
+		}
+	}
+
+	/// Initialize substrate. This must be done only once.
+	///
+	/// This method:
+	///
+	/// 1. Set the panic handler
+	/// 2. Raise the FD limit
+	/// 3. Initialize the logger
+	pub fn init(&self, version: &VersionInfo) -> error::Result<()> {
+		self.get_shared_params().init(version)
+	}
+}