Support account_nextIndex RPC. (#460)

* Use node-rpc extensions to support account_nextIndex.

* Remove todo.

* Update lock.

* Use new srml_system_rpc crate.

* Update to substrate=master

* Update lockfile.

* Update to polkadot-master.

* Apply suggestions from code review

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

polkadot/rpc/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "polkadot-rpc"
+version = "0.6.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2018"
+
+[dependencies]
+client = { package = "substrate-client", git = "https://github.com/paritytech/substrate", branch = "polkadot-master" }
+jsonrpc-core = "13.2.0"
+polkadot-primitives = { path = "../primitives" }
+sr-primitives = { git = "https://github.com/paritytech/substrate", branch = "polkadot-master"  }
+substrate-rpc = { git = "https://github.com/paritytech/substrate", branch = "polkadot-master" }
+transaction_pool = { package = "substrate-transaction-pool", git = "https://github.com/paritytech/substrate", branch = "polkadot-master"  }
+srml-system-rpc = { git = "https://github.com/paritytech/substrate", branch = "polkadot-master"  }
+

polkadot/rpc/src/lib.rs

@@ -0,0 +1,45 @@
+// Copyright 2019 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot 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.
+
+// Polkadot 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 Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Polkadot-specific RPCs implementation.
+
+#![warn(missing_docs)]
+
+use std::sync::Arc;
+
+use polkadot_primitives::{Block, AccountId, Nonce};
+use sr_primitives::traits::ProvideRuntimeApi;
+use transaction_pool::txpool::{ChainApi, Pool};
+
+/// A type representing all RPC extensions.
+pub type RpcExtension = jsonrpc_core::IoHandler<substrate_rpc::Metadata>;
+
+/// Instantiate all RPC extensions.
+pub fn create<C, P>(client: Arc<C>, pool: Arc<Pool<P>>) -> RpcExtension where
+	C: ProvideRuntimeApi,
+	C: client::blockchain::HeaderBackend<Block>,
+	C: Send + Sync + 'static,
+	C::Api: srml_system_rpc::AccountNonceApi<Block, AccountId, Nonce>,
+	P: ChainApi + Sync + Send + 'static,
+{
+	use srml_system_rpc::{System, SystemApi};
+
+	let mut io = jsonrpc_core::IoHandler::default();
+	io.extend_with(
+		SystemApi::to_delegate(System::new(client.clone(), pool))
+	);
+	io
+}