RPC to query transaction fee + weight + info (#3876)

* initial version for testing

* New version that compiles

* optional at block parameter

* Fix some more view grumbles.

* Update srml/transaction-payment/src/lib.rs

substrate/srml/transaction-payment/rpc/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "srml-transaction-payment-rpc"
+version = "2.0.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2018"
+
+[dependencies]
+client = { package = "substrate-client", path = "../../../core/client" }
+codec = { package = "parity-scale-codec", version = "1.0.0" }
+jsonrpc-core = "13.2.0"
+jsonrpc-core-client = "13.2.0"
+jsonrpc-derive = "13.2.0"
+primitives = { package = "substrate-primitives",  path = "../../../core/primitives" }
+rpc-primitives = { package = "substrate-rpc-primitives", path = "../../../core/rpc/primitives" }
+serde = { version = "1.0.101", features = ["derive"] }
+sr-primitives = { path = "../../../core/sr-primitives" }
+srml-transaction-payment-rpc-runtime-api = { path = "./runtime-api" }

substrate/srml/transaction-payment/rpc/runtime-api/Cargo.toml

@@ -0,0 +1,22 @@
+[package]
+name = "srml-transaction-payment-rpc-runtime-api"
+version = "2.0.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2018"
+
+[dependencies]
+serde = { version = "1.0.101", optional = true, features = ["derive"] }
+client = { package = "substrate-client", path = "../../../../core/client", default-features = false }
+codec = { package = "parity-scale-codec", version = "1.0.6", default-features = false, features = ["derive"] }
+rstd = { package = "sr-std", path = "../../../../core/sr-std", default-features = false }
+sr-primitives = { path = "../../../../core/sr-primitives", default-features = false }
+
+[features]
+default = ["std"]
+std = [
+	"serde",
+	"client/std",
+	"codec/std",
+	"rstd/std",
+	"sr-primitives/std",
+]

substrate/srml/transaction-payment/rpc/runtime-api/src/lib.rs

@@ -0,0 +1,47 @@
+// Copyright 2019 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/>.
+
+//! Runtime API definition for transaction payment module.
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+use rstd::prelude::*;
+use sr_primitives::weights::{Weight, DispatchClass};
+use codec::{Encode, Codec, Decode};
+#[cfg(feature = "std")]
+use serde::{Serialize, Deserialize};
+
+/// Some information related to a dispatchable that can be queried from the runtime.
+#[derive(Eq, PartialEq, Encode, Decode, Default)]
+#[cfg_attr(feature = "std", derive(Debug, Serialize, Deserialize))]
+pub struct RuntimeDispatchInfo<Balance> {
+	/// Weight of this dispatch.
+	pub weight: Weight,
+	/// Class of this dispatch.
+	pub class: DispatchClass,
+	/// The partial inclusion fee of this dispatch. This does not include tip or anything else which
+	/// is dependent on the signature (aka. depends on a `SignedExtension`).
+	pub partial_fee: Balance,
+}
+
+client::decl_runtime_apis! {
+	pub trait TransactionPaymentApi<Balance, Extrinsic> where
+		Balance: Codec,
+		Extrinsic: Codec,
+	{
+		fn query_info(uxt: Extrinsic, len: u32) -> RuntimeDispatchInfo<Balance>;
+	}
+}

substrate/srml/transaction-payment/rpc/src/lib.rs

@@ -0,0 +1,108 @@
+// Copyright 2019 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/>.
+
+//! RPC interface for the transaction payment module.
+
+use std::sync::Arc;
+use codec::{Codec, Decode};
+use client::blockchain::HeaderBackend;
+use jsonrpc_core::{Error as RpcError, ErrorCode, Result};
+use jsonrpc_derive::rpc;
+use sr_primitives::{
+	generic::BlockId,
+	traits::{Block as BlockT, ProvideRuntimeApi},
+};
+use primitives::Bytes;
+use srml_transaction_payment_rpc_runtime_api::RuntimeDispatchInfo;
+pub use srml_transaction_payment_rpc_runtime_api::TransactionPaymentApi as TransactionPaymentRuntimeApi;
+pub use self::gen_client::Client as TransactionPaymentClient;
+
+#[rpc]
+pub trait TransactionPaymentApi<BlockHash, Balance> {
+	#[rpc(name = "payment_queryInfo")]
+	fn query_info(
+		&self,
+		encoded_xt: Bytes,
+		at: Option<BlockHash>
+	) -> Result<RuntimeDispatchInfo<Balance>>;
+}
+
+/// A struct that implements the [`TransactionPaymentApi`].
+pub struct TransactionPayment<C, P> {
+	client: Arc<C>,
+	_marker: std::marker::PhantomData<P>,
+}
+
+impl<C, P> TransactionPayment<C, P> {
+	/// Create new `TransactionPayment` with the given reference to the client.
+	pub fn new(client: Arc<C>) -> Self {
+		TransactionPayment { client, _marker: Default::default() }
+	}
+}
+
+/// Error type of this RPC api.
+pub enum Error {
+	/// The transaction was not decodable.
+	DecodeError,
+	/// The call to runtime failed.
+	RuntimeError,
+}
+
+impl From<Error> for i64 {
+	fn from(e: Error) -> i64 {
+		match e {
+			Error::RuntimeError => 1,
+			Error::DecodeError => 2,
+		}
+	}
+}
+
+impl<C, Block, Balance, Extrinsic> TransactionPaymentApi<<Block as BlockT>::Hash, Balance>
+	for TransactionPayment<C, (Block, Extrinsic)>
+where
+	Block: BlockT,
+	C: Send + Sync + 'static,
+	C: ProvideRuntimeApi,
+	C: HeaderBackend<Block>,
+	C::Api: TransactionPaymentRuntimeApi<Block, Balance, Extrinsic>,
+	Balance: Codec,
+	Extrinsic: Codec + Send + Sync + 'static,
+{
+	fn query_info(
+		&self,
+		encoded_xt: Bytes,
+		at: Option<<Block as BlockT>::Hash>
+	) -> Result<RuntimeDispatchInfo<Balance>> {
+		let api = self.client.runtime_api();
+		let at = BlockId::hash(at.unwrap_or_else(||
+			// If the block hash is not supplied assume the best block.
+			self.client.info().best_hash
+		));
+
+		let encoded_len = encoded_xt.len() as u32;
+
+		let uxt: Extrinsic = Decode::decode(&mut &*encoded_xt).map_err(|e| RpcError {
+			code: ErrorCode::ServerError(Error::DecodeError.into()),
+			message: "Unable to query dispatch info.".into(),
+			data: Some(format!("{:?}", e).into()),
+		})?;
+		api.query_info(&at, uxt, encoded_len).map_err(|e| RpcError {
+			code: ErrorCode::ServerError(Error::RuntimeError.into()),
+			message: "Unable to query dispatch info.".into(),
+			data: Some(format!("{:?}", e).into()),
+		})
+	}
+}