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/executive/src/lib.rs

@@ -571,7 +571,7 @@ mod tests {
 			assert!(Executive::apply_extrinsic(x2.clone()).unwrap().is_ok());
 
 			// default weight for `TestXt` == encoded length.
-			assert_eq!(<system::Module<Runtime>>::all_extrinsics_weight(), (3 * len).into());
+			assert_eq!(<system::Module<Runtime>>::all_extrinsics_weight(), (3 * len) as u32);
 			assert_eq!(<system::Module<Runtime>>::all_extrinsics_len(), 3 * len);
 
 			let _ = <system::Module<Runtime>>::finalize();

substrate/srml/transaction-payment/Cargo.toml

@@ -10,6 +10,7 @@ rstd = { package = "sr-std", path = "../../core/sr-std", default-features = fals
 sr-primitives = { path = "../../core/sr-primitives", default-features = false }
 support = { package = "srml-support", path = "../support", default-features = false }
 system = { package = "srml-system", path = "../system", default-features = false }
+transaction-payment-rpc-runtime-api = { package = "srml-transaction-payment-rpc-runtime-api", path = "./rpc/runtime-api", default-features = false }
 
 [dev-dependencies]
 runtime-io = { package = "sr-io", path = "../../core/sr-io" }
@@ -24,4 +25,5 @@ std = [
 	"sr-primitives/std",
 	"support/std",
 	"system/std",
+	"transaction-payment-rpc-runtime-api/std"
 ]

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()),
+		})
+	}
+}

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

@@ -44,8 +44,9 @@ use sr_primitives::{
 		TransactionValidity,
 	},
 	traits::{Zero, Saturating, SignedExtension, SaturatedConversion, Convert},
-	weights::{Weight, DispatchInfo},
+	weights::{Weight, DispatchInfo, GetDispatchInfo},
 };
+use transaction_payment_rpc_runtime_api::RuntimeDispatchInfo;
 
 type Multiplier = Fixed64;
 type BalanceOf<T> =
@@ -95,7 +96,33 @@ decl_module! {
 	}
 }
 
-impl<T: Trait> Module<T> {}
+impl<T: Trait> Module<T> {
+	/// Query the data that we know about the fee of a given `call`.
+	///
+	/// As this module is not and cannot be aware of the internals of a signed extension, it only
+	/// interprets them as some encoded value and takes their length into account.
+	///
+	/// All dispatchables must be annotated with weight and will have some fee info. This function
+	/// always returns.
+	// NOTE: we can actually make it understand `ChargeTransactionPayment`, but would be some hassle
+	// for sure. We have to make it aware of the index of `ChargeTransactionPayment` in `Extra`.
+	// Alternatively, we could actually execute the tx's per-dispatch and record the balance of the
+	// sender before and after the pipeline.. but this is way too much hassle for a very very little
+	// potential gain in the future.
+	pub fn query_info<Extrinsic: GetDispatchInfo>(
+		unchecked_extrinsic: Extrinsic,
+		len: u32,
+	) -> RuntimeDispatchInfo<BalanceOf<T>>
+		where T: Send + Sync,
+	{
+		let dispatch_info = <Extrinsic as GetDispatchInfo>::get_dispatch_info(&unchecked_extrinsic);
+
+		let partial_fee = <ChargeTransactionPayment<T>>::compute_fee(len, dispatch_info, 0u32.into());
+		let DispatchInfo { weight, class } = dispatch_info;
+
+		RuntimeDispatchInfo { weight, class, partial_fee }
+	}
+}
 
 /// Require the transactor pay for themselves and maybe include a tip to gain additional priority
 /// in the queue.
@@ -117,9 +144,9 @@ impl<T: Trait + Send + Sync> ChargeTransactionPayment<T> {
 	///      and the time it consumes.
 	///   - (optional) _tip_: if included in the transaction, it will be added on top. Only signed
 	///      transactions can have a tip.
-	fn compute_fee(len: usize, info: DispatchInfo, tip: BalanceOf<T>) -> BalanceOf<T> {
+	fn compute_fee(len: u32, info: DispatchInfo, tip: BalanceOf<T>) -> BalanceOf<T> {
 		let len_fee = if info.pay_length_fee() {
-			let len = <BalanceOf<T>>::from(len as u32);
+			let len = <BalanceOf<T>>::from(len);
 			let base = T::TransactionBaseFee::get();
 			let per_byte = T::TransactionByteFee::get();
 			base.saturating_add(per_byte.saturating_mul(len))
@@ -172,7 +199,7 @@ impl<T: Trait + Send + Sync> SignedExtension for ChargeTransactionPayment<T>
 	) -> TransactionValidity {
 		// pay any fees.
 		let tip = self.0;
-		let fee = Self::compute_fee(len, info, tip);
+		let fee = Self::compute_fee(len as u32, info, tip);
 		let imbalance = match T::Currency::withdraw(
 			who,
 			fee,
@@ -199,17 +226,27 @@ impl<T: Trait + Send + Sync> SignedExtension for ChargeTransactionPayment<T>
 #[cfg(test)]
 mod tests {
 	use super::*;
-	use support::{parameter_types, impl_outer_origin};
+	use codec::Encode;
+	use support::{parameter_types, impl_outer_origin, impl_outer_dispatch};
 	use primitives::H256;
 	use sr_primitives::{
 		Perbill,
-		testing::Header,
-		traits::{BlakeTwo256, IdentityLookup},
-		weights::DispatchClass,
+		testing::{Header, TestXt},
+		traits::{BlakeTwo256, IdentityLookup, Extrinsic},
+		weights::{DispatchClass, DispatchInfo, GetDispatchInfo},
 	};
+	use balances::Call as BalancesCall;
 	use rstd::cell::RefCell;
+	use transaction_payment_rpc_runtime_api::RuntimeDispatchInfo;
 
-	const CALL: &<Runtime as system::Trait>::Call = &();
+	const CALL: &<Runtime as system::Trait>::Call = &Call::Balances(BalancesCall::transfer(2, 69));
+
+	impl_outer_dispatch! {
+		pub enum Call for Runtime where origin: Origin {
+			balances::Balances,
+			system::System,
+		}
+	}
 
 	#[derive(Clone, PartialEq, Eq, Debug)]
 	pub struct Runtime;
@@ -229,7 +266,7 @@ mod tests {
 		type Origin = Origin;
 		type Index = u64;
 		type BlockNumber = u64;
-		type Call = ();
+		type Call = Call;
 		type Hash = H256;
 		type Hashing = BlakeTwo256;
 		type AccountId = u64;
@@ -294,6 +331,8 @@ mod tests {
 	}
 
 	type Balances = balances::Module<Runtime>;
+	type System = system::Module<Runtime>;
+	type TransactionPayment = Module<Runtime>;
 
 	pub struct ExtBuilder {
 		balance_factor: u64,
@@ -457,6 +496,39 @@ mod tests {
 			assert_eq!(Balances::free_balance(&1), 100 - 10 - (5 + 10 + 3) * 3 / 2);
 		})
 	}
+
+	#[test]
+	fn query_info_works() {
+		let call = Call::Balances(BalancesCall::transfer(2, 69));
+		let origin = 111111;
+		let extra = ();
+		let xt = TestXt::new(call, Some((origin, extra))).unwrap();
+		let info  = xt.get_dispatch_info();
+		let ext = xt.encode();
+		let len = ext.len() as u32;
+		ExtBuilder::default()
+			.fees(5, 1, 2)
+			.build()
+			.execute_with(||
+		{
+			// all fees should be x1.5
+			NextFeeMultiplier::put(Fixed64::from_rational(1, 2));
+
+			assert_eq!(
+				TransactionPayment::query_info(xt, len),
+				RuntimeDispatchInfo {
+					weight: info.weight,
+					class: info.class,
+					partial_fee: (
+						5 /* base */
+						+ len as u64 /* len * 1 */
+						+ info.weight.min(MaximumBlockWeight::get()) as u64 * 2 /* weight * weight_to_fee */
+					) * 3 / 2
+				},
+			);
+
+		});
+	}
 }