Add an RPC method for calling a contract. (#3563)

* Sketch

* Some work on docs.

* Doc improvements.

* More docs.

* Some more docs.

* Yet another comment.

* Bump impl_version.

* Accept the block hash

* Use NumberOrHex

* Update node/rpc/src/contracts.rs

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* Move rpc/primitives

substrate/srml/contracts/src/exec.rs

@@ -75,11 +75,12 @@ pub type ExecResult = Result<ExecReturnValue, ExecError>;
 /// wrap the error string into an ExecutionError with the provided buffer and return from the
 /// enclosing function. This macro is used instead of .map_err(..)? in order to avoid taking
 /// ownership of buffer unless there is an error.
+#[macro_export]
 macro_rules! try_or_exec_error {
 	($e:expr, $buffer:expr) => {
 		match $e {
 			Ok(val) => val,
-			Err(reason) => return Err(ExecError { reason, buffer: $buffer }),
+			Err(reason) => return Err($crate::exec::ExecError { reason, buffer: $buffer }),
 		}
 	}
 }
@@ -191,15 +192,6 @@ pub trait Loader<T: Trait> {
 	fn load_main(&self, code_hash: &CodeHash<T>) -> Result<Self::Executable, &'static str>;
 }
 
-/// Struct that records a request to deposit an event with a list of topics.
-#[cfg_attr(any(feature = "std", test), derive(Debug, PartialEq, Eq))]
-pub struct IndexedEvent<T: Trait> {
-	/// A list of topics this event will be deposited with.
-	pub topics: Vec<T::Hash>,
-	/// The event to deposit.
-	pub event: Event<T>,
-}
-
 /// A trait that represent a virtual machine.
 ///
 /// You can view a virtual machine as something that takes code, an input data buffer,

substrate/srml/contracts/src/lib.rs

@@ -98,11 +98,13 @@ mod rent;
 #[cfg(test)]
 mod tests;
 
-use crate::exec::{ExecutionContext, ExecResult};
+use crate::exec::ExecutionContext;
 use crate::account_db::{AccountDb, DirectAccountDb};
-pub use crate::gas::{Gas, GasMeter};
 use crate::wasm::{WasmLoader, WasmVm};
 
+pub use crate::gas::{Gas, GasMeter};
+pub use crate::exec::{ExecResult, ExecReturnValue, ExecError, StatusCode};
+
 #[cfg(feature = "std")]
 use serde::{Serialize, Deserialize};
 use primitives::crypto::UncheckedFrom;
@@ -573,9 +575,9 @@ decl_module! {
 			let origin = ensure_signed(origin)?;
 			let dest = T::Lookup::lookup(dest)?;
 
-			Self::execute_wasm(origin, gas_limit, |ctx, gas_meter| {
-				ctx.call(dest, value, gas_meter, data)
-			})
+			Self::bare_call(origin, dest, value, gas_limit, data)
+				.map(|_| ())
+				.map_err(|e| e.reason)
 		}
 
 		/// Creates a new contract from the `codehash` generated by `put_code`, optionally transferring some balance.
@@ -601,6 +603,8 @@ decl_module! {
 				ctx.instantiate(endowment, gas_meter, &code_hash, data)
 					.map(|(_address, output)| output)
 			})
+			.map(|_| ())
+			.map_err(|e| e.reason)
 		}
 
 		/// Allows block producers to claim a small reward for evicting a contract. If a block producer
@@ -645,16 +649,37 @@ decl_module! {
 }
 
 impl<T: Trait> Module<T> {
+	/// Perform a call to a specified contract.
+	///
+	/// This function is similar to `Self::call`, but doesn't perform any lookups and better
+	/// suitable for calling directly from Rust.
+	pub fn bare_call(
+		origin: T::AccountId,
+		dest: T::AccountId,
+		value: BalanceOf<T>,
+		gas_limit: Gas,
+		input_data: Vec<u8>,
+	) -> ExecResult {
+		Self::execute_wasm(origin, gas_limit, |ctx, gas_meter| {
+			ctx.call(dest, value, gas_meter, input_data)
+		})
+	}
+
 	fn execute_wasm(
 		origin: T::AccountId,
 		gas_limit: Gas,
 		func: impl FnOnce(&mut ExecutionContext<T, WasmVm, WasmLoader>, &mut GasMeter<T>) -> ExecResult
-	) -> Result {
+	) -> ExecResult {
 		// Pay for the gas upfront.
 		//
 		// NOTE: it is very important to avoid any state changes before
 		// paying for the gas.
-		let (mut gas_meter, imbalance) = gas::buy_gas::<T>(&origin, gas_limit)?;
+		let (mut gas_meter, imbalance) =
+			try_or_exec_error!(
+				gas::buy_gas::<T>(&origin, gas_limit),
+				// We don't have a spare buffer here in the first place, so create a new empty one.
+				Vec::new()
+			);
 
 		let cfg = Config::preload();
 		let vm = WasmVm::new(&cfg.schedule);
@@ -705,8 +730,6 @@ impl<T: Trait> Module<T> {
 		});
 
 		result
-			.map(|_| ())
-			.map_err(|e| e.reason)
 	}
 
 	fn restore_to(