[contracts] Fixed the bug with transfer value for delegate call

frame/contracts/common/src/lib.rs

@@ -116,6 +116,8 @@ bitflags! {
 	#[cfg_attr(feature = "std", derive(Serialize, Deserialize))]
 	#[cfg_attr(feature = "std", serde(rename_all = "camelCase", transparent))]
 	pub struct ReturnFlags: u32 {
+		/// If all bits are zero it is successful case.
+		const SUCCESS = 0x0;
 		/// If this bit is set all changes made by the contract execution are rolled back.
 		const REVERT = 0x0000_0001;
 	}

frame/contracts/src/exec.rs

@@ -797,8 +797,10 @@ where
 				)?;
 			}
 
-			// Every call or instantiate also optionally transferres balance.
-			self.initial_transfer()?;
+			// Every non delegate call or instantiate also optionally transfers the balance.
+			if self.top_frame().delegate_caller.is_none() {
+				self.initial_transfer()?;
+			}
 
 			// Call into the wasm blob.
 			let output = executable
@@ -1560,6 +1562,82 @@ mod tests {
 		});
 	}
 
+	#[test]
+	fn correct_transfer_on_call() {
+		let origin = ALICE;
+		let dest = BOB;
+		let value = 55;
+
+		let success_ch = MockLoader::insert(Call, move |ctx, _| {
+			assert_eq!(ctx.ext.value_transferred(), value);
+			Ok(ExecReturnValue { flags: ReturnFlags::SUCCESS, data: Bytes(Vec::new()) })
+		});
+
+		ExtBuilder::default().build().execute_with(|| {
+			let schedule = <Test as Config>::Schedule::get();
+			place_contract(&dest, success_ch);
+			set_balance(&origin, 100);
+			let balance = get_balance(&dest);
+			let mut storage_meter = storage::meter::Meter::new(&origin, Some(0), 55).unwrap();
+
+			let _ = MockStack::run_call(
+				origin.clone(),
+				dest.clone(),
+				&mut GasMeter::<Test>::new(GAS_LIMIT),
+				&mut storage_meter,
+				&schedule,
+				value,
+				vec![],
+				None,
+			)
+				.unwrap();
+
+			assert_eq!(get_balance(&origin), 100 - value);
+			assert_eq!(get_balance(&dest), balance + value);
+		});
+	}
+
+	#[test]
+	fn correct_transfer_on_delegate_call() {
+		let origin = ALICE;
+		let dest = BOB;
+		let value = 35;
+
+		let success_ch = MockLoader::insert(Call, move |ctx, _| {
+			assert_eq!(ctx.ext.value_transferred(), value);
+			Ok(ExecReturnValue { flags: ReturnFlags::SUCCESS, data: Bytes(Vec::new()) })
+		});
+
+		let delegate_ch = MockLoader::insert(Call, move |ctx, _| {
+			assert_eq!(ctx.ext.value_transferred(), value);
+			let _ = ctx.ext.delegate_call(success_ch, Vec::new())?;
+			Ok(ExecReturnValue { flags: ReturnFlags::SUCCESS, data: Bytes(Vec::new()) })
+		});
+
+		ExtBuilder::default().build().execute_with(|| {
+			let schedule = <Test as Config>::Schedule::get();
+			place_contract(&dest, delegate_ch);
+			set_balance(&origin, 100);
+			let balance = get_balance(&dest);
+			let mut storage_meter = storage::meter::Meter::new(&origin, Some(0), 55).unwrap();
+
+			let _ = MockStack::run_call(
+				origin.clone(),
+				dest.clone(),
+				&mut GasMeter::<Test>::new(GAS_LIMIT),
+				&mut storage_meter,
+				&schedule,
+				value,
+				vec![],
+				None,
+			)
+				.unwrap();
+
+			assert_eq!(get_balance(&origin), 100 - value);
+			assert_eq!(get_balance(&dest), balance + value);
+		});
+	}
+
 	#[test]
 	fn changes_are_reverted_on_failing_call() {
 		// This test verifies that changes are reverted on a call which fails (or equally, returns