[pallet-revive] allow delegate calls to non-contract accounts (#7729)

This PR changes the behavior of delegate calls when the callee is not a
contract account: Instead of returning a `CodeNotFound` error, this is
allowed and the caller observes a successful call with empty output.

The change makes for example the following contract behave the same as
on EVM:

```Solidity
contract DelegateCall {
    function delegateToLibrary() external returns (bool) {
        address testAddress = 0x0000000000000000000000000000000000000000;
        (bool success, ) = testAddress.delegatecall(
            abi.encodeWithSignature("test()")
        );
        return success;
    }
}
```

Closes paritytech/revive#235

---------

Signed-off-by: xermicus <[email protected]>
Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: xermicus

prdoc/pr_7729.prdoc

@@ -0,0 +1,24 @@
+title: '[pallet-revive] allow delegate calls to non-contract accounts'
+doc:
+- audience: Runtime Dev
+  description: |-
+    This PR changes the behavior of delegate calls when the callee is not a contract account: Instead of returning a `CodeNotFound` error, this is allowed and the caller observes a successful call with empty output.
+
+    The change makes for example the following contract behave the same as on EVM:
+
+    ```Solidity
+    contract DelegateCall {
+        function delegateToLibrary() external returns (bool) {
+            address testAddress = 0x0000000000000000000000000000000000000000;
+            (bool success, ) = testAddress.delegatecall(
+                abi.encodeWithSignature("test()")
+            );
+            return success;
+        }
+    }
+    ```
+
+    Closes https://github.com/paritytech/revive/issues/235
+crates:
+- name: pallet-revive
+  bump: major

substrate/frame/revive/src/exec.rs

@@ -1575,10 +1575,9 @@ where
 		// This is for example the case for unknown code hashes or creating the frame fails.
 		*self.last_frame_output_mut() = Default::default();
 
-		let code_hash = ContractInfoOf::<T>::get(&address)
-			.ok_or(Error::<T>::CodeNotFound)
-			.map(|c| c.code_hash)?;
-		let executable = E::from_storage(code_hash, self.gas_meter_mut())?;
+		// Delegate-calls to non-contract accounts are considered success.
+		let Some(info) = ContractInfoOf::<T>::get(&address) else { return Ok(()) };
+		let executable = E::from_storage(info.code_hash, self.gas_meter_mut())?;
 		let top_frame = self.top_frame_mut();
 		let contract_info = top_frame.contract_info().clone();
 		let account_id = top_frame.account_id.clone();

substrate/frame/revive/src/exec/tests.rs

@@ -33,7 +33,7 @@ use crate::{
 	AddressMapper, Error,
 };
 use assert_matches::assert_matches;
-use frame_support::{assert_err, assert_noop, assert_ok, parameter_types};
+use frame_support::{assert_err, assert_ok, parameter_types};
 use frame_system::{AccountInfo, EventRecord, Phase};
 use pallet_revive_uapi::ReturnFlags;
 use pretty_assertions::assert_eq;
@@ -376,19 +376,16 @@ fn delegate_call_missing_contract() {
 		let origin = Origin::from_account_id(ALICE);
 		let mut storage_meter = storage::meter::Meter::new(&origin, 0, 55).unwrap();
 
-		// contract code missing
-		assert_noop!(
-			MockStack::run_call(
-				origin.clone(),
-				BOB_ADDR,
-				&mut GasMeter::<Test>::new(GAS_LIMIT),
-				&mut storage_meter,
-				U256::zero(),
-				vec![],
-				false,
-			),
-			ExecError { error: Error::<Test>::CodeNotFound.into(), origin: ErrorOrigin::Callee }
-		);
+		// contract code missing should still succeed to mimic EVM behavior.
+		assert_ok!(MockStack::run_call(
+			origin.clone(),
+			BOB_ADDR,
+			&mut GasMeter::<Test>::new(GAS_LIMIT),
+			&mut storage_meter,
+			U256::zero(),
+			vec![],
+			false,
+		));
 
 		// add missing contract code
 		place_contract(&CHARLIE, missing_ch);
@@ -2631,17 +2628,14 @@ fn last_frame_output_is_always_reset() {
 		);
 		assert_eq!(ctx.ext.last_frame_output(), &Default::default());
 
-		// An unknown code hash to fail the delegate_call on the first condition.
+		// An unknown code hash should succeed but clear the output.
 		*ctx.ext.last_frame_output_mut() = output_revert();
-		assert_eq!(
-			ctx.ext.delegate_call(
-				Weight::zero(),
-				U256::zero(),
-				H160([0xff; 20]),
-				Default::default()
-			),
-			Err(Error::<Test>::CodeNotFound.into())
-		);
+		assert_ok!(ctx.ext.delegate_call(
+			Weight::zero(),
+			U256::zero(),
+			H160([0xff; 20]),
+			Default::default()
+		));
 		assert_eq!(ctx.ext.last_frame_output(), &Default::default());
 
 		// An unknown code hash to fail instantiation on the first condition.