Fix error handling

- comment errors: ReturnCodes
- update mock ext implementation
- return Error::CodeNotFound when no code for such hash

frame/contracts/src/benchmarking/mod.rs

@@ -808,6 +808,7 @@ benchmarks! {
 		let origin = RawOrigin::Signed(instance.caller.clone());
 	}: call(origin, instance.addr, 0u32.into(), Weight::MAX, None, vec![])
 
+	#[skip_meta]
 	seal_set_code_hash {
 		let r in 0 .. API_BENCHMARK_BATCHES;
 		let code_hashes = (0..r * API_BENCHMARK_BATCH_SIZE)

frame/contracts/src/wasm/code_cache.rs

@@ -129,7 +129,7 @@ pub fn increment_refcount<T: Config>(code_hash: CodeHash<T>) -> Result<(), Dispa
 			info.refcount = info.refcount.saturating_add(1);
 			Ok(())
 		} else {
-			Err(DispatchError::CannotLookup)
+			Err(Error::<T>::CodeNotFound.into())
 		}
 	})
 }

frame/contracts/src/wasm/mod.rs

@@ -306,6 +306,7 @@ mod tests {
 	}
 
 	pub struct MockExt {
+		code_hashes: Vec<CodeHash<Test>>,
 		storage: HashMap<StorageKey, Vec<u8>>,
 		instantiates: Vec<InstantiateEntry>,
 		terminations: Vec<TerminationEntry>,
@@ -328,6 +329,7 @@ mod tests {
 	impl Default for MockExt {
 		fn default() -> Self {
 			Self {
+				code_hashes: Default::default(),
 				storage: Default::default(),
 				instantiates: Default::default(),
 				terminations: Default::default(),
@@ -410,7 +412,7 @@ mod tests {
 			Ok(result)
 		}
 		fn set_code_hash(&mut self, hash: CodeHash<Self::T>) -> Result<(), DispatchError> {
-			self.storage.insert(StorageKey::from(hash), vec![1, 2, 3]);
+			self.code_hashes.push(hash);
 			Ok(())
 		}
 		fn caller(&self) -> &AccountIdOf<Self::T> {
@@ -2225,7 +2227,7 @@ mod tests {
 		let mut mock_ext = MockExt::default();
 		execute(CODE, [0u8; 32].encode(), &mut mock_ext).unwrap();
 
-		assert_eq!(mock_ext.storage.get(&[17u8; 32]), Some(&vec![1, 2, 3]));
+		assert_eq!(mock_ext.code_hashes.pop().unwrap(), H256::from_slice(&[17u8; 32]));
 	}
 
 	#[test]

frame/contracts/src/wasm/runtime.rs

@@ -826,14 +826,17 @@ define_env!(Env, <E: Ext>,
 	//
 	// # Errors
 	//
-	// - requested buffer is not within the bounds of the sandbox memory.
-	// - the buffer contents cannot be decoded as the required type.
-	// - code for specified hash does not exist
+	// `ReturnCode::CodeNotFound`
 	[__unstable__] seal_set_code_hash(ctx, code_hash_ptr: u32) -> ReturnCode => {
 		ctx.charge_gas(RuntimeCosts::SetCodeHash)?;
 		let code_hash: CodeHash<<E as Ext>::T> = ctx.read_sandbox_memory_as(code_hash_ptr)?;
-		ctx.ext.set_code_hash(code_hash)?;
-		Ok(ReturnCode::Success)
+		match ctx.ext.set_code_hash(code_hash) {
+			Err(err) =>	{
+				let code = Runtime::<E>::err_into_return_code(err)?;
+				Ok(code)
+			},
+			Ok(()) => Ok(ReturnCode::Success)
+		}
 	},
 
 	// Set the value at the given key in the contract storage.