Improve mock_impl_runtime_apis! (#7370)

* Improve `mock_impl_runtime_apis!`

This adds a new attribute for functions being implemented in the
`mock_impl_runtime_apis!` macro, the `advanced` attribute. When this
attribute is given the user gets access to the `at` parameter and is
able to return a `Result`, instead of letting the macro generate this
stuff.

* Use the `at_param_name` directly

* Prevent clashing of `params`

substrate/primitives/api/test/tests/decl_and_impl.rs

@@ -19,9 +19,8 @@ use sp_api::{
 	RuntimeApiInfo, decl_runtime_apis, impl_runtime_apis, mock_impl_runtime_apis,
 	ApiExt,
 };
-
 use sp_runtime::{traits::{GetNodeBlockType, Block as BlockT}, generic::BlockId};
-
+use sp_core::NativeOrEncoded;
 use substrate_test_runtime_client::runtime::Block;
 use sp_blockchain::Result;
 
@@ -103,9 +102,20 @@ mock_impl_runtime_apis! {
 			unimplemented!()
 		}
 
-		fn same_name() {}
+		#[advanced]
+		fn same_name(_: &BlockId<Block>) -> std::result::Result<NativeOrEncoded<()>, String> {
+			Ok(().into())
+		}
 
-		fn wild_card(_: u32) {}
+		#[advanced]
+		fn wild_card(at: &BlockId<Block>, _: u32) -> std::result::Result<NativeOrEncoded<()>, String> {
+			if let BlockId::Number(1337) = at {
+				// yeah
+				Ok(().into())
+			} else {
+				Err("Ohh noooo".into())
+			}
+		}
 	}
 
 	impl ApiWithCustomVersion<Block> for MockApi {
@@ -180,3 +190,12 @@ fn mock_runtime_api_panics_on_calling_old_version() {
 	#[allow(deprecated)]
 	let _ = mock.same_name_before_version_2(&BlockId::Number(0));
 }
+
+#[test]
+fn mock_runtime_api_works_with_advanced() {
+	let mock = MockApi { block: None };
+
+	Api::<Block>::same_name(&mock, &BlockId::Number(0)).unwrap();
+	mock.wild_card(&BlockId::Number(1337), 1).unwrap();
+	assert_eq!(String::from("Ohh noooo"), mock.wild_card(&BlockId::Number(1336), 1).unwrap_err());
+}