[balances] fix balance entry serde hack

README.md

@@ -24,3 +24,19 @@ a registry for classifieds from community members, linking to IPFS
 
 ## personhood-oracle
 a digital personhood verification oracle with XCM support. See pallet sybil-gate-example for how to use this from another parachain
+
+## Dev Hints
+* There is a know issue with serializing u-/i128 in the json-rpc crate, see (https://github.com/paritytech/substrate/issues/4641). 
+This affects us predominantly when serializing fixed point numbers in the custom RPCs. There is a custom serialization
+shim as a workaround for that issue in [ep-core](./primitives/core), which can be used as custom serde attribute like:
+
+```rust
+#[cfg_attr(feature = "serde_derive", derive(Serialize, Deserialize))]
+pub struct BalanceEntry<BlockNumber> {
+	/// The balance of the account after last manual adjustment
+	#[cfg_attr(feature = "serde_derive", serde(with = "serialize_fixed"))]
+	pub principal: BalanceType,
+	/// The time (block height) at which the balance was last adjusted
+	pub last_update: BlockNumber,
+}
+```

balances/rpc/src/lib.rs

@@ -14,6 +14,8 @@
 // You should have received a copy of the GNU General Public License
 // along with Encointer.  If not, see <http://www.gnu.org/licenses/>.
 
+use encointer_balances_rpc_runtime_api::BalancesApi as BalancesRuntimeApi;
+use encointer_primitives::{balances::BalanceEntry, communities::CommunityIdentifier};
 use jsonrpc_core::{Error, ErrorCode, Result};
 use jsonrpc_derive::rpc;
 use sc_rpc::DenyUnsafe;
@@ -25,9 +27,6 @@ use sp_runtime::{
 };
 use std::sync::Arc;
 
-use encointer_balances_rpc_runtime_api::BalancesApi as BalancesRuntimeApi;
-use encointer_primitives::communities::CommunityIdentifier;
-
 #[rpc]
 pub trait BalancesApi<BlockHash, AccountId, BlockNumber>
 where
@@ -39,7 +38,7 @@ where
 		&self,
 		account: AccountId,
 		at: Option<BlockHash>,
-	) -> Result<Vec<(CommunityIdentifier, Vec<u8>)>>;
+	) -> Result<Vec<(CommunityIdentifier, BalanceEntry<BlockNumber>)>>;
 }
 
 pub struct Balances<Client, Block, AccountId> {
@@ -70,19 +69,12 @@ where
 		&self,
 		account: AccountId,
 		at: Option<<Block as BlockT>::Hash>,
-	) -> Result<Vec<(CommunityIdentifier, Vec<u8>)>> {
+	) -> Result<Vec<(CommunityIdentifier, BalanceEntry<BlockNumberFor<Block>>)>> {
 		self.deny_unsafe.check_if_safe()?;
 
 		let api = self.client.runtime_api();
 		let at = BlockId::hash(at.unwrap_or_else(|| self.client.info().best_hash));
-		return Ok(api
-			.get_all_balances(&at, &account)
-			.map_err(runtime_error_into_rpc_err)?
-			.iter()
-			// serde can't cope with i128 and panics. So we need to hand-encode the value here
-			// see https://github.com/paritytech/substrate/issues/4641
-			.map(|b| (b.0, b.1.encode()))
-			.collect())
+		return Ok(api.get_all_balances(&at, &account).map_err(runtime_error_into_rpc_err)?)
 	}
 }
 

primitives/src/balances.rs

@@ -22,6 +22,9 @@ use sp_core::RuntimeDebug;
 #[cfg(feature = "serde_derive")]
 use serde::{Deserialize, Serialize};
 
+#[cfg(feature = "serde_derive")]
+use ep_core::serde::serialize_fixed;
+
 // We're working with fixpoint here.
 pub type BalanceType = I64F64;
 pub type Demurrage = I64F64;
@@ -32,6 +35,7 @@ pub type Demurrage = I64F64;
 #[cfg_attr(feature = "serde_derive", derive(Serialize, Deserialize))]
 pub struct BalanceEntry<BlockNumber> {
 	/// The balance of the account after last manual adjustment
+	#[cfg_attr(feature = "serde_derive", serde(with = "serialize_fixed"))]
 	pub principal: BalanceType,
 	/// The time (block height) at which the balance was last adjusted
 	pub last_update: BlockNumber,