Improve some RPC error messages. (#6311)

rpc/src/v1/impls/eth_pubsub.rs

@@ -245,17 +245,27 @@ impl<C: Send + Sync + 'static> EthPubSub for EthPubSubClient<C> {
 		kind: pubsub::Kind,
 		params: Trailing<pubsub::Params>,
 	) {
-		match (kind, params.into()) {
+		let error = match (kind, params.into()) {
 			(pubsub::Kind::NewHeads, None) => {
-				self.heads_subscribers.write().push(subscriber)
+				self.heads_subscribers.write().push(subscriber);
+				return;
 			},
 			(pubsub::Kind::Logs, Some(pubsub::Params::Logs(filter))) => {
 				self.logs_subscribers.write().push(subscriber, filter.into());
+				return;
+			},
+			(pubsub::Kind::NewHeads, _) => {
+				errors::invalid_params("newHeads", "Expected no parameters.")
+			},
+			(pubsub::Kind::Logs, _) => {
+				errors::invalid_params("logs", "Expected a filter object.")
 			},
 			_ => {
-				let _ = subscriber.reject(errors::unimplemented(None));
+				errors::unimplemented(None)
 			},
-		}
+		};
+
+		let _ = subscriber.reject(error);
 	}
 
 	fn unsubscribe(&self, id: SubscriptionId) -> BoxFuture<bool, Error> {

rpc/src/v1/types/block.rs

@@ -214,7 +214,7 @@ impl<T: Serialize> Serialize for Rich<T> {
 			// and serialize
 			value.serialize(serializer)
 		} else {
-			Err(S::Error::custom("Unserializable structures."))
+			Err(S::Error::custom("Unserializable structures: expected objects"))
 		}
 	}
 }

rpc/src/v1/types/block_number.rs

@@ -79,8 +79,12 @@ impl<'a> Visitor<'a> for BlockNumberVisitor {
 			"latest" => Ok(BlockNumber::Latest),
 			"earliest" => Ok(BlockNumber::Earliest),
 			"pending" => Ok(BlockNumber::Pending),
-			_ if value.starts_with("0x") => u64::from_str_radix(&value[2..], 16).map(BlockNumber::Num).map_err(|_| Error::custom("invalid block number")),
+			_ if value.starts_with("0x") => u64::from_str_radix(&value[2..], 16).map(BlockNumber::Num).map_err(|e| {
-			_ => value.parse::<u64>().map(BlockNumber::Num).map_err(|_| Error::custom("invalid block number"))
+				Error::custom(format!("Invalid block number: {}", e))
+			}),
+			_ => value.parse::<u64>().map(BlockNumber::Num).map_err(|e| {
+				Error::custom(format!("Invalid block number: {}", e))
+			}),
 		}
 	}
 

rpc/src/v1/types/bytes.rs

@@ -81,9 +81,9 @@ impl<'a> Visitor<'a> for BytesVisitor {
 			);
 			Ok(Bytes::new(Vec::new()))
 		} else if value.len() >= 2 && &value[0..2] == "0x" && value.len() & 1 == 0 {
-			Ok(Bytes::new(FromHex::from_hex(&value[2..]).map_err(|_| Error::custom("invalid hex"))?))
+			Ok(Bytes::new(FromHex::from_hex(&value[2..]).map_err(|e| Error::custom(format!("Invalid hex: {}", e)))?))
 		} else {
-			Err(Error::custom("invalid format"))
+			Err(Error::custom("Invalid bytes format. Expected a 0x-prefixed hex string with even length"))
 		}
 	}
 

rpc/src/v1/types/derivation.rs

@@ -121,7 +121,7 @@ impl<'a> Visitor<'a> for DerivationTypeVisitor {
 		match value {
 			"soft" => Ok(DerivationType::Soft),
 			"hard" => Ok(DerivationType::Hard),
-			_ => Err(Error::custom("invalid derivation type")),
+			v => Err(Error::custom(format!("invalid derivation type: {:?}", v))),
 		}
 	}
 

rpc/src/v1/types/filter.rs

@@ -43,7 +43,7 @@ impl<'a, T> Deserialize<'a> for VariadicValue<T> where T: DeserializeOwned {
 
 		from_value(v.clone()).map(VariadicValue::Single)
 			.or_else(|_| from_value(v).map(VariadicValue::Multiple))
-			.map_err(|_| D::Error::custom("Invalid type."))
+			.map_err(|err| D::Error::custom(format!("Invalid variadic value type: {}", err)))
 	}
 }
 

rpc/src/v1/types/index.rs

@@ -47,8 +47,12 @@ impl<'a> Visitor<'a> for IndexVisitor {
 
 	fn visit_str<E>(self, value: &str) -> Result<Self::Value, E> where E: Error {
 		match value {
-			_ if value.starts_with("0x") => usize::from_str_radix(&value[2..], 16).map(Index).map_err(|_| Error::custom("invalid index")),
+			_ if value.starts_with("0x") => usize::from_str_radix(&value[2..], 16).map(Index).map_err(|e| {
-			_ => value.parse::<usize>().map(Index).map_err(|_| Error::custom("invalid index")),
+				Error::custom(format!("Invalid index: {}", e))
+			}),
+			_ => value.parse::<usize>().map(Index).map_err(|e| {
+				Error::custom(format!("Invalid index: {}", e))
+			}),
 		}
 	}
 

rpc/src/v1/types/pubsub.rs

@@ -84,7 +84,7 @@ impl<'a> Deserialize<'a> for Params {
 		}
 
 		from_value(v.clone()).map(Params::Logs)
-			.map_err(|_| D::Error::custom("Invalid type."))
+			.map_err(|e| D::Error::custom(format!("Invalid Pub-Sub parameters: {}", e)))
 	}
 }