RPC errors & logs (#1845)

* Refactoring errors in RPC

* Updating jsonrpc-core

* Fixing code_at

* Avoid mentioning obvious segments in proof

[ci:skip]

ethcore/src/client/client.rs

@@ -784,8 +784,8 @@ impl BlockChainClient for Client {
 		Self::block_hash(&self.chain, id)
 	}
 
-	fn code(&self, address: &Address) -> Option<Bytes> {
-		self.state().code(address)
+	fn code(&self, address: &Address, id: BlockID) -> Option<Option<Bytes>> {
+		self.state_at(id).map(|s| s.code(address))
 	}
 
 	fn balance(&self, address: &Address, id: BlockID) -> Option<U256> {

ethcore/src/client/test_client.rs

@@ -319,8 +319,11 @@ impl BlockChainClient for TestBlockChainClient {
 		self.nonce(address, BlockID::Latest).unwrap()
 	}
 
-	fn code(&self, address: &Address) -> Option<Bytes> {
-		self.code.read().get(address).cloned()
+	fn code(&self, address: &Address, id: BlockID) -> Option<Option<Bytes>> {
+		match id {
+			BlockID::Latest => Some(self.code.read().get(address).cloned()),
+			_ => None,
+		}
 	}
 
 	fn balance(&self, address: &Address, id: BlockID) -> Option<U256> {

ethcore/src/client/traits.rs

@@ -81,8 +81,14 @@ pub trait BlockChainClient : Sync + Send {
 	/// Get block hash.
 	fn block_hash(&self, id: BlockID) -> Option<H256>;
 
-	/// Get address code.
-	fn code(&self, address: &Address) -> Option<Bytes>;
+	/// Get address code at given block's state.
+	fn code(&self, address: &Address, id: BlockID) -> Option<Option<Bytes>>;
+
+	/// Get address code at the latest block's state.
+	fn latest_code(&self, address: &Address) -> Option<Bytes> {
+		self.code(address, BlockID::Latest)
+			.expect("code will return Some if given BlockID::Latest; qed")
+	}
 
 	/// Get address balance at the given block's state.
 	///

ethcore/src/miner/miner.rs

@@ -528,7 +528,7 @@ impl MinerService for Miner {
 
 	fn code(&self, chain: &MiningBlockChainClient, address: &Address) -> Option<Bytes> {
 		let sealing_work = self.sealing_work.lock();
-		sealing_work.queue.peek_last_ref().map_or_else(|| chain.code(address), |b| b.block().fields().state.code(address))
+		sealing_work.queue.peek_last_ref().map_or_else(|| chain.latest_code(address), |b| b.block().fields().state.code(address))
 	}
 
 	fn set_author(&self, author: Address) {