[light/jsonrpc] Provide the actual account for `eth_coinbase` RPC and unify error handeling for light and full client (#9383)

* Provide the actual `account` for eth_coinbase

The previous implementation always provided the `zero address` on
`eth_coinbase` RPC. Now, instead the actual address is returned on
success or an error when no account(s) is found!

* full client `eth_coinbase` return err

In the full-client return an error when no account is found instead of
returning the `zero address`

* Remove needless blocks on single import

* Remove needless `static` lifetime on const

* Fix `rpc_eth_author` test

rpc/src/v1/impls/eth.rs

@@ -33,7 +33,7 @@ use ethcore::log_entry::LogEntry;
 use ethcore::miner::{self, MinerService};
 use ethcore::snapshot::SnapshotService;
 use ethcore::encoded;
-use sync::{SyncProvider};
+use sync::SyncProvider;
 use miner::external::ExternalMinerService;
 use transaction::{SignedTransaction, LocalizedTransaction};
 
@@ -52,7 +52,7 @@ use v1::types::{
 };
 use v1::metadata::Metadata;
 
-const EXTRA_INFO_PROOF: &'static str = "Object exists in blockchain (fetched earlier), extra_info is always available if object exists; qed";
+const EXTRA_INFO_PROOF: &str = "Object exists in blockchain (fetched earlier), extra_info is always available if object exists; qed";
 
 /// Eth RPC options
 pub struct EthClientOptions {
@@ -500,12 +500,16 @@ impl<C, SN: ?Sized, S: ?Sized, M, EM, T: StateInfo + 'static> Eth for EthClient<
 	}
 
 	fn author(&self) -> Result<RpcH160> {
-		let mut miner = self.miner.authoring_params().author;
+		let miner = self.miner.authoring_params().author;
 		if miner == 0.into() {
-			miner = self.accounts.accounts().ok().and_then(|a| a.get(0).cloned()).unwrap_or_default();
+			self.accounts.accounts()
+				.ok()
+				.and_then(|a| a.first().cloned())
+				.map(From::from)
+				.ok_or_else(|| errors::account("No accounts were found", ""))
+		} else {
+			Ok(RpcH160::from(miner))
 		}
-
-		Ok(RpcH160::from(miner))
 	}
 
 	fn is_mining(&self) -> Result<bool> {

rpc/src/v1/impls/light/eth.rs

@@ -252,7 +252,11 @@ impl<T: LightChainClient + 'static> Eth for EthClient<T> {
 	}
 
 	fn author(&self) -> Result<RpcH160> {
-		Ok(Default::default())
+		self.accounts.accounts()
+			.ok()
+			.and_then(|a| a.first().cloned())
+			.map(From::from)
+			.ok_or_else(|| errors::account("No accounts were found", ""))
 	}
 
 	fn is_mining(&self) -> Result<bool> {

rpc/src/v1/tests/mocked/eth.rs

@@ -359,25 +359,27 @@ fn rpc_eth_author() {
 	let make_res = |addr| r#"{"jsonrpc":"2.0","result":""#.to_owned() + &format!("0x{:x}", addr) + r#"","id":1}"#;
 	let tester = EthTester::default();
 
-	let req = r#"{
+	let request = r#"{
 		"jsonrpc": "2.0",
 		"method": "eth_coinbase",
 		"params": [],
 		"id": 1
 	}"#;
 
-	// No accounts - returns zero
-	assert_eq!(tester.io.handle_request_sync(req), Some(make_res(Address::zero())));
+	let response = r#"{"jsonrpc":"2.0","error":{"code":-32023,"message":"No accounts were found","data":"\"\""},"id":1}"#;
+
+	// No accounts - returns an error indicating that no accounts were found
+	assert_eq!(tester.io.handle_request_sync(request), Some(response.to_string()));
 
 	// Account set - return first account
 	let addr = tester.accounts_provider.new_account(&"123".into()).unwrap();
-	assert_eq!(tester.io.handle_request_sync(req), Some(make_res(addr)));
+	assert_eq!(tester.io.handle_request_sync(request), Some(make_res(addr)));
 
 	for i in 0..20 {
 		let addr = tester.accounts_provider.new_account(&format!("{}", i).into()).unwrap();
 		tester.miner.set_author(addr.clone(), None).unwrap();
 
-		assert_eq!(tester.io.handle_request_sync(req), Some(make_res(addr)));
+		assert_eq!(tester.io.handle_request_sync(request), Some(make_res(addr)));
 	}
 }