Errors & warnings for inappropriate RPCs (#6029)

* Clarify function name

Function checks if sealing is currently underway, not to be confused
with checking whether the engine performs internal sealing.

* Error when work called on internal sealing engine

* Error submitting work for internal sealing engine

* Fix inverted bool and style grumbles

* Add can_produce_work_package to TestMinerService

* Error when setting engine signer on PoW chain

* Unit tests for engine signing

Setting engine signer should fail if chain does not seal internally
or client lacks account provider.

* Tweak TestMinerService

* Fix minor style grumbles

ethcore/src/account_provider/mod.rs

@@ -64,7 +64,9 @@ pub enum SignError {
 	/// Low-level hardware device error.
 	Hardware(HardwareError),
 	/// Low-level error from store
-	SStore(SSError)
+	SStore(SSError),
+	/// Inappropriate chain
+	InappropriateChain,
 }
 
 impl fmt::Display for SignError {
@@ -74,6 +76,7 @@ impl fmt::Display for SignError {
 			SignError::NotFound => write!(f, "Account does not exist"),
 			SignError::Hardware(ref e) => write!(f, "{}", e),
 			SignError::SStore(ref e) => write!(f, "{}", e),
+			SignError::InappropriateChain => write!(f, "Inappropriate chain"),
 		}
 	}
 }

ethcore/src/miner/miner.rs

@@ -804,9 +804,15 @@ impl MinerService for Miner {
 				// | Make sure to release the locks before calling that method.             |
 				// --------------------------------------------------------------------------
 				self.engine.set_signer(ap.clone(), address, password);
+				Ok(())
+			} else {
+				warn!(target: "miner", "No account provider");
+				Err(AccountError::NotFound)
 			}
+		} else {
+			warn!(target: "miner", "Cannot set engine signer on a PoW chain.");
+			Err(AccountError::InappropriateChain)
 		}
-		Ok(())
 	}
 
 	fn set_extra_data(&self, extra_data: Bytes) {
@@ -1085,6 +1091,10 @@ impl MinerService for Miner {
 		self.transaction_queue.read().last_nonce(address)
 	}
 
+	fn can_produce_work_package(&self) -> bool {
+		self.engine.seals_internally().is_none()
+	}
+
 	/// Update sealing if required.
 	/// Prepare the block and work if the Engine does not seal internally.
 	fn update_sealing(&self, chain: &MiningBlockChainClient) {
@@ -1113,7 +1123,7 @@ impl MinerService for Miner {
 		}
 	}
 
-	fn is_sealing(&self) -> bool {
+	fn is_currently_sealing(&self) -> bool {
 		self.sealing_work.lock().queue.is_in_use()
 	}
 
@@ -1272,7 +1282,7 @@ mod tests {
 	use header::BlockNumber;
 	use types::transaction::{SignedTransaction, Transaction, PendingTransaction, Action};
 	use spec::Spec;
-	use tests::helpers::{generate_dummy_client};
+	use tests::helpers::{generate_dummy_client, generate_dummy_client_with_spec_and_accounts};
 
 	#[test]
 	fn should_prepare_block_to_seal() {
@@ -1440,4 +1450,22 @@ mod tests {
 		assert!(miner.pending_block().is_none());
 		assert_eq!(client.chain_info().best_block_number, 4 as BlockNumber);
 	}
+
+	#[test]
+	fn should_fail_setting_engine_signer_on_pow() {
+		let spec = Spec::new_pow_test_spec;
+		let tap = Arc::new(AccountProvider::transient_provider());
+		let addr = tap.insert_account("1".sha3().into(), "").unwrap();
+		let client = generate_dummy_client_with_spec_and_accounts(spec, Some(tap.clone()));
+		assert!(match client.miner().set_engine_signer(addr, "".into()) { Err(AccountError::InappropriateChain) => true, _ => false })
+	}
+
+	#[test]
+	fn should_fail_setting_engine_signer_without_account_provider() {
+		let spec = Spec::new_instant;
+		let tap = Arc::new(AccountProvider::transient_provider());
+		let addr = tap.insert_account("1".sha3().into(), "").unwrap();
+		let client = generate_dummy_client_with_spec_and_accounts(spec, None);
+		assert!(match client.miner().set_engine_signer(addr, "".into()) { Err(AccountError::NotFound) => true, _ => false });
+	}
 }

ethcore/src/miner/mod.rs

@@ -136,6 +136,9 @@ pub trait MinerService : Send + Sync {
 	/// Called when blocks are imported to chain, updates transactions queue.
 	fn chain_new_blocks(&self, chain: &MiningBlockChainClient, imported: &[H256], invalid: &[H256], enacted: &[H256], retracted: &[H256]);
 
+	/// PoW chain - can produce work package
+	fn can_produce_work_package(&self) -> bool;
+
 	/// New chain head event. Restart mining operation.
 	fn update_sealing(&self, chain: &MiningBlockChainClient);
 
@@ -176,7 +179,7 @@ pub trait MinerService : Send + Sync {
 	fn last_nonce(&self, address: &Address) -> Option<U256>;
 
 	/// Is it currently sealing?
-	fn is_sealing(&self) -> bool;
+	fn is_currently_sealing(&self) -> bool;
 
 	/// Suggested gas price.
 	fn sensible_gas_price(&self) -> U256;

ethcore/src/spec/spec.rs

@@ -451,6 +451,9 @@ impl Spec {
 	/// Create a new Spec with BasicAuthority which uses multiple validator sets changing with height.
 	/// Account with secrets "0".sha3() is the validator for block 1 and with "1".sha3() onwards.
 	pub fn new_validator_multi() -> Self { load_bundled!("validator_multi") }
+
+	/// Create a new spec for a PoW chain
+	pub fn new_pow_test_spec() -> Self { load_bundled!("ethereum/olympic") }
 }
 
 #[cfg(test)]