returning errors with extra fields in config file (#3663)

parity/cli/config.invalid3.toml

@@ -0,0 +1,3 @@
+[signer]
+passwd = []
+

parity/cli/mod.rs

@@ -649,11 +649,12 @@ mod tests {
 	fn should_parse_config_and_return_errors() {
 		let config1 = Args::parse_config(include_str!("./config.invalid1.toml"));
 		let config2 = Args::parse_config(include_str!("./config.invalid2.toml"));
+		let config3 = Args::parse_config(include_str!("./config.invalid3.toml"));
 
-		match (config1, config2) {
-			(Err(ArgsError::Parsing(_)), Err(ArgsError::Decode(_))) => {},
-			(a, b) => {
-				assert!(false, "Got invalid error types: {:?}, {:?}", a, b);
+		match (config1, config2, config3) {
+			(Err(ArgsError::Parsing(_)), Err(ArgsError::Decode(_)), Err(ArgsError::UnknownFields(_))) => {},
+			(a, b, c) => {
+				assert!(false, "Got invalid error types: {:?}, {:?}, {:?}", a, b, c);
 			}
 		}
 	}

parity/cli/usage.rs

@@ -58,6 +58,7 @@ macro_rules! usage {
 			Parsing(Vec<toml::ParserError>),
 			Decode(toml::DecodeError),
 			Config(String, io::Error),
+			UnknownFields(String),
 		}
 
 		impl ArgsError {
@@ -80,6 +81,11 @@ macro_rules! usage {
 						println_stderr!("There was an error reading your config file at: {}", path);
 						println_stderr!("{}", e);
 						process::exit(2)
+					},
+					ArgsError::UnknownFields(fields) => {
+						println_stderr!("You have some extra fields in your config file:");
+						println_stderr!("{}", fields);
+						process::exit(2)
 					}
 				}
 			}
@@ -173,10 +179,13 @@ macro_rules! usage {
 				let mut value_parser = toml::Parser::new(&config);
 				match value_parser.parse() {
 					Some(value) => {
-						let result = rustc_serialize::Decodable::decode(&mut toml::Decoder::new(toml::Value::Table(value)));
-						match result {
-							Ok(config) => Ok(config),
-							Err(e) => Err(e.into()),
+						let mut decoder = toml::Decoder::new(toml::Value::Table(value));
+						let result = rustc_serialize::Decodable::decode(&mut decoder);
+
+						match (result, decoder.toml) {
+							(Err(e), _) => Err(e.into()),
+							(_, Some(toml)) => Err(ArgsError::UnknownFields(toml::encode_str(&toml))),
+							(Ok(config), None) => Ok(config),
 						}
 					},
 					None => Err(ArgsError::Parsing(value_parser.errors)),