Chainspec validation (#6197)

* chainspec validation

* better error formatting for chainspec

* lint validate_chainspecs.sh

* quit takes &str instead of S: AsRef<str>

* push CI

* don't double check spec validity

chainspec/src/main.rs

@@ -0,0 +1,48 @@
+extern crate serde_json;
+extern crate serde_ignored;
+extern crate ethjson;
+
+use std::collections::BTreeSet;
+use std::{fs, env, process};
+use ethjson::spec::Spec;
+
+fn quit(s: &str) -> ! {
+	println!("{}", s);
+	process::exit(1);
+}
+
+fn main() {
+	let mut args = env::args();
+	if args.len() != 2 {
+		quit("You need to specify chainspec.json\n\
+		\n\
+		./chainspec <chainspec.json>");
+	}
+
+	let path = args.nth(1).expect("args.len() == 2; qed");
+	let file = match fs::File::open(&path) {
+		Ok(file) => file,
+		Err(_) => quit(&format!("{} could not be opened", path)),
+	};
+
+	let mut unused = BTreeSet::new();
+	let mut deserializer = serde_json::Deserializer::from_reader(file);
+
+	let spec: Result<Spec, _> = serde_ignored::deserialize(&mut deserializer, |field| {
+		unused.insert(field.to_string());
+	});
+
+	if let Err(err) = spec {
+		quit(&format!("{} {}", path, err.to_string()));
+	}
+
+	if !unused.is_empty() {
+		let err = unused.into_iter()
+			.map(|field| format!("{} unexpected field `{}`", path, field))
+			.collect::<Vec<_>>()
+			.join("\n");
+		quit(&err);
+	}
+
+	println!("{} is valid", path);
+}