ChainSpec extensions (#3692)

* Add some chainspec tests and make sure we validate it.

* Manual implementation of Extension + Forks definitions.

* Move chain spec to separate crate.

* Allow using ChainSpec with extensions.

* Renames.

* Implement Extension derive.

* Implement Extension for Forks.

* Support specifying fork blocks.

* make for_blocks work

* Support forks correctly.

* Add a bunch of docs.

* Make fork blocks optional.

* Add missing docs.

* Fix build.

* Use struct for check_block params.

* Fix tests?

* Clean up.

substrate/core/chain-spec/derive/src/lib.rs

@@ -0,0 +1,39 @@
+// Copyright 2019 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Macros to derive chain spec extension traits implementation.
+
+extern crate proc_macro;
+
+mod impls;
+
+use proc_macro::TokenStream;
+
+#[proc_macro_derive(ChainSpecGroup)]
+pub fn group_derive(input: TokenStream) -> TokenStream {
+	match syn::parse(input) {
+		Ok(ast) => impls::group_derive(&ast),
+		Err(e) => e.to_compile_error().into(),
+	}
+}
+
+#[proc_macro_derive(ChainSpecExtension, attributes(forks))]
+pub fn extensions_derive(input: TokenStream) -> TokenStream {
+	match syn::parse(input) {
+		Ok(ast) => impls::extension_derive(&ast),
+		Err(e) => e.to_compile_error().into(),
+	}
+}