Make API backwards compatible with CC (#1697)

* Rework how a runtime api calls into the runtime

Now we generate a default implementation for each api call that calls
a generated method `method_runtime_api_impl`. This newly generated
method is the one that will be implemented by the `impl_runtime_apis`
macro in the runtime for the client side.

* Support `changed_in` to change runtime api function signatures

* Update documentation

* Fixes tests

* Implement checking the api version with a predicate

* Make the implementation backwards compatible with CC

* Update wasm files after merge

* Check for wasm runtime differences by building master and current branch

* Update spec_version and wasm files

* Fixes

* Revert my changes

* Remove `patch.crates-io` from test-runtime

substrate/core/client/src/block_builder/api.rs

@@ -16,13 +16,50 @@
 
 //! The runtime api for building blocks.
 
-use runtime_primitives::{traits::Block as BlockT, ApplyResult};
+use runtime_primitives::{traits::Block as BlockT, ApplyResult, RuntimeString};
 use rstd::vec::Vec;
 use sr_api_macros::decl_runtime_apis;
 pub use inherents::{InherentData, CheckInherentsResult};
+use parity_codec_derive::{Encode, Decode};
+
+/// The old representation of the inherent data.
+#[doc(hide)]
+#[derive(Encode, Decode)]
+pub struct OldInherentData {
+	/// Current timestamp.
+	pub timestamp: u64,
+	/// Blank report.
+	pub consensus: (),
+	/// Aura expected slot. Can take any value during block construction.
+	pub aura_expected_slot: u64,
+}
+
+impl OldInherentData {
+	/// Create a new `BasicInherentData` instance.
+	pub fn new(timestamp: u64, expected_slot: u64) -> Self {
+		Self {
+			timestamp,
+			consensus: (),
+			aura_expected_slot: expected_slot,
+		}
+	}
+}
+
+/// Error type used while checking inherents.
+#[doc(hide)]
+#[derive(Encode, PartialEq)]
+#[cfg_attr(feature = "std", derive(Decode))]
+pub enum OldCheckInherentError {
+	/// The inherents are generally valid but a delay until the given timestamp
+	/// is required.
+	ValidAtTimestamp(u64),
+	/// Some other error has occurred.
+	Other(RuntimeString),
+}
 
 decl_runtime_apis! {
 	/// The `BlockBuilder` api trait that provides required functions for building a block for a runtime.
+	#[api_version(2)]
 	pub trait BlockBuilder {
 		/// Apply the given extrinsics.
 		fn apply_extrinsic(extrinsic: <Block as BlockT>::Extrinsic) -> ApplyResult;
@@ -32,6 +69,11 @@ decl_runtime_apis! {
 		fn inherent_extrinsics(inherent: InherentData) -> Vec<<Block as BlockT>::Extrinsic>;
 		/// Check that the inherents are valid. The inherent data will vary from chain to chain.
 		fn check_inherents(block: Block, data: InherentData) -> CheckInherentsResult;
+		/// Check that the inherents are valid. The inherent data will vary from chain to chain.
+		///
+		/// Old version that is used by the CC network.
+		#[changed_in(2)]
+		fn check_inherents(block: Block, data: OldInherentData) -> ::std::result::Result<(), OldCheckInherentError>;
 		/// Generate a random seed.
 		fn random_seed() -> <Block as BlockT>::Hash;
 	}