New sessions, kill consensus module (#2802)

* Draft of new sessions

* Reintroduce tuple impls

* Move staking module to new session API

* More work on staking and grandpa.

* Use iterator to avoid cloning and tuple macro

* Make runtime build again

* Polish the OpaqueKeys devex

* Move consensus logic into system & aura.

* Fix up system module

* Get build mostly going. Stuck at service.rs

* Building again

* Update srml/staking/src/lib.rs

Co-Authored-By: DemiMarie-parity <48690212+DemiMarie-parity@users.noreply.github.com>

* Refactoring out Consensus module, AuthorityIdOf, &c.

* Refactored out DigestItem::AuthoritiesChanged. Building.

* Remove tentative code

* Remove invalid comment

* Make Seal opaque and introduce nice methods for handling opaque items.

* Start to use proper digest for Aura authorities tracking.

* Fix up grandpa, remove system::Raw/Log

* Refactor Grandpa to use new logging infrastructure.

Also make authorityid/sessionkey static. Switch over to storing
authorities in a straight Vec.

* Building again

* Tidy up some AuthorityIds

* Expunge most of the rest of the AuthorityKey confusion.

Also, de-generify Babe and re-generify Aura.

* Remove cruft

* Untangle last of the `AuthorityId`s.

* Sort out finality_tracker

* Refactor median getting

* Apply suggestions from code review

Co-Authored-By: Robert Habermeier <rphmeier@gmail.com>

* Session tests works

* Update core/sr-primitives/src/generic/digest.rs

Co-Authored-By: DemiMarie-parity <48690212+DemiMarie-parity@users.noreply.github.com>

* Session tests works

* Fix for staking from @dvc94ch

* log an error

* fix test runtime build

* Some test fixes

* Staking mock update to new session api.

* Fix build.

* Move OpaqueKeys to primitives.

* Use on_initialize instead of check_rotate_session.

* Update tests to new staking api.

* fixup mock

* Fix bond_extra_and_withdraw_unbonded_works.

* Fix bond_with_little_staked_value_bounded_by_slot_stake.

* Fix bond_with_no_staked_value.

* Fix change_controller_works.

* Fix less_than_needed_candidates_works.

* Fix multi_era_reward_should_work.

* Fix nominating_and_rewards_should_work.

* Fix nominators_also_get_slashed.

* Fix phragmen_large_scale_test.

* Fix phragmen_poc_works.

* Fix phragmen_score_should_be_accurate_on_large_stakes.

* Fix phragmen_should_not_overflow.

* Fix reward_destination_works.

* Fix rewards_should_work.

* Fix sessions_and_eras_should_work.

* Fix slot_stake_is_least_staked_validator.

* Fix too_many_unbond_calls_should_not_work.

* Fix wrong_vote_is_null.

* Fix runtime.

* Fix wasm runtime build.

* Update Cargo.lock

* Fix warnings.

* Fix grandpa tests.

* Fix test-runtime build.

* Fix template node build.

* Fix stuff.

* Update Cargo.lock to fix CI

* Re-add missing AuRa logs

Runtimes are required to know about every digest they receive ― they
panic otherwise.  This re-adds support for AuRa pre-runtime digests.

* Update core/consensus/babe/src/digest.rs

Co-Authored-By: DemiMarie-parity <48690212+DemiMarie-parity@users.noreply.github.com>

* Kill log trait and all that jazz.

* Refactor staking tests.

* Fix ci runtime wasm check.

* Line length 120.

* Make tests build again

* Remove trailing commas in function declarations

The `extern_functions!` macro doesn’t like them, perhaps due to a bug in
rustc.

* Fix type error

* Fix compilation errors

* Fix a test

* Another couple of fixes

* Fix another test

* More test fixes

* Another test fix

* Bump runtime.

* Wrap long line

* Fix build, remove redundant code.

* Issue to track TODO

* Leave the benchmark code alone.

* Fix missing `std::time::{Instant, Duration}`

* Indentation

* Aura ConsensusLog as enum

substrate/core/consensus/aura/src/digest.rs

@@ -18,20 +18,22 @@
 //!
 //! This implements the digests for AuRa, to allow the private
 //! `CompatibleDigestItem` trait to appear in public interfaces.
+
 use primitives::Pair;
 use aura_primitives::AURA_ENGINE_ID;
-use runtime_primitives::generic::DigestItem;
-use parity_codec::{Encode, Decode};
+use runtime_primitives::generic::{DigestItem, OpaqueDigestItemId};
+use parity_codec::{Encode, Codec};
+use std::fmt::Debug;
 
 type Signature<P> = <P as Pair>::Signature;
 
 /// A digest item which is usable with aura consensus.
-pub trait CompatibleDigestItem<T: Pair>: Sized {
+pub trait CompatibleDigestItem<P: Pair>: Sized {
 	/// Construct a digest item which contains a signature on the hash.
-	fn aura_seal(signature: Signature<T>) -> Self;
+	fn aura_seal(signature: Signature<P>) -> Self;
 
 	/// If this item is an Aura seal, return the signature.
-	fn as_aura_seal(&self) -> Option<&Signature<T>>;
+	fn as_aura_seal(&self) -> Option<Signature<P>>;
 
 	/// Construct a digest item which contains the slot number
 	fn aura_pre_digest(slot_num: u64) -> Self;
@@ -40,18 +42,17 @@ pub trait CompatibleDigestItem<T: Pair>: Sized {
 	fn as_aura_pre_digest(&self) -> Option<u64>;
 }
 
-impl<P, Hash> CompatibleDigestItem<P> for DigestItem<Hash, P::Public, P::Signature>
-	where P: Pair, P::Signature: Clone + Encode + Decode,
+impl<P, Hash> CompatibleDigestItem<P> for DigestItem<Hash> where
+	P: Pair,
+	Signature<P>: Codec,
+	Hash: Debug + Send + Sync + Eq + Clone + Codec + 'static
 {
 	fn aura_seal(signature: Signature<P>) -> Self {
-		DigestItem::Seal(AURA_ENGINE_ID, signature)
+		DigestItem::Seal(AURA_ENGINE_ID, signature.encode())
 	}
 
-	fn as_aura_seal(&self) -> Option<&Signature<P>> {
-		match self {
-			DigestItem::Seal(AURA_ENGINE_ID, ref sig) => Some(sig),
-			_ => None,
-		}
+	fn as_aura_seal(&self) -> Option<Signature<P>> {
+		self.try_to(OpaqueDigestItemId::Seal(&AURA_ENGINE_ID))
 	}
 
 	fn aura_pre_digest(slot_num: u64) -> Self {
@@ -59,9 +60,6 @@ impl<P, Hash> CompatibleDigestItem<P> for DigestItem<Hash, P::Public, P::Signatu
 	}
 
 	fn as_aura_pre_digest(&self) -> Option<u64> {
-		match self {
-			DigestItem::PreRuntime(AURA_ENGINE_ID, ref buffer) => Decode::decode(&mut &buffer[..]),
-			_ => None,
-		}
+		self.try_to(OpaqueDigestItemId::PreRuntime(&AURA_ENGINE_ID))
 	}
 }