Offchain Phragmén BREAKING. (#4517)

* Initial skeleton for offchain phragmen

* Basic compact encoding decoding for results

* add compact files

* Bring back Self::ensure_storage_upgraded();

* Make staking use compact stuff.

* First seemingly working version of reduce, full of todos

* Everything phragmen related works again.

* Signing made easier, still issues.

* Signing from offchain compile fine 😎

* make compact work with staked asssignment

* Evaluation basics are in place.

* Move reduce into crate. Document stuff

* move reduce into no_std

* Add files

* Remove other std deps. Runtime compiles

* Seemingly it is al stable; cycle implemented but not integrated.

* Add fuzzing code.

* Cleanup reduce a bit more.

* a metric ton of tests for staking; wip 🔨

* Implement a lot more of the tests.

* wip getting the unsigned stuff to work

* A bit gleanup for unsigned debug

* Clean and finalize compact code.

* Document reduce.

* Still problems with signing

* We officaly duct taped the transaction submission stuff. 🤓

* Deadlock with keys again

* Runtime builds

* Unsigned test works 🙌

* Some cleanups

* Make all the tests compile and stuff

* Minor cleanup

* fix more merge stuff

* Most tests work again.

* a very nasty bug in reduce

* Fix all integrations

* Fix more todos

* Revamp everything and everything

* Remove bogus test

* Some review grumbles.

* Some fixes

* Fix doc test

* loop for submission

* Fix cli, keyring etc.

* some cleanup

* Fix staking tests again

* fix per-things; bring patches from benchmarking

* better score prediction

* Add fuzzer, more patches.

* Some fixes

* More docs

* Remove unused generics

* Remove max-nominator footgun

* Better fuzzer

* Disable it ❌

* Bump.

* Another round of self-review

* Refactor a lot

* More major fixes in perThing

* Add new fuzz file

* Update lock

* fix fuzzing code.

* Fix nominator retain test

* Add slashing check

* Update frame/staking/src/tests.rs

Co-Authored-By: Joshy Orndorff <JoshOrndorff@users.noreply.github.com>

* Some formatting nits

* Review comments.

* Fix cargo file

* Almost all tests work again

* Update frame/staking/src/tests.rs

Co-Authored-By: thiolliere <gui.thiolliere@gmail.com>

* Fix review comments

* More review stuff

* Some nits

* Fix new staking / session / babe relation

* Update primitives/phragmen/src/lib.rs

Co-Authored-By: thiolliere <gui.thiolliere@gmail.com>

* Update primitives/phragmen/src/lib.rs

Co-Authored-By: thiolliere <gui.thiolliere@gmail.com>

* Update primitives/phragmen/compact/src/lib.rs

Co-Authored-By: thiolliere <gui.thiolliere@gmail.com>

* Some doc updates to slashing

* Fix derive

* Remove imports

* Remove unimplemented tests

* nits

* Remove dbg

* Better fuzzing params

* Remove unused pref map

* Deferred Slashing/Offence for offchain Phragmen  (#5151)

* Some boilerplate

* Add test

* One more test

* Review comments

* Fix build

* review comments

* fix more

* fix build

* Some cleanups and self-reviews

* More minor self reviews

* Final nits

* Some merge fixes.

* opt comment

* Fix build

* Fix build again.

* Update frame/staking/fuzz/fuzz_targets/submit_solution.rs

Co-Authored-By: Gavin Wood <gavin@parity.io>

* Update frame/staking/src/slashing.rs

Co-Authored-By: Gavin Wood <gavin@parity.io>

* Update frame/staking/src/offchain_election.rs

Co-Authored-By: Gavin Wood <gavin@parity.io>

* Fix review comments

* fix test

* === 🔑 Revamp without staking key.

* final round of changes.

* Fix cargo-deny

* Update frame/staking/src/lib.rs

Co-Authored-By: Gavin Wood <gavin@parity.io>

Co-authored-by: Joshy Orndorff <JoshOrndorff@users.noreply.github.com>
Co-authored-by: thiolliere <gui.thiolliere@gmail.com>
Co-authored-by: Gavin Wood <gavin@parity.io>

substrate/frame/staking/src/slashing.rs

@@ -16,11 +16,11 @@
 
 //! A slashing implementation for NPoS systems.
 //!
-//! For the purposes of the economic model, it is easiest to think of each validator
-//! of a nominator which nominates only its own identity.
+//! For the purposes of the economic model, it is easiest to think of each validator as a nominator
+//! which nominates only its own identity.
 //!
-//! The act of nomination signals intent to unify economic identity with the validator - to take part in the
-//! rewards of a job well done, and to take part in the punishment of a job done badly.
+//! The act of nomination signals intent to unify economic identity with the validator - to take
+//! part in the rewards of a job well done, and to take part in the punishment of a job done badly.
 //!
 //! There are 3 main difficulties to account for with slashing in NPoS:
 //!   - A nominator can nominate multiple validators and be slashed via any of them.
@@ -52,7 +52,7 @@ use super::{
 	EraIndex, Trait, Module, Store, BalanceOf, Exposure, Perbill, SessionInterface,
 	NegativeImbalanceOf, UnappliedSlash,
 };
-use sp_runtime::{traits::{Zero, Saturating}, PerThing};
+use sp_runtime::{traits::{Zero, Saturating}, PerThing, RuntimeDebug};
 use frame_support::{
 	StorageMap, StorageDoubleMap,
 	traits::{Currency, OnUnbalanced, Imbalance},
@@ -65,7 +65,7 @@ use codec::{Encode, Decode};
 const REWARD_F1: Perbill = Perbill::from_percent(50);
 
 /// The index of a slashing span - unique to each stash.
-pub(crate) type SpanIndex = u32;
+pub type SpanIndex = u32;
 
 // A range of start..end eras for a slashing span.
 #[derive(Encode, Decode)]
@@ -83,7 +83,7 @@ impl SlashingSpan {
 }
 
 /// An encoding of all of a nominator's slashing spans.
-#[derive(Encode, Decode)]
+#[derive(Encode, Decode, RuntimeDebug)]
 pub struct SlashingSpans {
 	// the index of the current slashing span of the nominator. different for
 	// every stash, resets when the account hits free balance 0.
@@ -143,7 +143,7 @@ impl SlashingSpans {
 	}
 
 	/// Yields the era index where the most recent non-zero slash occurred.
-	pub(crate) fn last_nonzero_slash(&self) -> EraIndex {
+	pub fn last_nonzero_slash(&self) -> EraIndex {
 		self.last_nonzero_slash
 	}