Add extrinsic to improve position in a bag of bags-list (#9829)

* pallet-bags-list: Add `put_in_front_of` extrinsic

This PR adds the extrinsic `put_in_front_of` which allows the user to specify a `lighter` and `heavier` account within the same bag. The extrinsic will move `heavier` directly in front of `lighter`.  The parameter names refer to the fact that `lighter` must have a lower `VoteWeight` then `heavier`. 

In the ideal use case, where a user wants to improve the position of their account within a bag, the user would iterate the bag, starting from the head, and find the first node who's `VoteWeight` is less than theirs. They would then supply the `id` of the node as the `lighter` argument and their own `id` as the `heavier` argument.

* Test & Benchmarks

* Respect line width

* Remove List::put_in_fron_of tests; Remove AlreadyHigher error

* The dispatch origin for this call must be ...

* Add some periods

* Add back test to list module: put_in_front_of_exits_early_if_bag_not_found

* add test tests::pallet::heavier_is_head_lighter_is_not_terminal

* Cater for edge case of heavier being head

* Add ExtBuilder::add_aux_data; try to make some tests use simpler data

* Update frame/bags-list/src/list/tests.rs

* make insert_at_unchecked infallible

* Make it permissioned - only callable by heavier

* Add test cases for insert_at_unchecked

* Move counter update to insert_at; fix comments

* Address some feedback

* Make voteweight constructed with parameter_types

* Always set vote weight for Ids in build

* Add skip_genesis_ids

* Do not pass weight fn to List put_in_front_of

* Remove remants of CounterForListNodes

* fmt

* cargo run --quiet --release --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_bags_list --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/bags-list/src/weights.rs --template=./.maintain/frame-weight-template.hbs

* Delete messed up weights file

* Some place holder stuff so we can run bench in CI

* Fix

* cargo run --quiet --release --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_bags_list --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/bags-list/src/weights.rs --template=./.maintain/frame-weight-template.hbs

* Update frame/bags-list/src/list/mod.rs

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

* fmt

* Log + debug assert when refetching an Id

Co-authored-by: Parity Bot <admin@parity.io>
Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

substrate/frame/bags-list/src/lib.rs

@@ -173,6 +173,17 @@ pub mod pallet {
 		Rebagged { who: T::AccountId, from: VoteWeight, to: VoteWeight },
 	}
 
+	#[pallet::error]
+	#[cfg_attr(test, derive(PartialEq))]
+	pub enum Error<T> {
+		/// Attempted to place node in front of a node in another bag.
+		NotInSameBag,
+		/// Id not found in list.
+		IdNotFound,
+		/// An Id does not have a greater vote weight than another Id.
+		NotHeavier,
+	}
+
 	#[pallet::call]
 	impl<T: Config> Pallet<T> {
 		/// Declare that some `dislocated` account has, through rewards or penalties, sufficiently
@@ -190,6 +201,20 @@ pub mod pallet {
 			let _ = Pallet::<T>::do_rebag(&dislocated, current_weight);
 			Ok(())
 		}
+
+		/// Move the caller's Id directly in front of `lighter`.
+		///
+		/// The dispatch origin for this call must be _Signed_ and can only be called by the Id of
+		/// the account going in front of `lighter`.
+		///
+		/// Only works if
+		/// - both nodes are within the same bag,
+		/// - and `origin` has a greater `VoteWeight` than `lighter`.
+		#[pallet::weight(T::WeightInfo::put_in_front_of())]
+		pub fn put_in_front_of(origin: OriginFor<T>, lighter: T::AccountId) -> DispatchResult {
+			let heavier = ensure_signed(origin)?;
+			List::<T>::put_in_front_of(&lighter, &heavier).map_err(Into::into)
+		}
 	}
 
 	#[pallet::hooks]