Migrate election-phragmen, election contracts and authorship to decl_error (#4479)

* Migrate election-phragmen

* Migrate elections

* Migrate contracts module

* Update authorship module

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/frame/authorship/src/lib.rs

@@ -22,7 +22,7 @@
 
 use sp_std::{result, prelude::*};
 use sp_std::collections::btree_set::BTreeSet;
-use frame_support::{decl_module, decl_storage, dispatch, ensure};
+use frame_support::{decl_module, decl_storage, decl_error, dispatch, ensure};
 use frame_support::traits::{FindAuthor, VerifySeal, Get};
 use codec::{Encode, Decode};
 use frame_system::ensure_none;
@@ -161,8 +161,30 @@ decl_storage! {
 	}
 }
 
+decl_error! {
+	/// Error for the authorship module.
+	pub enum Error for Module<T: Trait> {
+		/// The uncle parent not in the chain.
+		InvalidUncleParent,
+		/// Uncles already set in the block.
+		UnclesAlreadySet,
+		/// Too many uncles.
+		TooManyUncles,
+		/// The uncle is genesis.
+		GenesisUncle,
+		/// The uncle is too high in chain.
+		TooHighUncle,
+		/// The uncle is already included.
+		UncleAlreadyIncluded,
+		/// The uncle isn't recent enough to be included.
+		OldUncle,
+	}
+}
+
 decl_module! {
 	pub struct Module<T: Trait> for enum Call where origin: T::Origin {
+		type Error = Error<T>;
+
 		fn on_initialize(now: T::BlockNumber) {
 			let uncle_generations = T::UncleGenerations::get();
 			// prune uncles that are older than the allowed number of generations.
@@ -186,10 +208,10 @@ decl_module! {
 		#[weight = SimpleDispatchInfo::FixedOperational(10_000)]
 		fn set_uncles(origin, new_uncles: Vec<T::Header>) -> dispatch::DispatchResult {
 			ensure_none(origin)?;
-			ensure!(new_uncles.len() <= MAX_UNCLES, "Too many uncles");
+			ensure!(new_uncles.len() <= MAX_UNCLES, Error::<T>::TooManyUncles);
 
 			if <Self as Store>::DidSetUncles::get() {
-				Err("Uncles already set in block.")?
+				Err(Error::<T>::UnclesAlreadySet)?
 			}
 			<Self as Store>::DidSetUncles::put(true);
 
@@ -251,7 +273,7 @@ impl<T: Trait> Module<T> {
 		uncle: &T::Header,
 		existing_uncles: I,
 		accumulator: &mut <T::FilterUncle as FilterUncle<T::Header, T::AccountId>>::Accumulator,
-	) -> Result<Option<T::AccountId>, &'static str>
+	) -> Result<Option<T::AccountId>, dispatch::DispatchError>
 	{
 		let now = <frame_system::Module<T>>::block_number();
 
@@ -269,34 +291,34 @@ impl<T: Trait> Module<T> {
 		let hash = uncle.hash();
 
 		if uncle.number() < &One::one() {
-			return Err("uncle is genesis");
+			return Err(Error::<T>::GenesisUncle.into());
 		}
 
 		if uncle.number() > &maximum_height {
-			return Err("uncle is too high in chain");
+			return Err(Error::<T>::TooHighUncle.into());
 		}
 
 		{
 			let parent_number = uncle.number().clone() - One::one();
 			let parent_hash = <frame_system::Module<T>>::block_hash(&parent_number);
 			if &parent_hash != uncle.parent_hash() {
-				return Err("uncle parent not in chain");
+				return Err(Error::<T>::InvalidUncleParent.into());
 			}
 		}
 
 		if uncle.number() < &minimum_height {
-			return Err("uncle not recent enough to be included");
+			return Err(Error::<T>::OldUncle.into());
 		}
 
 		let duplicate = existing_uncles.into_iter().find(|h| **h == hash).is_some();
 		let in_chain = <frame_system::Module<T>>::block_hash(uncle.number()) == hash;
 
 		if duplicate || in_chain {
-			return Err("uncle already included")
+			return Err(Error::<T>::UncleAlreadyIncluded.into())
 		}
 
 		// check uncle validity.
-		T::FilterUncle::filter_uncle(&uncle, accumulator)
+		T::FilterUncle::filter_uncle(&uncle, accumulator).map_err(|e| Into::into(e))
 	}
 
 	fn prune_old_uncles(minimum_height: T::BlockNumber) {
@@ -360,7 +382,7 @@ impl<T: Trait> ProvideInherent for Module<T> {
 	fn check_inherent(call: &Self::Call, _data: &InherentData) -> result::Result<(), Self::Error> {
 		match call {
 			Call::set_uncles(ref uncles) if uncles.len() > MAX_UNCLES => {
-				Err(InherentError::Uncles("Too many uncles".into()))
+				Err(InherentError::Uncles(Error::<T>::TooManyUncles.as_str().into()))
 			},
 			_ => {
 				Ok(())
@@ -566,7 +588,7 @@ mod tests {
 				);
 				assert_eq!(
 					Authorship::verify_and_import_uncles(vec![uncle_a.clone(), uncle_a.clone()]),
-					Err("uncle already included".into()),
+					Err(Error::<Test>::UncleAlreadyIncluded.into()),
 				);
 			}
 
@@ -581,7 +603,7 @@ mod tests {
 
 				assert_eq!(
 					Authorship::verify_and_import_uncles(vec![uncle_a.clone()]),
-					Err("uncle already included".into()),
+					Err(Error::<Test>::UncleAlreadyIncluded.into()),
 				);
 			}
 
@@ -591,7 +613,7 @@ mod tests {
 
 				assert_eq!(
 					Authorship::verify_and_import_uncles(vec![uncle_clone]),
-					Err("uncle already included".into()),
+					Err(Error::<Test>::UncleAlreadyIncluded.into()),
 				);
 			}
 
@@ -615,7 +637,7 @@ mod tests {
 
 				assert_eq!(
 					Authorship::verify_and_import_uncles(vec![gen_2]),
-					Err("uncle not recent enough to be included".into()),
+					Err(Error::<Test>::OldUncle.into()),
 				);
 			}
 

substrate/frame/contracts/src/lib.rs

@@ -121,7 +121,7 @@ use sp_runtime::{
 };
 use frame_support::dispatch::{DispatchResult, Dispatchable};
 use frame_support::{
-	Parameter, decl_module, decl_event, decl_storage, storage::child,
+	Parameter, decl_module, decl_event, decl_storage, decl_error, storage::child,
 	parameter_types, IsSubType,
 	weights::DispatchInfo,
 };
@@ -467,9 +467,29 @@ impl<T: Trait> ComputeDispatchFee<<T as Trait>::Call, BalanceOf<T>> for DefaultD
 	}
 }
 
+decl_error! {
+	/// Error for the contracts module.
+	pub enum Error for Module<T: Trait> {
+		/// A new schedule must have a greater version than the current one.
+		InvalidScheduleVersion,
+		/// An origin must be signed or inherent and auxiliary sender only provided on inherent.
+		InvalidSurchargeClaim,
+		/// Cannot restore from nonexisting or tombstone contract.
+		InvalidSourceContract,
+		/// Cannot restore to nonexisting or alive contract.
+		InvalidDestinationContract,
+		/// Tombstones don't match.
+		InvalidTombstone,
+		/// An origin TrieId written in the current block.
+		InvalidContractOrigin
+	}
+}
+
 decl_module! {
 	/// Contracts module.
 	pub struct Module<T: Trait> for enum Call where origin: <T as frame_system::Trait>::Origin {
+		type Error = Error<T>;
+
 		/// Number of block delay an extrinsic claim surcharge has.
 		///
 		/// When claim surcharge is called by an extrinsic the rent is checked
@@ -542,7 +562,7 @@ decl_module! {
 		pub fn update_schedule(origin, schedule: Schedule) -> DispatchResult {
 			ensure_root(origin)?;
 			if <Module<T>>::current_schedule().version >= schedule.version {
-				Err("new schedule must have a greater version than current")?
+				Err(Error::<T>::InvalidScheduleVersion)?
 			}
 
 			Self::deposit_event(RawEvent::ScheduleUpdated(schedule.version));
@@ -636,10 +656,7 @@ decl_module! {
 				(Ok(frame_system::RawOrigin::None), Some(aux_sender)) => {
 					(false, aux_sender)
 				},
-				_ => Err(
-					"Invalid surcharge claim: origin must be signed or \
-					inherent and auxiliary sender only provided on inherent"
-				)?,
+				_ => Err(Error::<T>::InvalidSurchargeClaim)?,
 			};
 
 			// Add some advantage for block producers (who send unsigned extrinsics) by
@@ -786,17 +803,17 @@ impl<T: Trait> Module<T> {
 	) -> DispatchResult {
 		let mut origin_contract = <ContractInfoOf<T>>::get(&origin)
 			.and_then(|c| c.get_alive())
-			.ok_or("Cannot restore from inexisting or tombstone contract")?;
+			.ok_or(Error::<T>::InvalidSourceContract)?;
 
 		let current_block = <frame_system::Module<T>>::block_number();
 
 		if origin_contract.last_write == Some(current_block) {
-			Err("Origin TrieId written in the current block")?
+			Err(Error::<T>::InvalidContractOrigin)?
 		}
 
 		let dest_tombstone = <ContractInfoOf<T>>::get(&dest)
 			.and_then(|c| c.get_tombstone())
-			.ok_or("Cannot restore to inexisting or alive contract")?;
+			.ok_or(Error::<T>::InvalidDestinationContract)?;
 
 		let last_write = if !delta.is_empty() {
 			Some(current_block)
@@ -841,7 +858,7 @@ impl<T: Trait> Module<T> {
 				);
 			}
 
-			return Err("Tombstones don't match".into());
+			return Err(Error::<T>::InvalidTombstone.into());
 		}
 
 		origin_contract.storage_size -= key_values_taken.iter()

substrate/frame/elections-phragmen/src/lib.rs

@@ -83,9 +83,9 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 
 use sp_std::prelude::*;
-use sp_runtime::{print, DispatchResult, traits::{Zero, StaticLookup, Bounded, Convert}};
+use sp_runtime::{print, DispatchResult, DispatchError, traits::{Zero, StaticLookup, Bounded, Convert}};
 use frame_support::{
-	decl_storage, decl_event, ensure, decl_module, weights::SimpleDispatchInfo,
+	decl_storage, decl_event, ensure, decl_module, decl_error, weights::SimpleDispatchInfo,
 	traits::{
 		Currency, Get, LockableCurrency, LockIdentifier, ReservableCurrency, WithdrawReasons,
 		ChangeMembers, OnUnbalanced, WithdrawReason
@@ -167,8 +167,44 @@ decl_storage! {
 	}
 }
 
+decl_error! {
+	/// Error for the elections-phragmen module.
+	pub enum Error for Module<T: Trait> {
+		/// Cannot vote when no candidates or members exist.
+		UnableToVote,
+		/// Must vote for at least one candidate.
+		NoVotes,
+		/// Cannot vote more than candidates.
+		TooManyVotes,
+		/// Cannot vote more than maximum allowed.
+		MaximumVotesExceeded,
+		/// Cannot vote with stake less than minimum balance.
+		LowBalance,
+		/// Voter can not pay voting bond.
+		UnableToPayBond,
+		/// Must be a voter.
+		MustBeVoter,
+		/// Cannot report self.
+		ReportSelf,
+		/// Duplicated candidate submission.
+		DuplicatedCandidate,
+		/// Member cannot re-submit candidacy.
+		MemberSubmit,
+		/// Runner cannot re-submit candidacy.
+		RunnerSubmit,
+		/// Candidate does not have enough funds.
+		InsufficientCandidateFunds,
+		/// Origin is not a candidate, member or a runner up.
+		InvalidOrigin,
+		/// Not a member.
+		NotMember,
+	}
+}
+
 decl_module! {
 	pub struct Module<T: Trait> for enum Call where origin: T::Origin {
+		type Error = Error<T>;
+
 		fn deposit_event() = default;
 
 		const CandidacyBond: BalanceOf<T> = T::CandidacyBond::get();
@@ -201,20 +237,20 @@ decl_module! {
 			// addition is valid: candidates and members never overlap.
 			let allowed_votes = candidates_count + members_count;
 
-			ensure!(!allowed_votes.is_zero(), "cannot vote when no candidates or members exist");
-			ensure!(votes.len() <= allowed_votes, "cannot vote more than candidates");
-			ensure!(votes.len() <= MAXIMUM_VOTE, "cannot vote more than maximum allowed");
-			ensure!(!votes.is_empty(), "must vote for at least one candidate.");
+			ensure!(!allowed_votes.is_zero(), Error::<T>::UnableToVote);
+			ensure!(votes.len() <= allowed_votes, Error::<T>::TooManyVotes);
+			ensure!(votes.len() <= MAXIMUM_VOTE, Error::<T>::MaximumVotesExceeded);
+			ensure!(!votes.is_empty(), Error::<T>::NoVotes);
 
 			ensure!(
 				value > T::Currency::minimum_balance(),
-				"cannot vote with stake less than minimum balance"
+				Error::<T>::LowBalance,
 			);
 
 			if !Self::is_voter(&who) {
 				// first time voter. Reserve bond.
 				T::Currency::reserve(&who, T::VotingBond::get())
-					.map_err(|_| "voter can not pay voting bond")?;
+					.map_err(|_| Error::<T>::UnableToPayBond)?;
 			}
 			// Amount to be locked up.
 			let locked_balance = value.min(T::Currency::total_balance(&who));
@@ -242,7 +278,7 @@ decl_module! {
 		fn remove_voter(origin) {
 			let who = ensure_signed(origin)?;
 
-			ensure!(Self::is_voter(&who), "must be a voter");
+			ensure!(Self::is_voter(&who), Error::<T>::MustBeVoter);
 
 			Self::do_remove_voter(&who, true);
 		}
@@ -265,8 +301,8 @@ decl_module! {
 			let reporter = ensure_signed(origin)?;
 			let target = T::Lookup::lookup(target)?;
 
-			ensure!(reporter != target, "cannot report self");
-			ensure!(Self::is_voter(&reporter), "reporter must be a voter");
+			ensure!(reporter != target, Error::<T>::ReportSelf);
+			ensure!(Self::is_voter(&reporter), Error::<T>::MustBeVoter);
 
 			// Checking if someone is a candidate and a member here is O(LogN), making the whole
 			// function O(MLonN) with N candidates in total and M of them being voted by `target`.
@@ -308,15 +344,15 @@ decl_module! {
 			let who = ensure_signed(origin)?;
 
 			let is_candidate = Self::is_candidate(&who);
-			ensure!(is_candidate.is_err(), "duplicate candidate submission");
+			ensure!(is_candidate.is_err(), Error::<T>::DuplicatedCandidate);
 			// assured to be an error, error always contains the index.
 			let index = is_candidate.unwrap_err();
 
-			ensure!(!Self::is_member(&who), "member cannot re-submit candidacy");
-			ensure!(!Self::is_runner(&who), "runner cannot re-submit candidacy");
+			ensure!(!Self::is_member(&who), Error::<T>::MemberSubmit);
+			ensure!(!Self::is_runner(&who), Error::<T>::RunnerSubmit);
 
 			T::Currency::reserve(&who, T::CandidacyBond::get())
-				.map_err(|_| "candidate does not have enough funds")?;
+				.map_err(|_| Error::<T>::InsufficientCandidateFunds)?;
 
 			<Candidates<T>>::mutate(|c| c.insert(index, who));
 		}
@@ -373,7 +409,7 @@ decl_module! {
 				return Ok(());
 			}
 
-			Err("origin is not a candidate, member or a runner up.")?
+			Err(Error::<T>::InvalidOrigin)?
 		}
 
 		/// Remove a particular member from the set. This is effective immediately and the bond of
@@ -402,7 +438,7 @@ decl_module! {
 				if !had_replacement {
 					Self::do_phragmen();
 				}
-			}).map_err(Into::into)
+			})
 		}
 
 		/// What to do at the end of each block. Checks if an election needs to happen or not.
@@ -444,7 +480,7 @@ impl<T: Trait> Module<T> {
 	/// accordingly. Furthermore, the membership change is reported.
 	///
 	/// O(phragmen) in the worse case.
-	fn remove_and_replace_member(who: &T::AccountId) -> Result<bool, &'static str> {
+	fn remove_and_replace_member(who: &T::AccountId) -> Result<bool, DispatchError> {
 		let mut members_with_stake = Self::members();
 		if let Ok(index) = members_with_stake.binary_search_by(|(ref m, ref _s)| m.cmp(who)) {
 			members_with_stake.remove(index);
@@ -469,7 +505,7 @@ impl<T: Trait> Module<T> {
 			}
 			result
 		} else {
-			Err("not a member")
+			Err(Error::<T>::NotMember)?
 		}
 	}
 
@@ -1072,7 +1108,7 @@ mod tests {
 			assert_eq!(Elections::candidates(), vec![1]);
 			assert_noop!(
 				Elections::submit_candidacy(Origin::signed(1)),
-				"duplicate candidate submission"
+				Error::<Test>::DuplicatedCandidate,
 			);
 		});
 	}
@@ -1093,7 +1129,7 @@ mod tests {
 
 			assert_noop!(
 				Elections::submit_candidacy(Origin::signed(5)),
-				"member cannot re-submit candidacy"
+				Error::<Test>::MemberSubmit,
 			);
 		});
 	}
@@ -1116,7 +1152,7 @@ mod tests {
 
 			assert_noop!(
 				Elections::submit_candidacy(Origin::signed(3)),
-				"runner cannot re-submit candidacy",
+				Error::<Test>::RunnerSubmit,
 			);
 		});
 	}
@@ -1127,7 +1163,7 @@ mod tests {
 			assert_eq!(Elections::candidates(), Vec::<u64>::new());
 			assert_noop!(
 				Elections::submit_candidacy(Origin::signed(7)),
-				"candidate does not have enough funds",
+				Error::<Test>::InsufficientCandidateFunds,
 			);
 		});
 	}
@@ -1186,7 +1222,7 @@ mod tests {
 		ExtBuilder::default().build().execute_with(|| {
 			assert_noop!(
 				Elections::vote(Origin::signed(2), vec![], 20),
-				"cannot vote when no candidates or members exist"
+				Error::<Test>::UnableToVote,
 			);
 		});
 	}
@@ -1217,7 +1253,7 @@ mod tests {
 
 			assert_noop!(
 				Elections::vote(Origin::signed(2), vec![10, 20, 30], 20),
-				"cannot vote more than candidates",
+				Error::<Test>::TooManyVotes,
 			);
 		});
 	}
@@ -1230,7 +1266,7 @@ mod tests {
 
 			assert_noop!(
 				Elections::vote(Origin::signed(2), vec![4], 1),
-				"cannot vote with stake less than minimum balance",
+				Error::<Test>::LowBalance,
 			);
 		})
 	}
@@ -1276,7 +1312,7 @@ mod tests {
 	#[test]
 	fn non_voter_remove_should_not_work() {
 		ExtBuilder::default().build().execute_with(|| {
-			assert_noop!(Elections::remove_voter(Origin::signed(3)), "must be a voter");
+			assert_noop!(Elections::remove_voter(Origin::signed(3)), Error::<Test>::MustBeVoter);
 		});
 	}
 
@@ -1289,7 +1325,7 @@ mod tests {
 			assert_ok!(Elections::remove_voter(Origin::signed(2)));
 			assert_eq!(all_voters(), vec![]);
 
-			assert_noop!(Elections::remove_voter(Origin::signed(2)), "must be a voter");
+			assert_noop!(Elections::remove_voter(Origin::signed(2)), Error::<Test>::MustBeVoter);
 		});
 	}
 
@@ -1318,7 +1354,7 @@ mod tests {
 		ExtBuilder::default().build().execute_with(|| {
 			assert_noop!(
 				Elections::report_defunct_voter(Origin::signed(1), 2),
-				"reporter must be a voter",
+				Error::<Test>::MustBeVoter,
 			);
 		});
 	}
@@ -2032,7 +2068,7 @@ mod tests {
 		ExtBuilder::default().build().execute_with(|| {
 			assert_noop!(
 				Elections::renounce_candidacy(Origin::signed(5)),
-				"origin is not a candidate, member or a runner up.",
+				Error::<Test>::InvalidOrigin,
 			);
 		})
 	}

substrate/frame/elections/src/lib.rs

@@ -29,7 +29,7 @@ use sp_runtime::{
 	traits::{Zero, One, StaticLookup, Bounded, Saturating},
 };
 use frame_support::{
-	decl_storage, decl_event, ensure, decl_module,
+	decl_storage, decl_event, ensure, decl_module, decl_error,
 	weights::SimpleDispatchInfo,
 	traits::{
 		Currency, ExistenceRequirement, Get, LockableCurrency, LockIdentifier,
@@ -267,8 +267,72 @@ decl_storage! {
 	}
 }
 
+decl_error! {
+	/// Error for the elections module.
+	pub enum Error for Module<T: Trait> {
+		/// Reporter must be a voter.
+		NotVoter,
+		/// Target for inactivity cleanup must be active.
+		InactiveTarget,
+		/// Cannot reap during presentation period.
+		CannotReapPresenting,
+		/// Cannot reap during grace period.
+		ReapGrace,
+		/// Not a proxy.
+		NotProxy,
+		/// Invalid reporter index.
+		InvalidReporterIndex,
+		/// Invalid target index.
+		InvalidTargetIndex,
+		/// Invalid vote index.
+		InvalidVoteIndex,
+		/// Cannot retract when presenting.
+		CannotRetractPresenting,
+		/// Cannot retract non-voter.
+		RetractNonVoter,
+		/// Invalid retraction index.
+		InvalidRetractionIndex,
+		/// Duplicate candidate submission.
+		DuplicatedCandidate,
+		/// Invalid candidate slot.
+		InvalidCandidateSlot,
+		/// Candidate has not enough funds.
+		InsufficientCandidateFunds,
+		/// Presenter must have sufficient slashable funds.
+		InsufficientPresenterFunds,
+		/// Stake deposited to present winner and be added to leaderboard should be non-zero.
+		ZeroDeposit,
+		/// Candidate not worthy of leaderboard.
+		UnworthyCandidate,
+		/// Leaderboard must exist while present phase active.
+		LeaderboardMustExist,
+		/// Cannot present outside of presentation period.
+		NotPresentationPeriod,
+		/// Presented candidate must be current.
+		InvalidCandidate,
+		/// Duplicated presentation.
+		DuplicatedPresentation,
+		/// Incorrect total.
+		IncorrectTotal,
+		/// Invalid voter index.
+		InvalidVoterIndex,
+		/// New voter must have sufficient funds to pay the bond.
+		InsufficientVoterFunds,
+		/// Locked value must be more than limit.
+		InsufficientLockedValue,
+		/// Amount of candidate votes cannot exceed amount of candidates.
+		TooManyVotes,
+		/// Amount of candidates to receive approval votes should be non-zero.
+		ZeroCandidates,
+		/// No approval changes during presentation period.
+		ApprovalPresentation,
+	}
+}
+
 decl_module! {
 	pub struct Module<T: Trait> for enum Call where origin: T::Origin {
+		type Error = Error<T>;
+
 		/// How much should be locked up in order to submit one's candidacy. A reasonable
 		/// default value is 9.
 		const CandidacyBond: BalanceOf<T> = T::CandidacyBond::get();
@@ -363,7 +427,7 @@ decl_module! {
 			hint: SetIndex,
 			#[compact] value: BalanceOf<T>
 		) -> DispatchResult {
-			let who = Self::proxy(ensure_signed(origin)?).ok_or("not a proxy")?;
+			let who = Self::proxy(ensure_signed(origin)?).ok_or(Error::<T>::NotProxy)?;
 			Self::do_set_approvals(who, votes, index, hint, value)
 		}
 
@@ -390,26 +454,25 @@ decl_module! {
 			let reporter = ensure_signed(origin)?;
 			let who = T::Lookup::lookup(who)?;
 
-			ensure!(!Self::presentation_active(), "cannot reap during presentation period");
-			ensure!(Self::voter_info(&reporter).is_some(), "reporter must be a voter");
+			ensure!(!Self::presentation_active(), Error::<T>::CannotReapPresenting);
+			ensure!(Self::voter_info(&reporter).is_some(), Error::<T>::NotVoter);
 
-			let info = Self::voter_info(&who)
-				.ok_or("target for inactivity cleanup must be active")?;
+			let info = Self::voter_info(&who).ok_or(Error::<T>::InactiveTarget)?;
 			let last_active = info.last_active;
 
-			ensure!(assumed_vote_index == Self::vote_index(), "vote index not current");
+			ensure!(assumed_vote_index == Self::vote_index(), Error::<T>::InvalidVoteIndex);
 			ensure!(
 				assumed_vote_index > last_active + T::InactiveGracePeriod::get(),
-				"cannot reap during grace period"
+				Error::<T>::ReapGrace,
 			);
 
 			let reporter_index = reporter_index as usize;
 			let who_index = who_index as usize;
-			let assumed_reporter = Self::voter_at(reporter_index).ok_or("invalid reporter index")?;
-			let assumed_who = Self::voter_at(who_index).ok_or("invalid target index")?;
+			let assumed_reporter = Self::voter_at(reporter_index).ok_or(Error::<T>::InvalidReporterIndex)?;
+			let assumed_who = Self::voter_at(who_index).ok_or(Error::<T>::InvalidTargetIndex)?;
 
-			ensure!(assumed_reporter == reporter, "bad reporter index");
-			ensure!(assumed_who == who, "bad target index");
+			ensure!(assumed_reporter == reporter, Error::<T>::InvalidReporterIndex);
+			ensure!(assumed_who == who, Error::<T>::InvalidTargetIndex);
 
 			// will definitely kill one of reporter or who now.
 
@@ -458,11 +521,11 @@ decl_module! {
 		fn retract_voter(origin, #[compact] index: u32) {
 			let who = ensure_signed(origin)?;
 
-			ensure!(!Self::presentation_active(), "cannot retract when presenting");
-			ensure!(<VoterInfoOf<T>>::exists(&who), "cannot retract non-voter");
+			ensure!(!Self::presentation_active(), Error::<T>::CannotRetractPresenting);
+			ensure!(<VoterInfoOf<T>>::exists(&who), Error::<T>::RetractNonVoter);
 			let index = index as usize;
-			let voter = Self::voter_at(index).ok_or("retraction index invalid")?;
-			ensure!(voter == who, "retraction index mismatch");
+			let voter = Self::voter_at(index).ok_or(Error::<T>::InvalidRetractionIndex)?;
+			ensure!(voter == who, Error::<T>::InvalidRetractionIndex);
 
 			Self::remove_voter(&who, index);
 			T::Currency::unreserve(&who, T::VotingBond::get());
@@ -486,18 +549,18 @@ decl_module! {
 		fn submit_candidacy(origin, #[compact] slot: u32) {
 			let who = ensure_signed(origin)?;
 
-			ensure!(!Self::is_a_candidate(&who), "duplicate candidate submission");
+			ensure!(!Self::is_a_candidate(&who), Error::<T>::DuplicatedCandidate);
 			let slot = slot as usize;
 			let count = Self::candidate_count() as usize;
 			let candidates = Self::candidates();
 			ensure!(
 				(slot == count && count == candidates.len()) ||
 					(slot < candidates.len() && candidates[slot] == T::AccountId::default()),
-				"invalid candidate slot"
+				Error::<T>::InvalidCandidateSlot,
 			);
 			// NOTE: This must be last as it has side-effects.
 			T::Currency::reserve(&who, T::CandidacyBond::get())
-				.map_err(|_| "candidate has not enough funds")?;
+				.map_err(|_| Error::<T>::InsufficientCandidateFunds)?;
 
 			<RegisterInfoOf<T>>::insert(&who, (Self::vote_index(), slot as u32));
 			let mut candidates = candidates;
@@ -529,35 +592,35 @@ decl_module! {
 			let who = ensure_signed(origin)?;
 			ensure!(
 				!total.is_zero(),
-				"stake deposited to present winner and be added to leaderboard should be non-zero",
+				Error::<T>::ZeroDeposit,
 			);
 
 			let candidate = T::Lookup::lookup(candidate)?;
-			ensure!(index == Self::vote_index(), "index not current");
+			ensure!(index == Self::vote_index(), Error::<T>::InvalidVoteIndex);
 			let (_, _, expiring) = Self::next_finalize()
-				.ok_or("cannot present outside of presentation period")?;
+				.ok_or(Error::<T>::NotPresentationPeriod)?;
 			let bad_presentation_punishment =
 				T::PresentSlashPerVoter::get()
 				* BalanceOf::<T>::from(Self::voter_count() as u32);
 			ensure!(
 				T::Currency::can_slash(&who, bad_presentation_punishment),
-				"presenter must have sufficient slashable funds"
+				Error::<T>::InsufficientPresenterFunds,
 			);
 
 			let mut leaderboard = Self::leaderboard()
-				.ok_or("leaderboard must exist while present phase active")?;
-			ensure!(total > leaderboard[0].0, "candidate not worthy of leaderboard");
+				.ok_or(Error::<T>::LeaderboardMustExist)?;
+			ensure!(total > leaderboard[0].0, Error::<T>::UnworthyCandidate);
 
 			if let Some(p) = Self::members().iter().position(|&(ref c, _)| c == &candidate) {
 				ensure!(
 					p < expiring.len(),
-					"candidate must not form a duplicated member if elected"
+					Error::<T>::DuplicatedCandidate,
 				);
 			}
 
 			let voters = Self::all_voters();
 			let (registered_since, candidate_index): (VoteIndex, u32) =
-				Self::candidate_reg_info(&candidate).ok_or("presented candidate must be current")?;
+				Self::candidate_reg_info(&candidate).ok_or(Error::<T>::InvalidCandidate)?;
 			let actual_total = voters.iter()
 				.filter_map(|maybe_voter| maybe_voter.as_ref())
 				.filter_map(|voter| match Self::voter_info(voter) {
@@ -586,7 +649,7 @@ decl_module! {
 				// better safe than sorry.
 				let imbalance = T::Currency::slash(&who, bad_presentation_punishment).0;
 				T::BadPresentation::on_unbalanced(imbalance);
-				Err(if dupe { "duplicate presentation" } else { "incorrect total" })?
+				Err(if dupe { Error::<T>::DuplicatedPresentation } else { Error::<T>::IncorrectTotal })?
 			}
 		}
 
@@ -752,11 +815,11 @@ impl<T: Trait> Module<T> {
 	) -> DispatchResult {
 		let candidates_len = <Self as Store>::Candidates::decode_len().unwrap_or(0_usize);
 
-		ensure!(!Self::presentation_active(), "no approval changes during presentation period");
-		ensure!(index == Self::vote_index(), "incorrect vote index");
+		ensure!(!Self::presentation_active(), Error::<T>::ApprovalPresentation);
+		ensure!(index == Self::vote_index(), Error::<T>::InvalidVoteIndex);
 		ensure!(
 			!candidates_len.is_zero(),
-			"amount of candidates to receive approval votes should be non-zero"
+			Error::<T>::ZeroCandidates,
 		);
 		// Prevent a vote from voters that provide a list of votes that exceeds the candidates
 		// length since otherwise an attacker may be able to submit a very long list of `votes` that
@@ -764,9 +827,9 @@ impl<T: Trait> Module<T> {
 		// bond would cover.
 		ensure!(
 			candidates_len >= votes.len(),
-			"amount of candidate votes cannot exceed amount of candidates"
+			Error::<T>::TooManyVotes,
 		);
-		ensure!(value >= T::MinimumVotingLock::get(), "locked value must be more than limit");
+		ensure!(value >= T::MinimumVotingLock::get(), Error::<T>::InsufficientLockedValue);
 
 		// Amount to be locked up.
 		let mut locked_balance = value.min(T::Currency::total_balance(&who));
@@ -775,8 +838,8 @@ impl<T: Trait> Module<T> {
 
 		if let Some(info) = Self::voter_info(&who) {
 			// already a voter. Index must be valid. No fee. update pot. O(1)
-			let voter = Self::voter_at(hint).ok_or("invalid voter index")?;
-			ensure!(voter == who, "wrong voter index");
+			let voter = Self::voter_at(hint).ok_or(Error::<T>::InvalidVoterIndex)?;
+			ensure!(voter == who, Error::<T>::InvalidVoterIndex);
 
 			// write new accumulated offset.
 			let last_win = info.last_win;
@@ -787,7 +850,7 @@ impl<T: Trait> Module<T> {
 			// not yet a voter. Index _could be valid_. Fee might apply. Bond will be reserved O(1).
 			ensure!(
 				T::Currency::free_balance(&who) > T::VotingBond::get(),
-				"new voter must have sufficient funds to pay the bond"
+				Error::<T>::InsufficientVoterFunds,
 			);
 
 			let (set_index, vec_index) = Self::split_index(hint, VOTER_SET_SIZE);

substrate/frame/elections/src/tests.rs

@@ -256,7 +256,7 @@ fn chunking_voter_index_does_not_take_holes_into_account() {
 		// proof: can submit a new approval with the old index.
 		assert_noop!(
 			Elections::set_approvals(Origin::signed(65), vec![], 0, 64 - 2, 10),
-			"wrong voter index"
+			Error::<Test>::InvalidVoterIndex,
 		);
 		assert_ok!(Elections::set_approvals(Origin::signed(65), vec![], 0, 64, 10));
 	})
@@ -338,12 +338,12 @@ fn voting_subsequent_set_approvals_checks_voter_index() {
 		// invalid index
 		assert_noop!(
 			Elections::set_approvals(Origin::signed(4), vec![true], 0, 5, 40),
-			"invalid voter index"
+			Error::<Test>::InvalidVoterIndex,
 		);
 		// wrong index
 		assert_noop!(
 			Elections::set_approvals(Origin::signed(4), vec![true], 0, 0, 40),
-			"wrong voter index"
+			Error::<Test>::InvalidVoterIndex,
 		);
 		// correct
 		assert_ok!(Elections::set_approvals(Origin::signed(4), vec![true], 0, 1, 40));
@@ -357,7 +357,7 @@ fn voting_cannot_lock_less_than_limit() {
 
 		assert_noop!(
 			Elections::set_approvals(Origin::signed(3), vec![], 0, 0, 4),
-			"locked value must be more than limit",
+			Error::<Test>::InsufficientLockedValue,
 		);
 		assert_ok!(Elections::set_approvals(Origin::signed(3), vec![], 0, 0, 5));
 	});
@@ -414,7 +414,7 @@ fn voting_without_any_candidate_count_should_not_work() {
 
 		assert_noop!(
 			Elections::set_approvals(Origin::signed(4), vec![], 0, 0, 40),
-			"amount of candidates to receive approval votes should be non-zero"
+			Error::<Test>::ZeroCandidates,
 		);
 	});
 }
@@ -429,7 +429,7 @@ fn voting_setting_an_approval_vote_count_more_than_candidate_count_should_not_wo
 
 		assert_noop!(
 			Elections::set_approvals(Origin::signed(4),vec![true, true], 0, 0, 40),
-			"amount of candidate votes cannot exceed amount of candidates"
+			Error::<Test>::TooManyVotes,
 		);
 	});
 }
@@ -507,7 +507,7 @@ fn voting_invalid_retraction_index_should_not_work() {
 		assert_ok!(Elections::set_approvals(Origin::signed(1), vec![true], 0, 0, 10));
 		assert_ok!(Elections::set_approvals(Origin::signed(2), vec![true], 0, 0, 20));
 		assert_eq!(voter_ids(), vec![1, 2]);
-		assert_noop!(Elections::retract_voter(Origin::signed(1), 1), "retraction index mismatch");
+		assert_noop!(Elections::retract_voter(Origin::signed(1), 1), Error::<Test>::InvalidRetractionIndex);
 	});
 }
 
@@ -518,7 +518,7 @@ fn voting_overflow_retraction_index_should_not_work() {
 		assert_ok!(Elections::submit_candidacy(Origin::signed(3), 0));
 
 		assert_ok!(Elections::set_approvals(Origin::signed(1), vec![true], 0, 0, 10));
-		assert_noop!(Elections::retract_voter(Origin::signed(1), 1), "retraction index invalid");
+		assert_noop!(Elections::retract_voter(Origin::signed(1), 1), Error::<Test>::InvalidRetractionIndex);
 	});
 }
 
@@ -529,7 +529,7 @@ fn voting_non_voter_retraction_should_not_work() {
 		assert_ok!(Elections::submit_candidacy(Origin::signed(3), 0));
 
 		assert_ok!(Elections::set_approvals(Origin::signed(1), vec![true], 0, 0, 10));
-		assert_noop!(Elections::retract_voter(Origin::signed(2), 0), "cannot retract non-voter");
+		assert_noop!(Elections::retract_voter(Origin::signed(2), 0), Error::<Test>::RetractNonVoter);
 	});
 }
 
@@ -627,7 +627,7 @@ fn retracting_inactive_voter_with_bad_reporter_index_should_not_work() {
 			42,
 			2, (voter_ids().iter().position(|&i| i == 2).unwrap() as u32).into(),
 			2
-		), "invalid reporter index");
+		), Error::<Test>::InvalidReporterIndex);
 	});
 }
 
@@ -656,7 +656,7 @@ fn retracting_inactive_voter_with_bad_target_index_should_not_work() {
 			(voter_ids().iter().position(|&i| i == 2).unwrap() as u32).into(),
 			2, 42,
 			2
-		), "invalid target index");
+		), Error::<Test>::InvalidTargetIndex);
 	});
 }
 
@@ -733,7 +733,7 @@ fn retracting_inactive_voter_by_nonvoter_should_not_work() {
 			0,
 			2, (voter_ids().iter().position(|&i| i == 2).unwrap() as u32).into(),
 			2
-		), "reporter must be a voter");
+		), Error::<Test>::NotVoter);
 	});
 }
 
@@ -803,7 +803,7 @@ fn candidacy_submission_not_using_free_slot_should_not_work() {
 		System::set_block_number(1);
 		assert_noop!(
 			Elections::submit_candidacy(Origin::signed(4), 3),
-			"invalid candidate slot"
+			Error::<Test>::InvalidCandidateSlot
 		);
 	});
 }
@@ -815,7 +815,7 @@ fn candidacy_bad_candidate_slot_submission_should_not_work() {
 		assert_eq!(Elections::candidates(), Vec::<u64>::new());
 		assert_noop!(
 			Elections::submit_candidacy(Origin::signed(1), 1),
-			"invalid candidate slot"
+			Error::<Test>::InvalidCandidateSlot
 		);
 	});
 }
@@ -829,7 +829,7 @@ fn candidacy_non_free_candidate_slot_submission_should_not_work() {
 		assert_eq!(Elections::candidates(), vec![1]);
 		assert_noop!(
 			Elections::submit_candidacy(Origin::signed(2), 0),
-			"invalid candidate slot"
+			Error::<Test>::InvalidCandidateSlot
 		);
 	});
 }
@@ -843,7 +843,7 @@ fn candidacy_dupe_candidate_submission_should_not_work() {
 		assert_eq!(Elections::candidates(), vec![1]);
 		assert_noop!(
 			Elections::submit_candidacy(Origin::signed(1), 1),
-			"duplicate candidate submission"
+			Error::<Test>::DuplicatedCandidate,
 		);
 	});
 }
@@ -855,7 +855,7 @@ fn candidacy_poor_candidate_submission_should_not_work() {
 		assert_eq!(Elections::candidates(), Vec::<u64>::new());
 		assert_noop!(
 			Elections::submit_candidacy(Origin::signed(7), 0),
-			"candidate has not enough funds"
+			Error::<Test>::InsufficientCandidateFunds,
 		);
 	});
 }
@@ -1014,7 +1014,7 @@ fn election_presentations_with_zero_staked_deposit_should_not_work() {
 		System::set_block_number(6);
 		assert_noop!(
 			Elections::present_winner(Origin::signed(4), 2, 0, 0),
-			"stake deposited to present winner and be added to leaderboard should be non-zero"
+			Error::<Test>::ZeroDeposit,
 		);
 	});
 }
@@ -1036,7 +1036,7 @@ fn election_double_presentations_should_be_punished() {
 		assert_ok!(Elections::present_winner(Origin::signed(4), 5, 50, 0));
 		assert_eq!(
 			Elections::present_winner(Origin::signed(4), 5, 50, 0),
-			Err("duplicate presentation".into()),
+			Err(Error::<Test>::DuplicatedPresentation.into()),
 		);
 		assert_ok!(Elections::end_block(System::block_number()));
 
@@ -1067,7 +1067,7 @@ fn election_presenting_for_double_election_should_not_work() {
 		System::set_block_number(10);
 		assert_noop!(
 			Elections::present_winner(Origin::signed(4), 2, 20, 1),
-			"candidate must not form a duplicated member if elected"
+			Error::<Test>::DuplicatedCandidate,
 		);
 	});
 }
@@ -1101,7 +1101,7 @@ fn election_presenting_loser_should_not_work() {
 			(60, 1)
 		]));
 
-		assert_noop!(Elections::present_winner(Origin::signed(4), 2, 20, 0), "candidate not worthy of leaderboard");
+		assert_noop!(Elections::present_winner(Origin::signed(4), 2, 20, 0), Error::<Test>::UnworthyCandidate);
 	});
 }
 
@@ -1144,7 +1144,7 @@ fn election_present_outside_of_presentation_period_should_not_work() {
 		assert!(!Elections::presentation_active());
 		assert_noop!(
 			Elections::present_winner(Origin::signed(5), 5, 1, 0),
-			"cannot present outside of presentation period"
+			Error::<Test>::NotPresentationPeriod,
 		);
 	});
 }
@@ -1160,7 +1160,7 @@ fn election_present_with_invalid_vote_index_should_not_work() {
 		assert_ok!(Elections::end_block(System::block_number()));
 
 		System::set_block_number(6);
-		assert_noop!(Elections::present_winner(Origin::signed(4), 2, 20, 1), "index not current");
+		assert_noop!(Elections::present_winner(Origin::signed(4), 2, 20, 1), Error::<Test>::InvalidVoteIndex);
 	});
 }
 
@@ -1190,7 +1190,7 @@ fn election_present_when_presenter_is_poor_should_not_work() {
 				if p > 5 {
 					assert_noop!(Elections::present_winner(
 						Origin::signed(1), 1, 10, 0),
-						"presenter must have sufficient slashable funds"
+						Error::<Test>::InsufficientPresenterFunds,
 					);
 				} else {
 					assert_ok!(Elections::present_winner(Origin::signed(1), 1, 10, 0));
@@ -1215,7 +1215,7 @@ fn election_invalid_present_tally_should_slash() {
 		assert_ok!(Elections::end_block(System::block_number()));
 
 		System::set_block_number(6);
-		assert_err!(Elections::present_winner(Origin::signed(4), 2, 80, 0), "incorrect total");
+		assert_err!(Elections::present_winner(Origin::signed(4), 2, 80, 0), Error::<Test>::IncorrectTotal);
 
 		assert_eq!(Balances::total_balance(&4), 38);
 	});

substrate/frame/generic-asset/src/lib.rs

@@ -321,7 +321,7 @@ impl<AccountId> Into<PermissionVersions<AccountId>> for PermissionLatest<Account
 }
 
 decl_error! {
-	/// Error for the identity module.
+	/// Error for the generic-asset module.
 	pub enum Error for Module<T: Trait> {
 		/// No new assets id available.
 		NoIdAvailable,