More decl_error! migrations (#4427)

* Update assets to `decl_error`

* Update aura to `decl_error`

* Update authority discovery to `decl_error`

* Update collective to `decl_error`

* Update evm to `decl_error!`

* Fix error with replace

* Revert "Update authority discovery to `decl_error`"

This reverts commit 26e8f3c56656963d847e984c6f2c8e1f88014899.

* Revert "Update aura to `decl_error`"

This reverts commit 8f17c44ca8375a4a755710aaab7ad4d9522c4376.

* Update democracy to `decl_error`

* Update finality-tracker to `decl_error`

* Update grandpa to `decl_error`

* `assert` to `ensure` in dispatchable function

substrate/frame/grandpa/src/lib.rs

@@ -31,10 +31,12 @@
 pub use sp_finality_grandpa as fg_primitives;
 
 use sp_std::prelude::*;
-use codec::{self as codec, Encode, Decode, Error};
-use frame_support::{decl_event, decl_storage, decl_module, dispatch, storage};
+use codec::{self as codec, Encode, Decode};
+use frame_support::{decl_event, decl_storage, decl_module, decl_error, storage};
 use sp_runtime::{
-	generic::{DigestItem, OpaqueDigestItemId}, traits::Zero, Perbill,
+	generic::{DigestItem, OpaqueDigestItemId},
+	traits::{Zero, ModuleDispatchError},
+	Perbill,
 };
 use sp_staking::{
 	SessionIndex,
@@ -82,7 +84,7 @@ pub struct StoredPendingChange<N> {
 }
 
 impl<N: Decode> Decode for StoredPendingChange<N> {
-	fn decode<I: codec::Input>(value: &mut I) -> core::result::Result<Self, Error> {
+	fn decode<I: codec::Input>(value: &mut I) -> core::result::Result<Self, codec::Error> {
 		let old = OldStoredPendingChange::decode(value)?;
 		let forced = <Option<N>>::decode(value).unwrap_or(None);
 
@@ -123,7 +125,7 @@ pub enum StoredState<N> {
 	},
 }
 
-decl_event!(
+decl_event! {
 	pub enum Event {
 		/// New authority set has been applied.
 		NewAuthorities(AuthorityList),
@@ -132,7 +134,22 @@ decl_event!(
 		/// Current authority set has been resumed.
 		Resumed,
 	}
-);
+}
+
+decl_error! {
+	pub enum Error {
+		/// Attempt to signal GRANDPA pause when the authority set isn't live
+		/// (either paused or already pending pause).
+		PauseFailed,
+		/// Attempt to signal GRANDPA resume when the authority set isn't paused
+		/// (either live or already pending resume).
+		ResumeFailed,
+		/// Attempt to signal GRANDPA change with one already pending.
+		ChangePending,
+		/// Cannot signal forced change so soon after last.
+		TooSoon,
+	}
+}
 
 decl_storage! {
 	trait Store for Module<T: Trait> as GrandpaFinality {
@@ -170,11 +187,13 @@ decl_storage! {
 
 decl_module! {
 	pub struct Module<T: Trait> for enum Call where origin: T::Origin {
+		type Error = Error;
+
 		fn deposit_event() = default;
 
 		/// Report some misbehavior.
 		fn report_misbehavior(origin, _report: Vec<u8>) {
-			ensure_signed(origin)?;
+			ensure_signed(origin).map_err(|e| e.as_str())?;
 			// FIXME: https://github.com/paritytech/substrate/issues/1112
 		}
 
@@ -264,7 +283,7 @@ impl<T: Trait> Module<T> {
 
 	/// Schedule GRANDPA to pause starting in the given number of blocks.
 	/// Cannot be done when already paused.
-	pub fn schedule_pause(in_blocks: T::BlockNumber) -> dispatch::Result {
+	pub fn schedule_pause(in_blocks: T::BlockNumber) -> Result<(), Error> {
 		if let StoredState::Live = <State<T>>::get() {
 			let scheduled_at = <frame_system::Module<T>>::block_number();
 			<State<T>>::put(StoredState::PendingPause {
@@ -274,13 +293,12 @@ impl<T: Trait> Module<T> {
 
 			Ok(())
 		} else {
-			Err("Attempt to signal GRANDPA pause when the authority set isn't live \
-				(either paused or already pending pause).")
+			Err(Error::PauseFailed)
 		}
 	}
 
 	/// Schedule a resume of GRANDPA after pausing.
-	pub fn schedule_resume(in_blocks: T::BlockNumber) -> dispatch::Result {
+	pub fn schedule_resume(in_blocks: T::BlockNumber) -> Result<(), Error> {
 		if let StoredState::Paused = <State<T>>::get() {
 			let scheduled_at = <frame_system::Module<T>>::block_number();
 			<State<T>>::put(StoredState::PendingResume {
@@ -290,8 +308,7 @@ impl<T: Trait> Module<T> {
 
 			Ok(())
 		} else {
-			Err("Attempt to signal GRANDPA resume when the authority set isn't paused \
-				(either live or already pending resume).")
+			Err(Error::ResumeFailed)
 		}
 	}
 
@@ -313,13 +330,13 @@ impl<T: Trait> Module<T> {
 		next_authorities: AuthorityList,
 		in_blocks: T::BlockNumber,
 		forced: Option<T::BlockNumber>,
-	) -> dispatch::Result {
+	) -> Result<(), Error> {
 		if !<PendingChange<T>>::exists() {
 			let scheduled_at = <frame_system::Module<T>>::block_number();
 
 			if let Some(_) = forced {
 				if Self::next_forced().map_or(false, |next| next > scheduled_at) {
-					return Err("Cannot signal forced change so soon after last.");
+					return Err(Error::TooSoon);
 				}
 
 				// only allow the next forced change when twice the window has passed since
@@ -336,7 +353,7 @@ impl<T: Trait> Module<T> {
 
 			Ok(())
 		} else {
-			Err("Attempt to signal GRANDPA change with one already pending.")
+			Err(Error::ChangePending)
 		}
 	}