Revert "grandpa: Use storage proofs for Grandpa authorities (#3734)" (#3983)

This reverts commit c0a1926704.

substrate/core/finality-grandpa/primitives/src/lib.rs

@@ -23,9 +23,9 @@ extern crate alloc;
 
 #[cfg(feature = "std")]
 use serde::Serialize;
-use codec::{Encode, Decode, Input, Codec};
+use codec::{Encode, Decode, Codec};
 use sr_primitives::{ConsensusEngineId, RuntimeDebug};
-use rstd::borrow::Cow;
+use client::decl_runtime_apis;
 use rstd::vec::Vec;
 
 mod app {
@@ -46,10 +46,6 @@ pub type AuthoritySignature = app::Signature;
 /// The `ConsensusEngineId` of GRANDPA.
 pub const GRANDPA_ENGINE_ID: ConsensusEngineId = *b"FRNK";
 
-/// The storage key for the current set of weighted Grandpa authorities.
-/// The value stored is an encoded VersionedAuthorityList.
-pub const GRANDPA_AUTHORITIES_KEY: &'static [u8] = b":grandpa_authorities";
-
 /// The weight of an authority.
 pub type AuthorityWeight = u64;
 
@@ -62,15 +58,12 @@ pub type SetId = u64;
 /// The round indicator.
 pub type RoundNumber = u64;
 
-/// A list of Grandpa authorities with associated weights.
-pub type AuthorityList = Vec<(AuthorityId, AuthorityWeight)>;
-
 /// A scheduled change of authority set.
 #[cfg_attr(feature = "std", derive(Serialize))]
 #[derive(Clone, Eq, PartialEq, Encode, Decode, RuntimeDebug)]
 pub struct ScheduledChange<N> {
 	/// The new authorities after the change, along with their respective weights.
-	pub next_authorities: AuthorityList,
+	pub next_authorities: Vec<(AuthorityId, AuthorityWeight)>,
 	/// The number of blocks to delay.
 	pub delay: N,
 }
@@ -161,51 +154,24 @@ pub const PENDING_CHANGE_CALL: &str = "grandpa_pending_change";
 /// WASM function call to get current GRANDPA authorities.
 pub const AUTHORITIES_CALL: &str = "grandpa_authorities";
 
-/// The current version of the stored AuthorityList type. The encoding version MUST be updated any
-/// time the AuthorityList type changes.
-const AUTHORITIES_VERISON: u8 = 1;
-
-/// An AuthorityList that is encoded with a version specifier. The encoding version is updated any
-/// time the AuthorityList type changes. This ensures that encodings of different versions of an
-/// AuthorityList are differentiable. Attempting to decode an authority list with an unknown
-/// version will fail.
-#[derive(Default)]
-pub struct VersionedAuthorityList<'a>(Cow<'a, AuthorityList>);
-
-impl<'a> From<AuthorityList> for VersionedAuthorityList<'a> {
-	fn from(authorities: AuthorityList) -> Self {
-		VersionedAuthorityList(Cow::Owned(authorities))
-	}
-}
-
-impl<'a> From<&'a AuthorityList> for VersionedAuthorityList<'a> {
-	fn from(authorities: &'a AuthorityList) -> Self {
-		VersionedAuthorityList(Cow::Borrowed(authorities))
-	}
-}
-
-impl<'a> Into<AuthorityList> for VersionedAuthorityList<'a> {
-	fn into(self) -> AuthorityList {
-		self.0.into_owned()
-	}
-}
-
-impl<'a> Encode for VersionedAuthorityList<'a> {
-	fn size_hint(&self) -> usize {
-		(AUTHORITIES_VERISON, self.0.as_ref()).size_hint()
-	}
-
-	fn using_encoded<R, F: FnOnce(&[u8]) -> R>(&self, f: F) -> R {
-		(AUTHORITIES_VERISON, self.0.as_ref()).using_encoded(f)
-	}
-}
-
-impl<'a> Decode for VersionedAuthorityList<'a> {
-	fn decode<I: Input>(value: &mut I) -> Result<Self, codec::Error> {
-		let (version, authorities): (u8, AuthorityList) = Decode::decode(value)?;
-		if version != AUTHORITIES_VERISON {
-			return Err("unknown Grandpa authorities version".into());
-		}
-		Ok(authorities.into())
+decl_runtime_apis! {
+	/// APIs for integrating the GRANDPA finality gadget into runtimes.
+	/// This should be implemented on the runtime side.
+	///
+	/// This is primarily used for negotiating authority-set changes for the
+	/// gadget. GRANDPA uses a signaling model of changing authority sets:
+	/// changes should be signaled with a delay of N blocks, and then automatically
+	/// applied in the runtime after those N blocks have passed.
+	///
+	/// The consensus protocol will coordinate the handoff externally.
+	#[api_version(2)]
+	pub trait GrandpaApi {
+		/// Get the current GRANDPA authorities and weights. This should not change except
+		/// for when changes are scheduled and the corresponding delay has passed.
+		///
+		/// When called at block B, it will return the set of authorities that should be
+		/// used to finalize descendants of this block (B+1, B+2, ...). The block B itself
+		/// is finalized by the authorities from block B-1.
+		fn grandpa_authorities() -> Vec<(AuthorityId, AuthorityWeight)>;
 	}
 }