Implement serialization via parity's scale codec

Ideally, this would be generic. Unfortunately, the generic API serde 
doesn't natively support borsh, nor SCALE, and while there is a serde 
SCALE crate, it's old. While it may be complete, it's not worth working 
with.

While we could still grab bincode, and a variety of other formats, it 
wasn't worth it to go custom and for Serai, we'll be using SCALE almost 
everywhere anyways.

Cargo.lock

@@ -8870,6 +8870,7 @@ version = "0.1.0"
 dependencies = [
  "async-recursion",
  "async-trait",
+ "parity-scale-codec",
  "tokio",
 ]
 

substrate/tendermint/Cargo.toml

@@ -8,6 +8,8 @@ authors = ["Luke Parker <lukeparker5132@gmail.com>"]
 edition = "2021"
 
 [dependencies]
+parity-scale-codec = { version = "3.2", features = ["derive"] }
+
 async-recursion = "1.0"
 async-trait = "0.1"
 tokio = { version = "1", features = ["macros", "rt", "sync"] }

substrate/tendermint/src/ext.rs

@@ -1,15 +1,23 @@
 use core::{hash::Hash, fmt::Debug};
 use std::sync::Arc;
 
+use parity_scale_codec::{Encode, Decode};
+
 use crate::Message;
 
-pub trait ValidatorId: Send + Sync + Clone + Copy + PartialEq + Eq + Hash + Debug {}
-impl<V: Send + Sync + Clone + Copy + PartialEq + Eq + Hash + Debug> ValidatorId for V {}
+pub trait ValidatorId:
+  Send + Sync + Clone + Copy + PartialEq + Eq + Hash + Debug + Encode + Decode
+{
+}
+impl<V: Send + Sync + Clone + Copy + PartialEq + Eq + Hash + Debug + Encode + Decode> ValidatorId
+  for V
+{
+}
 
 // Type aliases which are distinct according to the type system
-#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, Encode, Decode)]
 pub struct BlockNumber(pub u32);
-#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, Encode, Decode)]
 pub struct Round(pub u16);
 
 pub trait SignatureScheme {
@@ -40,7 +48,7 @@ pub trait Weights: Send + Sync {
   fn proposer(&self, number: BlockNumber, round: Round) -> Self::ValidatorId;
 }
 
-#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Encode, Decode)]
 pub enum BlockError {
   // Invalid behavior entirely
   Fatal,
@@ -48,8 +56,8 @@ pub enum BlockError {
   Temporal,
 }
 
-pub trait Block: Send + Sync + Clone + PartialEq + Debug {
-  type Id: Send + Sync + Copy + Clone + PartialEq + Debug;
+pub trait Block: Send + Sync + Clone + PartialEq + Debug + Encode + Decode {
+  type Id: Send + Sync + Copy + Clone + PartialEq + Debug + Encode + Decode;
 
   fn id(&self) -> Self::Id;
 }

substrate/tendermint/src/lib.rs

@@ -4,6 +4,8 @@ use std::{
   collections::HashMap,
 };
 
+use parity_scale_codec::{Encode, Decode};
+
 use tokio::{
   task::{JoinHandle, yield_now},
   sync::{
@@ -18,14 +20,14 @@ use ext::*;
 mod message_log;
 use message_log::MessageLog;
 
-#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, Encode, Decode)]
 enum Step {
   Propose,
   Prevote,
   Precommit,
 }
 
-#[derive(Clone, PartialEq, Debug)]
+#[derive(Clone, PartialEq, Debug, Encode, Decode)]
 enum Data<B: Block> {
   Proposal(Option<Round>, B),
   Prevote(Option<B::Id>),
@@ -42,7 +44,7 @@ impl<B: Block> Data<B> {
   }
 }
 
-#[derive(Clone, PartialEq, Debug)]
+#[derive(Clone, PartialEq, Debug, Encode, Decode)]
 pub struct Message<V: ValidatorId, B: Block> {
   sender: V,
 
@@ -52,7 +54,7 @@ pub struct Message<V: ValidatorId, B: Block> {
   data: Data<B>,
 }
 
-#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Encode, Decode)]
 pub enum TendermintError<V: ValidatorId> {
   Malicious(V),
   Temporal,

substrate/tendermint/tests/ext.rs

@@ -1,5 +1,7 @@
 use std::sync::Arc;
 
+use parity_scale_codec::{Encode, Decode};
+
 use tokio::sync::RwLock;
 
 use tendermint_machine::{ext::*, Message, TendermintMachine, TendermintHandle};
@@ -45,7 +47,7 @@ impl Weights for TestWeights {
   }
 }
 
-#[derive(Clone, PartialEq, Debug)]
+#[derive(Clone, PartialEq, Debug, Encode, Decode)]
 struct TestBlock {
   id: TestBlockId,
   valid: Result<(), BlockError>,