Replace parachain/parathread boolean by enum (#6198)

* Replace parachain/parathread boolean by enum

* Address PR comments

* Update dependencies

* ParaType -> ParaKind

* Swap enum field order to avoid migration

* Rename paratype field to parakind

* Manual en-/decocing of Parakind

* Manual TypeInfo for ParaKind

* rename field back to parachain

* minor

* Update runtime/parachains/src/paras/mod.rs

Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com>

* Manual serde Serialize and Deserialize for ParaKind

* cargo fmt

* Update runtime/parachains/src/paras/mod.rs

Co-authored-by: Andronik <write@reusable.software>

* Add test for serde_json encoding/decoding

* Move serde_json dep to dev-deps

Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com>
Co-authored-by: Andronik <write@reusable.software>

polkadot/runtime/parachains/src/paras/mod.rs

@@ -115,7 +115,7 @@ use primitives::v2::{
 	ConsensusLog, HeadData, Id as ParaId, PvfCheckStatement, SessionIndex, UpgradeGoAhead,
 	UpgradeRestriction, ValidationCode, ValidationCodeHash, ValidatorSignature,
 };
-use scale_info::TypeInfo;
+use scale_info::{Type, TypeInfo};
 use sp_core::RuntimeDebug;
 use sp_runtime::{
 	traits::{AppVerify, One, Saturating},
@@ -291,8 +291,76 @@ pub struct ParaGenesisArgs {
 	pub genesis_head: HeadData,
 	/// The initial validation code to use.
 	pub validation_code: ValidationCode,
-	/// True if parachain, false if parathread.
-	pub parachain: bool,
+	/// Parachain or Parathread.
+	#[cfg_attr(feature = "std", serde(rename = "parachain"))]
+	pub para_kind: ParaKind,
+}
+
+/// Distinguishes between Parachain and Parathread
+#[derive(PartialEq, Eq, Clone, RuntimeDebug)]
+pub enum ParaKind {
+	Parathread,
+	Parachain,
+}
+
+#[cfg(feature = "std")]
+impl Serialize for ParaKind {
+	fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+	where
+		S: serde::Serializer,
+	{
+		match self {
+			ParaKind::Parachain => serializer.serialize_bool(true),
+			ParaKind::Parathread => serializer.serialize_bool(false),
+		}
+	}
+}
+
+#[cfg(feature = "std")]
+impl<'de> Deserialize<'de> for ParaKind {
+	fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+	where
+		D: serde::Deserializer<'de>,
+	{
+		match serde::de::Deserialize::deserialize(deserializer) {
+			Ok(true) => Ok(ParaKind::Parachain),
+			Ok(false) => Ok(ParaKind::Parathread),
+			_ => Err(serde::de::Error::custom("invalid ParaKind serde representation")),
+		}
+	}
+}
+
+// Manual encoding, decoding, and TypeInfo as the parakind field in ParaGenesisArgs used to be a bool
+impl Encode for ParaKind {
+	fn size_hint(&self) -> usize {
+		true.size_hint()
+	}
+
+	fn using_encoded<R, F: FnOnce(&[u8]) -> R>(&self, f: F) -> R {
+		match self {
+			ParaKind::Parachain => true.using_encoded(f),
+			ParaKind::Parathread => false.using_encoded(f),
+		}
+	}
+}
+
+impl Decode for ParaKind {
+	fn decode<I: parity_scale_codec::Input>(
+		input: &mut I,
+	) -> Result<Self, parity_scale_codec::Error> {
+		match bool::decode(input) {
+			Ok(true) => Ok(ParaKind::Parachain),
+			Ok(false) => Ok(ParaKind::Parathread),
+			_ => Err("Invalid ParaKind representation".into()),
+		}
+	}
+}
+
+impl TypeInfo for ParaKind {
+	type Identity = bool;
+	fn type_info() -> Type {
+		bool::type_info()
+	}
 }
 
 /// This enum describes a reason why a particular PVF pre-checking vote was initiated. When the
@@ -2021,11 +2089,12 @@ impl<T: Config> Pallet<T> {
 		id: ParaId,
 		genesis_data: &ParaGenesisArgs,
 	) {
-		if genesis_data.parachain {
-			parachains.add(id);
-			ParaLifecycles::<T>::insert(&id, ParaLifecycle::Parachain);
-		} else {
-			ParaLifecycles::<T>::insert(&id, ParaLifecycle::Parathread);
+		match genesis_data.para_kind {
+			ParaKind::Parachain => {
+				parachains.add(id);
+				ParaLifecycles::<T>::insert(&id, ParaLifecycle::Parachain);
+			},
+			ParaKind::Parathread => ParaLifecycles::<T>::insert(&id, ParaLifecycle::Parathread),
 		}
 
 		// HACK: see the notice in `schedule_para_initialize`.