allow governance body on parachain to have sovereign account (#1291)

The goal is to allow Fellowship on Collective chain to have a sovereign
account on Polkadot so that we can add it as an identity registrar. This
will allow Fellows origin to be able to provide judgements for
Fellowship members.

This currently allow any body on any parachain including non system
parachains to have sovereign account. I cannot think of any reason why
that may be an issue but let me know if I should change it to filter
only system parachains.

[This](https://gist.github.com/xlc/ec61bfa4e9f6d62da27d30141ad2c72b) is
the testing script.

Original PR: https://github.com/paritytech/polkadot/pull/7518

polkadot/runtime/kusama/src/xcm_config.rs

@@ -37,10 +37,11 @@ use xcm::latest::prelude::*;
 use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
 	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, ChildParachainAsNative,
-	ChildParachainConvertsVia, CurrencyAdapter as XcmCurrencyAdapter, IsChildSystemParachain,
-	IsConcrete, MintLocation, OriginToPluralityVoice, SignedAccountId32AsNative,
-	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId,
-	UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	ChildParachainConvertsVia, CurrencyAdapter as XcmCurrencyAdapter, DescribeBodyTerminal,
+	DescribeFamily, HashedDescription, IsChildSystemParachain, IsConcrete, MintLocation,
+	OriginToPluralityVoice, SignedAccountId32AsNative, SignedToAccountId32,
+	SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId, UsingComponents,
+	WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 };
 
 parameter_types! {
@@ -67,6 +68,8 @@ pub type SovereignAccountOf = (
 	ChildParachainConvertsVia<ParaId, AccountId>,
 	// We can directly alias an `AccountId32` into a local account.
 	AccountId32Aliases<ThisNetwork, AccountId>,
+	// Allow governance body to be used as a sovereign account.
+	HashedDescription<AccountId, DescribeFamily<DescribeBodyTerminal>>,
 );
 
 /// Our asset transactor. This is what allows us to interest with the runtime facilities from the

polkadot/runtime/polkadot/src/xcm_config.rs

@@ -40,10 +40,10 @@ use xcm::latest::prelude::*;
 use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
 	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, ChildParachainAsNative,
-	ChildParachainConvertsVia, CurrencyAdapter as XcmCurrencyAdapter, IsConcrete, MintLocation,
-	OriginToPluralityVoice, SignedAccountId32AsNative, SignedToAccountId32,
-	SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId, UsingComponents,
-	WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	ChildParachainConvertsVia, CurrencyAdapter as XcmCurrencyAdapter, DescribeBodyTerminal,
+	DescribeFamily, HashedDescription, IsConcrete, MintLocation, OriginToPluralityVoice,
+	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
+	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 };
 
 parameter_types! {
@@ -68,6 +68,8 @@ pub type SovereignAccountOf = (
 	ChildParachainConvertsVia<ParaId, AccountId>,
 	// We can directly alias an `AccountId32` into a local account.
 	AccountId32Aliases<ThisNetwork, AccountId>,
+	// Allow governance body to be used as a sovereign account.
+	HashedDescription<AccountId, DescribeFamily<DescribeBodyTerminal>>,
 );
 
 /// Our asset transactor. This is what allows us to interact with the runtime assets from the point

polkadot/runtime/rococo/src/xcm_config.rs

@@ -36,10 +36,11 @@ use xcm::latest::prelude::*;
 use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
 	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, ChildParachainAsNative,
-	ChildParachainConvertsVia, CurrencyAdapter as XcmCurrencyAdapter, FixedWeightBounds,
-	IsChildSystemParachain, IsConcrete, MintLocation, SignedAccountId32AsNative,
-	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId,
-	UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	ChildParachainConvertsVia, CurrencyAdapter as XcmCurrencyAdapter, DescribeBodyTerminal,
+	DescribeFamily, FixedWeightBounds, HashedDescription, IsChildSystemParachain, IsConcrete,
+	MintLocation, SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation,
+	TakeWeightCredit, TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin,
+	WithUniqueTopic,
 };
 use xcm_executor::XcmExecutor;
 
@@ -51,8 +52,14 @@ parameter_types! {
 	pub LocalCheckAccount: (AccountId, MintLocation) = (CheckAccount::get(), MintLocation::Local);
 }
 
-pub type LocationConverter =
-	(ChildParachainConvertsVia<ParaId, AccountId>, AccountId32Aliases<ThisNetwork, AccountId>);
+pub type LocationConverter = (
+	// We can convert a child parachain using the standard `AccountId` conversion.
+	ChildParachainConvertsVia<ParaId, AccountId>,
+	// We can directly alias an `AccountId32` into a local account.
+	AccountId32Aliases<ThisNetwork, AccountId>,
+	// Allow governance body to be used as a sovereign account.
+	HashedDescription<AccountId, DescribeFamily<DescribeBodyTerminal>>,
+);
 
 /// Our asset transactor. This is what allows us to interest with the runtime facilities from the
 /// point of view of XCM-only concepts like `MultiLocation` and `MultiAsset`.

polkadot/runtime/westend/src/xcm_config.rs

@@ -35,10 +35,10 @@ use xcm::latest::prelude::*;
 use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
 	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, ChildParachainAsNative,
-	ChildParachainConvertsVia, CurrencyAdapter as XcmCurrencyAdapter, IsChildSystemParachain,
-	IsConcrete, MintLocation, SignedAccountId32AsNative, SignedToAccountId32,
-	SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId, UsingComponents,
-	WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	ChildParachainConvertsVia, CurrencyAdapter as XcmCurrencyAdapter, DescribeBodyTerminal,
+	DescribeFamily, HashedDescription, IsChildSystemParachain, IsConcrete, MintLocation,
+	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
+	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 };
 use xcm_executor::XcmExecutor;
 
@@ -54,8 +54,14 @@ parameter_types! {
 	pub const BaseDeliveryFee: u128 = CENTS.saturating_mul(3);
 }
 
-pub type LocationConverter =
-	(ChildParachainConvertsVia<ParaId, AccountId>, AccountId32Aliases<ThisNetwork, AccountId>);
+pub type LocationConverter = (
+	// We can convert a child parachain using the standard `AccountId` conversion.
+	ChildParachainConvertsVia<ParaId, AccountId>,
+	// We can directly alias an `AccountId32` into a local account.
+	AccountId32Aliases<ThisNetwork, AccountId>,
+	// Allow governance body to be used as a sovereign account.
+	HashedDescription<AccountId, DescribeFamily<DescribeBodyTerminal>>,
+);
 
 pub type LocalAssetTransactor = XcmCurrencyAdapter<
 	// Use this currency:

polkadot/xcm/xcm-builder/src/lib.rs

@@ -32,8 +32,8 @@ pub use location_conversion::ForeignChainAliasAccount;
 pub use location_conversion::{
 	Account32Hash, AccountId32Aliases, AccountKey20Aliases, AliasesIntoAccountId32,
 	ChildParachainConvertsVia, DescribeAccountId32Terminal, DescribeAccountIdTerminal,
-	DescribeAccountKey20Terminal, DescribeAllTerminal, DescribeFamily, DescribeLocation,
-	DescribePalletTerminal, DescribeTerminus, GlobalConsensusConvertsFor,
+	DescribeAccountKey20Terminal, DescribeAllTerminal, DescribeBodyTerminal, DescribeFamily,
+	DescribeLocation, DescribePalletTerminal, DescribeTerminus, GlobalConsensusConvertsFor,
 	GlobalConsensusParachainConvertsFor, HashedDescription, ParentIsPreset,
 	SiblingParachainConvertsVia,
 };

polkadot/xcm/xcm-builder/src/location_conversion.rs

@@ -86,11 +86,22 @@ impl DescribeLocation for DescribeAccountKey20Terminal {
 
 pub type DescribeAccountIdTerminal = (DescribeAccountId32Terminal, DescribeAccountKey20Terminal);
 
+pub struct DescribeBodyTerminal;
+impl DescribeLocation for DescribeBodyTerminal {
+	fn describe_location(l: &MultiLocation) -> Option<Vec<u8>> {
+		match (l.parents, &l.interior) {
+			(0, X1(Plurality { id, part })) => Some((b"Body", id, part).encode()),
+			_ => return None,
+		}
+	}
+}
+
 pub type DescribeAllTerminal = (
 	DescribeTerminus,
 	DescribePalletTerminal,
 	DescribeAccountId32Terminal,
 	DescribeAccountKey20Terminal,
+	DescribeBodyTerminal,
 );
 
 pub struct DescribeFamily<DescribeInterior>(PhantomData<DescribeInterior>);