Allow pallet's info to be enumerated (#10053)

* Allow pallet's info to be enumerated

* Fixes

* Formatting

* Flat tuple for getting all pallet instances

* Renaming and fixing reversedness

* Formatting

* Fixes

* Back to nesting

* Back to nestingx

* Revert executive lib

* Reversions

* Reversions

* Fixes

* Fixes

* Formatting

* Fixes

* Spelling

* Comments

substrate/frame/support/src/traits/metadata.rs

@@ -19,6 +19,7 @@
 
 use codec::{Decode, Encode};
 use sp_runtime::RuntimeDebug;
+use sp_std::prelude::*;
 
 /// Provides information about the pallet itself and its setup in the runtime.
 ///
@@ -35,6 +36,19 @@ pub trait PalletInfo {
 	fn crate_version<P: 'static>() -> Option<CrateVersion>;
 }
 
+/// Information regarding an instance of a pallet.
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, RuntimeDebug)]
+pub struct PalletInfoData {
+	/// Index of the pallet as configured in the runtime.
+	pub index: usize,
+	/// Name of the pallet as configured in the runtime.
+	pub name: &'static str,
+	/// Name of the Rust module containing the pallet.
+	pub module_name: &'static str,
+	/// Version of the crate containing the pallet.
+	pub crate_version: CrateVersion,
+}
+
 /// Provides information about the pallet itself and its setup in the runtime.
 ///
 /// Declare some information and access the information provided by [`PalletInfo`] for a specific
@@ -50,6 +64,49 @@ pub trait PalletInfoAccess {
 	fn crate_version() -> CrateVersion;
 }
 
+/// Provide information about a bunch of pallets.
+pub trait PalletsInfoAccess {
+	/// The number of pallets' information that this type represents.
+	///
+	/// You probably don't want this function but `infos()` instead.
+	fn count() -> usize {
+		0
+	}
+
+	/// Extend the given vector by all of the pallets' information that this type represents.
+	///
+	/// You probably don't want this function but `infos()` instead.
+	fn accumulate(_accumulator: &mut Vec<PalletInfoData>) {}
+
+	/// All of the pallets' information that this type represents.
+	fn infos() -> Vec<PalletInfoData> {
+		let mut result = Vec::with_capacity(Self::count());
+		Self::accumulate(&mut result);
+		result
+	}
+}
+
+impl PalletsInfoAccess for () {}
+impl<T: PalletsInfoAccess> PalletsInfoAccess for (T,) {
+	fn count() -> usize {
+		T::count()
+	}
+	fn accumulate(acc: &mut Vec<PalletInfoData>) {
+		T::accumulate(acc)
+	}
+}
+
+impl<T1: PalletsInfoAccess, T2: PalletsInfoAccess> PalletsInfoAccess for (T1, T2) {
+	fn count() -> usize {
+		T1::count() + T2::count()
+	}
+	fn accumulate(acc: &mut Vec<PalletInfoData>) {
+		// The AllPallets type tuplises the pallets in reverse order, so we unreverse them here.
+		T2::accumulate(acc);
+		T1::accumulate(acc);
+	}
+}
+
 /// The function and pallet name of the Call.
 #[derive(Clone, Eq, PartialEq, Default, RuntimeDebug)]
 pub struct CallMetadata {
@@ -206,6 +263,37 @@ pub trait GetStorageVersion {
 mod tests {
 	use super::*;
 
+	struct Pallet1;
+	impl PalletInfoAccess for Pallet1 {
+		fn index() -> usize {
+			1
+		}
+		fn name() -> &'static str {
+			"Pallet1"
+		}
+		fn module_name() -> &'static str {
+			"pallet1"
+		}
+		fn crate_version() -> CrateVersion {
+			CrateVersion::new(1, 0, 0)
+		}
+	}
+	struct Pallet2;
+	impl PalletInfoAccess for Pallet2 {
+		fn index() -> usize {
+			2
+		}
+		fn name() -> &'static str {
+			"Pallet2"
+		}
+		fn module_name() -> &'static str {
+			"pallet2"
+		}
+		fn crate_version() -> CrateVersion {
+			CrateVersion::new(1, 0, 0)
+		}
+	}
+
 	#[test]
 	fn check_storage_version_ordering() {
 		let version = StorageVersion::new(1);