Make pallet macro generate accessor to PalletInfo information on pallet placeholder (#8630)

* generate accessor to PalletInfo information on pallet placeholder

* remove unused

* use trait, and add tests

* less verbose doc

* add PalletInfoAccess to prelude for ease usage

substrate/frame/support/src/lib.rs

@@ -1234,7 +1234,7 @@ pub mod pallet_prelude {
 		EqNoBound, PartialEqNoBound, RuntimeDebugNoBound, DebugNoBound, CloneNoBound, Twox256,
 		Twox128, Blake2_256, Blake2_128, Identity, Twox64Concat, Blake2_128Concat, ensure,
 		RuntimeDebug, storage,
-		traits::{Get, Hooks, IsType, GetPalletVersion, EnsureOrigin},
+		traits::{Get, Hooks, IsType, GetPalletVersion, EnsureOrigin, PalletInfoAccess},
 		dispatch::{DispatchResultWithPostInfo, Parameter, DispatchError, DispatchResult},
 		weights::{DispatchClass, Pays, Weight},
 		storage::types::{StorageValue, StorageMap, StorageDoubleMap, ValueQuery, OptionQuery},
@@ -1362,6 +1362,10 @@ pub mod pallet_prelude {
 ///
 /// It declare `type Module` type alias for `Pallet`, used by [`construct_runtime`].
 ///
+/// It implements [`traits::PalletInfoAccess`] on `Pallet` to ease access to pallet informations
+/// given by [`frame_support::traits::PalletInfo`].
+/// (The implementation use the associated type `frame_system::Config::PalletInfo`).
+///
 /// If attribute generate_store then macro create the trait `Store` and implement it on `Pallet`.
 ///
 /// # Hooks: `#[pallet::hooks]` mandatory

substrate/frame/support/src/traits.rs

@@ -61,7 +61,7 @@ pub use randomness::Randomness;
 mod metadata;
 pub use metadata::{
 	CallMetadata, GetCallMetadata, GetCallName, PalletInfo, PalletVersion, GetPalletVersion,
-	PALLET_VERSION_STORAGE_KEY_POSTFIX,
+	PALLET_VERSION_STORAGE_KEY_POSTFIX, PalletInfoAccess,
 };
 
 mod hooks;

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

@@ -31,6 +31,16 @@ pub trait PalletInfo {
 	fn name<P: 'static>() -> Option<&'static str>;
 }
 
+/// Provides information about the pallet setup in the runtime.
+///
+/// Access the information provided by [`PalletInfo`] for a specific pallet.
+pub trait PalletInfoAccess {
+	/// Index of the pallet as configured in the runtime.
+	fn index() -> usize;
+	/// Name of the pallet as configured in the runtime.
+	fn name() -> &'static str;
+}
+
 /// The function and pallet name of the Call.
 #[derive(Clone, Eq, PartialEq, Default, RuntimeDebug)]
 pub struct CallMetadata {