Adds ability to provide defaults for types provided by construct_runtime

frame/examples/default-config/src/lib.rs

@@ -107,7 +107,6 @@ pub mod pallet {
 pub mod tests {
 	use super::*;
 	use frame_support::derive_impl;
-	use sp_runtime::traits::ConstU64;
 
 	use super::pallet as pallet_default_config_example;
 
@@ -126,14 +125,6 @@ pub mod tests {
 		// these items are defined by frame-system as `no_default`, so we must specify them here.
 		// Note that these are types that actually rely on the outer runtime, and can't sensibly
 		// have an _independent_ default.
-		type Block = Block;
-		type BlockHashCount = ConstU64<10>;
-		type BaseCallFilter = frame_support::traits::Everything;
-		type RuntimeOrigin = RuntimeOrigin;
-		type RuntimeCall = RuntimeCall;
-		type RuntimeEvent = RuntimeEvent;
-		type PalletInfo = PalletInfo;
-		type OnSetCode = ();
 
 		// all of this is coming from `frame_system::config_preludes::TestDefaultConfig`.
 

frame/support/procedural/src/derive_impl.rs

@@ -22,7 +22,48 @@ use macro_magic::mm_core::ForeignPath;
 use proc_macro2::TokenStream as TokenStream2;
 use quote::{quote, ToTokens};
 use std::collections::HashSet;
-use syn::{parse2, parse_quote, spanned::Spanned, Ident, ImplItem, ItemImpl, Path, Result, Token};
+use syn::{
+	parse2, parse_quote, spanned::Spanned, token, Ident, ImplItem, ItemImpl, Path, Result, Token,
+};
+
+mod keyword {
+	syn::custom_keyword!(pallet);
+	syn::custom_keyword!(verbatim);
+}
+
+#[derive(derive_syn_parse::Parse, PartialEq, Eq)]
+pub enum PalletAttrType {
+	#[peek(keyword::verbatim, name = "verbatim")]
+	Verbatim(keyword::verbatim),
+}
+
+#[derive(derive_syn_parse::Parse)]
+pub struct PalletAttr {
+	_pound: Token![#],
+	#[bracket]
+	_bracket: token::Bracket,
+	#[inside(_bracket)]
+	_pallet: keyword::pallet,
+	#[prefix(Token![::] in _bracket)]
+	#[inside(_bracket)]
+	typ: PalletAttrType,
+}
+
+fn take_first_item_pallet_attr<Attr>(item: &mut syn::ImplItemType) -> syn::Result<Option<Attr>>
+where
+	Attr: syn::parse::Parse,
+{
+	let attrs = &mut item.attrs;
+
+	if let Some(index) = attrs.iter().position(|attr| {
+		attr.path().segments.first().map_or(false, |segment| segment.ident == "pallet")
+	}) {
+		let pallet_attr = attrs.remove(index);
+		Ok(Some(syn::parse2(pallet_attr.into_token_stream())?))
+	} else {
+		Ok(None)
+	}
+}
 
 #[derive(Parse)]
 pub struct DeriveImplAttrArgs {
@@ -96,7 +137,19 @@ fn combine_impls(
 				// do not copy colliding items that have an ident
 				return None
 			}
-			if matches!(item, ImplItem::Type(_)) {
+			if let ImplItem::Type(item) = item.clone() {
+				let mut item = item.clone();
+				if let Ok(Some(pallet_attr)) = take_first_item_pallet_attr::<PalletAttr>(&mut item)
+				{
+					match pallet_attr.typ {
+						PalletAttrType::Verbatim(_) => {
+							let modified_item: ImplItem = parse_quote! {
+								type #ident = #ident;
+							};
+							return Some(modified_item)
+						},
+					}
+				}
 				// modify and insert uncolliding type items
 				let modified_item: ImplItem = parse_quote! {
 					type #ident = <#default_impl_path as #disambiguation_path>::#ident;

frame/support/procedural/src/lib.rs

@@ -1004,6 +1004,16 @@ pub fn no_default(_: TokenStream, _: TokenStream) -> TokenStream {
 	pallet_macro_stub()
 }
 
+#[proc_macro_attribute]
+pub fn no_bounds(_: TokenStream, _: TokenStream) -> TokenStream {
+	pallet_macro_stub()
+}
+
+#[proc_macro_attribute]
+pub fn verbatim(_: TokenStream, tokens: TokenStream) -> TokenStream {
+	tokens
+}
+
 /// Attach this attribute to an impl statement that you want to use with
 /// [`#[derive_impl(..)]`](`macro@derive_impl`).
 ///

frame/support/procedural/src/pallet/expand/config.rs

@@ -51,7 +51,23 @@ Consequently, a runtime that wants to include this pallet must implement this tr
 	// we only emit `DefaultConfig` if there are trait items, so an empty `DefaultConfig` is
 	// impossible consequently
 	if config.default_sub_trait.len() > 0 {
-		let trait_items = &config.default_sub_trait;
+		let trait_items = &config
+			.default_sub_trait
+			.iter()
+			.map(|item| {
+				if item.1 {
+					if let syn::TraitItem::Type(item) = item.0.clone() {
+						let mut item = item.clone();
+						item.bounds.clear();
+						syn::TraitItem::Type(item)
+					} else {
+						item.0.clone()
+					}
+				} else {
+					item.0.clone()
+				}
+			})
+			.collect::<Vec<_>>();
 		quote!(
 			/// Based on [`Config`]. Auto-generated by
 			/// [`#[pallet::config(with_default)]`](`frame_support::pallet_macros::config`).

frame/support/procedural/src/pallet/parse/config.rs

@@ -34,6 +34,7 @@ mod keyword {
 	syn::custom_keyword!(frame_system);
 	syn::custom_keyword!(disable_frame_system_supertrait_check);
 	syn::custom_keyword!(no_default);
+	syn::custom_keyword!(no_bounds);
 	syn::custom_keyword!(constant);
 }
 
@@ -59,7 +60,7 @@ pub struct ConfigDef {
 	/// Contains default sub-trait items (instantiated by `#[pallet::config(with_default)]`).
 	/// Vec will be empty if `#[pallet::config(with_default)]` is not specified or if there are
 	/// no trait items
-	pub default_sub_trait: Vec<syn::TraitItem>,
+	pub default_sub_trait: Vec<(syn::TraitItem, bool)>,
 }
 
 /// Input definition for a constant in pallet config.
@@ -136,6 +137,8 @@ impl syn::parse::Parse for DisableFrameSystemSupertraitCheck {
 pub enum PalletAttrType {
 	#[peek(keyword::no_default, name = "no_default")]
 	NoDefault(keyword::no_default),
+	#[peek(keyword::no_bounds, name = "no_bounds")]
+	NoBounds(keyword::no_bounds),
 	#[peek(keyword::constant, name = "constant")]
 	Constant(keyword::constant),
 }
@@ -348,6 +351,7 @@ impl ConfigDef {
 
 			let mut already_no_default = false;
 			let mut already_constant = false;
+			let mut already_no_bounds = false;
 
 			while let Ok(Some(pallet_attr)) =
 				helper::take_first_item_pallet_attr::<PalletAttr>(trait_item)
@@ -384,11 +388,27 @@ impl ConfigDef {
 						}
 						already_no_default = true;
 					},
+					(PalletAttrType::NoBounds(_), _) => {
+						if !enable_default {
+							return Err(syn::Error::new(
+								pallet_attr._bracket.span.join(),
+								"`#[pallet:no_bounds]` can only be used if `#[pallet::config(with_default)]` \
+								has been specified"
+							))
+						}
+						if already_no_bounds {
+							return Err(syn::Error::new(
+								pallet_attr._bracket.span.join(),
+								"Duplicate #[pallet::no_bounds] attribute not allowed.",
+							))
+						}
+						already_no_bounds = true;
+					},
 				}
 			}
 
-			if !already_no_default && !is_event && enable_default {
-				default_sub_trait.push(trait_item.clone());
+			if !already_no_default && enable_default {
+				default_sub_trait.push((trait_item.clone(), already_no_bounds));
 			}
 		}
 

frame/support/src/lib.rs

@@ -2905,8 +2905,8 @@ pub mod pallet_macros {
 		call_index, compact, composite_enum, config, constant,
 		disable_frame_system_supertrait_check, error, event, extra_constants, generate_deposit,
 		generate_store, genesis_build, genesis_config, getter, hooks, import_section, inherent,
-		no_default, origin, pallet_section, storage, storage_prefix, storage_version, type_value,
-		unbounded, validate_unsigned, weight, whitelist_storage,
+		no_bounds, no_default, origin, pallet_section, storage, storage_prefix, storage_version,
+		type_value, unbounded, validate_unsigned, verbatim, weight, whitelist_storage,
 	};
 }
 

frame/system/src/lib.rs

@@ -205,7 +205,8 @@ pub mod pallet {
 
 	/// Contains default types suitable for various environments
 	pub mod config_preludes {
-		use super::DefaultConfig;
+		use super::*;
+		use sp_runtime::traits::ConstU64;
 
 		/// Provides a viable default config that can be used with
 		/// [`derive_impl`](`frame_support::derive_impl`) to derive a testing pallet config
@@ -232,6 +233,19 @@ pub mod pallet {
 			type BlockWeights = ();
 			type BlockLength = ();
 			type DbWeight = ();
+			#[pallet::verbatim]
+			type RuntimeEvent = ();
+			#[pallet::verbatim]
+			type RuntimeOrigin = ();
+			#[pallet::verbatim]
+			type RuntimeCall = ();
+			#[pallet::verbatim]
+			type Block = ();
+			#[pallet::verbatim]
+			type PalletInfo = ();
+			type BaseCallFilter = frame_support::traits::Everything;
+			type BlockHashCount = ConstU64<10>;
+			type OnSetCode = ();
 		}
 	}
 
@@ -240,6 +254,7 @@ pub mod pallet {
 	#[pallet::disable_frame_system_supertrait_check]
 	pub trait Config: 'static + Eq + Clone {
 		/// The aggregated event type of the runtime.
+		#[pallet::no_bounds]
 		type RuntimeEvent: Parameter
 			+ Member
 			+ From<Event<Self>>
@@ -248,7 +263,7 @@ pub mod pallet {
 
 		/// The basic call filter to use in Origin. All origins are built with this filter as base,
 		/// except Root.
-		#[pallet::no_default]
+		#[pallet::no_bounds]
 		type BaseCallFilter: Contains<Self::RuntimeCall>;
 
 		/// Block & extrinsics weights: base values and limits.
@@ -260,14 +275,14 @@ pub mod pallet {
 		type BlockLength: Get<limits::BlockLength>;
 
 		/// The `RuntimeOrigin` type used by dispatchable calls.
-		#[pallet::no_default]
+		#[pallet::no_bounds]
 		type RuntimeOrigin: Into<Result<RawOrigin<Self::AccountId>, Self::RuntimeOrigin>>
 			+ From<RawOrigin<Self::AccountId>>
 			+ Clone
 			+ OriginTrait<Call = Self::RuntimeCall, AccountId = Self::AccountId>;
 
 		/// The aggregated `RuntimeCall` type.
-		#[pallet::no_default]
+		#[pallet::no_bounds]
 		type RuntimeCall: Parameter
 			+ Dispatchable<RuntimeOrigin = Self::RuntimeOrigin>
 			+ Debug
@@ -322,12 +337,12 @@ pub mod pallet {
 
 		/// The Block type used by the runtime. This is used by `construct_runtime` to retrieve the
 		/// extrinsics or other block specific data as needed.
-		#[pallet::no_default]
+		#[pallet::no_bounds]
 		type Block: Parameter + Member + traits::Block<Hash = Self::Hash>;
 
 		/// Maximum number of block number to block hash mappings to keep (oldest pruned first).
 		#[pallet::constant]
-		#[pallet::no_default]
+		#[pallet::no_bounds]
 		type BlockHashCount: Get<BlockNumberFor<Self>>;
 
 		/// The weight of runtime database operations the runtime can invoke.
@@ -344,7 +359,7 @@ pub mod pallet {
 		/// runtime.
 		///
 		/// For tests it is okay to use `()` as type, however it will provide "useless" data.
-		#[pallet::no_default]
+		#[pallet::no_bounds]
 		type PalletInfo: PalletInfo;
 
 		/// Data to be associated with an account (other than nonce/transaction counter, which this
@@ -376,7 +391,7 @@ pub mod pallet {
 		/// [`Pallet::update_code_in_storage`]).
 		/// It's unlikely that this needs to be customized, unless you are writing a parachain using
 		/// `Cumulus`, where the actual code change is deferred.
-		#[pallet::no_default]
+		#[pallet::no_bounds]
 		type OnSetCode: SetCode<Self>;
 
 		/// The maximum number of consumers allowed on a single account.