Abstract away the executive

bin/node-template/runtime/src/lib.rs

@@ -280,7 +280,8 @@ impl pallet_template::Config for Runtime {
 
 // Create the runtime by composing the FRAME pallets that were previously configured.
 construct_runtime!(
-	pub struct Runtime<_> {
+	type Migrations = ();
+	pub struct Runtime {
 		System: frame_system,
 		Timestamp: pallet_timestamp,
 		Aura: pallet_aura,

bin/node/runtime/src/lib.rs

@@ -1874,7 +1874,14 @@ impl pallet_statement::Config for Runtime {
 }
 
 construct_runtime!(
-	pub struct Runtime<Migrations>
+	// All migrations executed on runtime upgrade as a nested tuple of types implementing
+	// `OnRuntimeUpgrade`.
+	type Migrations = (
+		pallet_nomination_pools::migration::v2::MigrateToV2<Runtime>,
+		pallet_alliance::migration::Migration<Runtime>,
+		pallet_contracts::Migration<Runtime>,
+	);
+	pub struct Runtime
 	{
 		System: frame_system,
 		Utility: pallet_utility,
@@ -1983,14 +1990,6 @@ pub type SignedPayload = generic::SignedPayload<RuntimeCall, SignedExtra>;
 /// Extrinsic type that has already been checked.
 pub type CheckedExtrinsic = generic::CheckedExtrinsic<AccountId, RuntimeCall, SignedExtra>;
 
-// All migrations executed on runtime upgrade as a nested tuple of types implementing
-// `OnRuntimeUpgrade`.
-type Migrations = (
-	pallet_nomination_pools::migration::v2::MigrateToV2<Runtime>,
-	pallet_alliance::migration::Migration<Runtime>,
-	pallet_contracts::Migration<Runtime>,
-);
-
 type EventRecord = frame_system::EventRecord<
 	<Runtime as frame_system::Config>::RuntimeEvent,
 	<Runtime as frame_system::Config>::Hash,

frame/support/procedural/src/construct_runtime/expand/executive.rs

@@ -30,8 +30,8 @@ pub fn expand_executive(
 ) -> Result<TokenStream> {
 	let executive = generate_crate_access_2018("frame-executive")?;
 
-	let on_runtime_upgrade = match executive_section.custom_on_runtime_upgrade {
-		Some(custom) => quote!(#custom),
+	let migrations = match executive_section.migration_section {
+		Some(migrations) => quote!(#migrations),
 		None => quote!(()),
 	};
 
@@ -67,7 +67,7 @@ pub fn expand_executive(
 			#system::ChainContext<#runtime>,
 			#runtime,
 			AllPalletsWithSystem,
-			#on_runtime_upgrade
+			(#migrations)
 		>;
 
 		impl #runtime {

frame/support/procedural/src/construct_runtime/parse.rs

@@ -24,7 +24,7 @@ use syn::{
 	parse::{Parse, ParseStream},
 	punctuated::Punctuated,
 	spanned::Spanned,
-	token, Attribute, Error, Ident, Path, Result, Token,
+	token, Attribute, Error, Ident, Path, Result, Token, Type,
 };
 
 mod keyword {
@@ -82,6 +82,8 @@ pub struct ExplicitRuntimeDeclaration {
 
 impl Parse for RuntimeDeclaration {
 	fn parse(input: ParseStream) -> Result<Self> {
+		let executive_section = if input.peek(Token![type]) { Some(input.parse()?) } else { None };
+
 		input.parse::<Token![pub]>()?;
 
 		// Support either `enum` or `struct`.
@@ -93,8 +95,6 @@ impl Parse for RuntimeDeclaration {
 
 		let name = input.parse::<syn::Ident>()?;
 
-		let executive_section = if input.peek(Token![<]) { Some(input.parse()?) } else { None };
-
 		let where_section = if input.peek(token::Where) { Some(input.parse()?) } else { None };
 		let pallets =
 			input.parse::<ext::Braces<ext::Punctuated<PalletDeclaration, Token![,]>>>()?;
@@ -131,20 +131,65 @@ impl Parse for RuntimeDeclaration {
 #[derive(Debug)]
 pub struct ExecutiveSection {
 	pub span: Span,
-	pub custom_on_runtime_upgrade: Option<Ident>,
+	pub migration_section: Option<Migrations>,
 }
 
 impl Parse for ExecutiveSection {
 	fn parse(input: ParseStream) -> Result<Self> {
-		let _ = input.parse::<Token![<]>()?;
-		let custom_on_runtime_upgrade = if input.peek(Token![_]) {
-			let _ = input.parse::<Token![_]>()?;
-			None
+		let _ = input.parse::<Token![type]>()?;
+		let name = input.parse::<syn::Ident>()?;
+
+		let migration_section = if name.to_string() == "Migrations" {
+			Some(input.parse::<Migrations>()?)
 		} else {
-			Some(input.parse::<syn::Ident>()?)
+			None
 		};
-		let _ = input.parse::<Token![>]>()?;
-		Ok(Self { span: input.span(), custom_on_runtime_upgrade })
+
+		Ok(Self { span: input.span(), migration_section })
+	}
+}
+
+#[derive(Debug)]
+pub struct Migrations {
+	pub span: Span,
+	pub migrations: Punctuated<Migration, token::Comma>,
+}
+
+impl Parse for Migrations {
+	fn parse(input: ParseStream) -> Result<Self> {
+		let _ = input.parse::<Token![=]>()?;
+
+		let content;
+		syn::parenthesized!(content in input);
+
+		let migrations = content.parse_terminated(Migration::parse, Token![,])?;
+		let _ = input.parse::<Token![;]>()?;
+		Ok(Self { span: input.span(), migrations })
+	}
+}
+
+impl ToTokens for Migrations {
+	fn to_tokens(&self, tokens: &mut TokenStream) {
+		self.migrations.to_tokens(tokens);
+	}
+}
+
+#[derive(Debug)]
+pub struct Migration {
+	pub span: Span,
+	pub ident: Type,
+}
+
+impl Parse for Migration {
+	fn parse(input: ParseStream) -> Result<Self> {
+		let name = input.parse::<Type>()?;
+		Ok(Self { span: input.span(), ident: name })
+	}
+}
+
+impl ToTokens for Migration {
+	fn to_tokens(&self, tokens: &mut TokenStream) {
+		self.ident.to_tokens(tokens);
 	}
 }
 

frame/support/test/tests/construct_runtime_ui/invalid_migration_param.rs

@@ -17,7 +17,8 @@ impl frame_system::Config for Runtime {
 struct Dummy;
 
 construct_runtime! {
-	pub struct Runtime<Dummy>
+	type Migrations = (Dummy);
+	pub struct Runtime
 	{
 		System: frame_system
 	}

frame/support/test/tests/construct_runtime_ui/invalid_migration_param.stderr

@@ -8,11 +8,12 @@ error[E0599]: the function or associated item `execute_block` exists for struct
    |  __^
    | | _|
    | ||
-20 | ||     pub struct Runtime<Dummy>
-21 | ||     {
-22 | ||         System: frame_system
-23 | ||     }
-24 | || }
+20 | ||     type Migrations = (Dummy);
+21 | ||     pub struct Runtime
+22 | ||     {
+23 | ||         System: frame_system
+24 | ||     }
+25 | || }
    | ||_- in this macro invocation
 ...  |
    |
@@ -41,11 +42,12 @@ error[E0599]: the function or associated item `initialize_block` exists for stru
    |  __^
    | | _|
    | ||
-20 | ||     pub struct Runtime<Dummy>
-21 | ||     {
-22 | ||         System: frame_system
-23 | ||     }
-24 | || }
+20 | ||     type Migrations = (Dummy);
+21 | ||     pub struct Runtime
+22 | ||     {
+23 | ||         System: frame_system
+24 | ||     }
+25 | || }
    | ||_- in this macro invocation
 ...  |
    |
@@ -74,11 +76,12 @@ error[E0599]: the function or associated item `apply_extrinsic` exists for struc
    |  __^
    | | _|
    | ||
-20 | ||     pub struct Runtime<Dummy>
-21 | ||     {
-22 | ||         System: frame_system
-23 | ||     }
-24 | || }
+20 | ||     type Migrations = (Dummy);
+21 | ||     pub struct Runtime
+22 | ||     {
+23 | ||         System: frame_system
+24 | ||     }
+25 | || }
    | ||_- in this macro invocation
 ...  |
    |
@@ -107,11 +110,12 @@ error[E0599]: the function or associated item `finalize_block` exists for struct
    |  __^
    | | _|
    | ||
-20 | ||     pub struct Runtime<Dummy>
-21 | ||     {
-22 | ||         System: frame_system
-23 | ||     }
-24 | || }
+20 | ||     type Migrations = (Dummy);
+21 | ||     pub struct Runtime
+22 | ||     {
+23 | ||         System: frame_system
+24 | ||     }
+25 | || }
    | ||_- in this macro invocation
 ...  |
    |
@@ -140,11 +144,12 @@ error[E0599]: the function or associated item `validate_transaction` exists for
    |  __^
    | | _|
    | ||
-20 | ||     pub struct Runtime<Dummy>
-21 | ||     {
-22 | ||         System: frame_system
-23 | ||     }
-24 | || }
+20 | ||     type Migrations = (Dummy);
+21 | ||     pub struct Runtime
+22 | ||     {
+23 | ||         System: frame_system
+24 | ||     }
+25 | || }
    | ||_- in this macro invocation
 ...  |
    |
@@ -173,11 +178,12 @@ error[E0599]: the function or associated item `offchain_worker` exists for struc
    |  __^
    | | _|
    | ||
-20 | ||     pub struct Runtime<Dummy>
-21 | ||     {
-22 | ||         System: frame_system
-23 | ||     }
-24 | || }
+20 | ||     type Migrations = (Dummy);
+21 | ||     pub struct Runtime
+22 | ||     {
+23 | ||         System: frame_system
+24 | ||     }
+25 | || }
    | ||_- in this macro invocation
 ...  |
    |