allow pallets to specify an auto_construct_runtime

bin/node/runtime/src/lib.rs

@@ -819,7 +819,7 @@ construct_runtime!(
 		TechnicalMembership: pallet_membership::<Instance1>::{Module, Call, Storage, Event<T>, Config<T>},
 		FinalityTracker: pallet_finality_tracker::{Module, Call, Inherent},
 		Grandpa: pallet_grandpa::{Module, Call, Storage, Config, Event},
-		Treasury: pallet_treasury::{Module, Call, Storage, Config, Event<T>},
+		Treasury: pallet_treasury::{auto},
 		Contracts: pallet_contracts::{Module, Call, Config, Storage, Event<T>},
 		Sudo: pallet_sudo::{Module, Call, Config<T>, Storage, Event<T>},
 		ImOnline: pallet_im_online::{Module, Call, Storage, Event<T>, ValidateUnsigned, Config<T>},

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

@@ -22,19 +22,62 @@ use frame_support_procedural_tools::{generate_crate_access, generate_hidden_incl
 use parse::{ModuleDeclaration, RuntimeDefinition, WhereSection};
 use proc_macro::TokenStream;
 use proc_macro2::TokenStream as TokenStream2;
-use quote::quote;
-use syn::{Ident, Result, TypePath};
+use quote::{quote, quote_spanned};
+use syn::{Ident, Result, TypePath, spanned::Spanned};
 
 /// The fixed name of the system module.
 const SYSTEM_MODULE_NAME: &str = "System";
 
 pub fn construct_runtime(input: TokenStream) -> TokenStream {
+	let input_clone = input.clone().into();
 	let definition = syn::parse_macro_input!(input as RuntimeDefinition);
+
+	if let Some(preprocess) = construct_runtime_preprocess(&definition, input_clone)
+		.unwrap_or_else(|e| Some(e.to_compile_error()))
+	{
+		return preprocess.into()
+	}
+
 	construct_runtime_parsed(definition)
 		.unwrap_or_else(|e| e.to_compile_error())
 		.into()
 }
 
+fn construct_runtime_preprocess(
+	definition: &RuntimeDefinition,
+	input_clone: TokenStream2,
+) -> Result<Option<TokenStream2>> {
+	let mut auto_modules = vec![];
+	for module in definition.modules.content.inner.iter() {
+		if module.module_parts.iter().any(|p| p.keyword.name() == "auto") {
+			if module.module_parts.len() != 1 {
+				return Err(syn::Error::new(
+					module.module_parts[0].keyword.span(),
+					"Module parts must either provide explicit parts or use `auto` keyword but
+					cannot combine."
+				))
+			}
+
+			auto_modules.push(module.module.clone());
+		}
+	}
+
+	if !auto_modules.is_empty() {
+		let mut expand = input_clone;
+
+		while let Some(module) = auto_modules.pop()  {
+			expand = quote_spanned!(module.span() => #module::auto_construct_runtime!{
+				construct_runtime! { #expand   }
+			}
+			)
+		}
+
+		Ok(Some(expand))
+	} else {
+		Ok(None)
+	}
+}
+
 fn construct_runtime_parsed(definition: RuntimeDefinition) -> Result<TokenStream2> {
 	let RuntimeDefinition {
 		name,

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

@@ -24,7 +24,7 @@ use syn::{
 	token, Error, Ident, Result, Token,
 };
 
-mod keyword {
+pub mod keyword {
 	syn::custom_keyword!(Block);
 	syn::custom_keyword!(NodeBlock);
 	syn::custom_keyword!(UncheckedExtrinsic);
@@ -36,6 +36,7 @@ mod keyword {
 	syn::custom_keyword!(Origin);
 	syn::custom_keyword!(Inherent);
 	syn::custom_keyword!(ValidateUnsigned);
+	syn::custom_keyword!(auto);
 }
 
 #[derive(Debug)]
@@ -231,6 +232,7 @@ pub enum ModulePartKeyword {
 	Origin(keyword::Origin),
 	Inherent(keyword::Inherent),
 	ValidateUnsigned(keyword::ValidateUnsigned),
+	Auto(keyword::auto),
 }
 
 impl Parse for ModulePartKeyword {
@@ -253,6 +255,8 @@ impl Parse for ModulePartKeyword {
 			Ok(Self::Inherent(input.parse()?))
 		} else if lookahead.peek(keyword::ValidateUnsigned) {
 			Ok(Self::ValidateUnsigned(input.parse()?))
+		} else if lookahead.peek(keyword::auto) {
+			Ok(Self::Auto(input.parse()?))
 		} else {
 			Err(lookahead.error())
 		}
@@ -261,7 +265,7 @@ impl Parse for ModulePartKeyword {
 
 impl ModulePartKeyword {
 	/// Returns the name of `Self`.
-	fn name(&self) -> &'static str {
+	pub fn name(&self) -> &'static str {
 		match self {
 			Self::Module(_) => "Module",
 			Self::Call(_) => "Call",
@@ -271,6 +275,7 @@ impl ModulePartKeyword {
 			Self::Origin(_) => "Origin",
 			Self::Inherent(_) => "Inherent",
 			Self::ValidateUnsigned(_) => "ValidateUnsigned",
+			Self::Auto(_) => "auto",
 		}
 	}
 
@@ -313,6 +318,7 @@ impl Spanned for ModulePartKeyword {
 			Self::Origin(inner) => inner.span(),
 			Self::Inherent(inner) => inner.span(),
 			Self::ValidateUnsigned(inner) => inner.span(),
+			Self::Auto(inner) => inner.span(),
 		}
 	}
 }

frame/support/procedural/src/lib.rs

@@ -23,6 +23,7 @@
 
 mod storage;
 mod construct_runtime;
+mod replace_auto_with;
 
 use proc_macro::TokenStream;
 
@@ -260,6 +261,8 @@ pub fn decl_storage(input: TokenStream) -> TokenStream {
 ///         // Module with instances
 ///         Test3_Instance1: test3::<Instance1>::{Module, Call, Storage, Event<T, I>, Config<T, I>, Origin<T, I>},
 ///         Test3_DefaultInstance: test3::{Module, Call, Storage, Event<T>, Config<T>, Origin<T>},
+///
+///         TestAuto: pallet_with_auto_construct_runtime::{auto},
 ///     }
 /// )
 /// ```
@@ -282,6 +285,9 @@ pub fn decl_storage(input: TokenStream) -> TokenStream {
 ///                             inherent.
 /// - `ValidateUnsigned`      - If the module validates unsigned extrinsics.
 ///
+/// alternatively if the pallet provide the auto_contruct_runtime macro, parts can be automatically
+/// filled using `auto` keyword.
+///
 /// # Note
 ///
 /// The population of the genesis storage depends on the order of modules. So, if one of your
@@ -291,3 +297,24 @@ pub fn decl_storage(input: TokenStream) -> TokenStream {
 pub fn construct_runtime(input: TokenStream) -> TokenStream {
 	construct_runtime::construct_runtime(input)
 }
+
+/// Macro than replace the first found `auto` ident with some specified content.
+///
+/// # Example:
+///
+/// ```nocompile
+/// replace_auto_with!(
+///     { something or else } // content inside braces can be anything.
+///     Some content with at some point { an ident named auto } other auto are ignored
+/// )
+/// ```
+///
+/// will generate:
+///
+/// ```nocompile
+///     Some content with at some point { an ident named something or else } other auto are ignored
+/// ```
+#[proc_macro]
+pub fn replace_auto_with(input: TokenStream) -> TokenStream {
+	replace_auto_with::replace_auto_with(input)
+}

frame/support/procedural/src/replace_auto_with.rs

@@ -0,0 +1,72 @@
+use proc_macro2::{TokenStream, TokenTree, Group};
+use syn::spanned::Spanned;
+use std::iter::once;
+
+pub fn replace_auto_with(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+	let def = syn::parse_macro_input!(input as ReplaceAutoWithDef);
+	let replace_in_span = def.replace_in.span();
+
+	match replace_in_stream(&mut Some(def.replace_with), def.replace_in) {
+		Ok(stream) => stream.into(),
+		Err(_) => {
+			syn::Error::new(replace_in_span, "cannot find `auto` ident in given token stream")
+				.to_compile_error().into()
+		},
+	}
+}
+struct ReplaceAutoWithDef {
+	replace_with: TokenStream,
+	replace_in: TokenStream,
+}
+
+impl syn::parse::Parse for ReplaceAutoWithDef {
+	fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
+		let replace_with;
+		let _replace_with_bracket: syn::token::Brace = syn::braced!(replace_with in input);
+		let replace_with: TokenStream = replace_with.parse()?;
+		Ok(Self {
+			replace_with,
+			replace_in: input.parse()?,
+		})
+	}
+}
+
+// Replace the first found `auto` ident by content of `with`. `with` must be some (Option is used
+// for internal simplification).
+fn replace_in_stream(
+	with: &mut Option<TokenStream>,
+	stream: TokenStream
+) -> Result<TokenStream, ()> {
+	assert!(with.is_some(), "`with` must be some, Option is used because `with` is used only once");
+
+	let mut stream = stream.into_iter();
+	let mut builded_replaced = TokenStream::new();
+
+	loop {
+		match stream.next() {
+			Some(TokenTree::Group(group)) => {
+				let stream = group.stream();
+				match replace_in_stream(with, stream) {
+					Ok(stream) => {
+						builded_replaced.extend(once(TokenTree::Group(Group::new(group.delimiter(), stream))));
+						break;
+					}
+					Err(_) => {
+						builded_replaced.extend(once(TokenTree::Group(group)));
+					}
+				}
+			}
+			Some(TokenTree::Ident(ident)) if ident == "auto" => {
+				builded_replaced.extend(once(with.take().expect("with is used to replace only once")));
+				break;
+			}
+			Some(other) => builded_replaced.extend(once(other)),
+			None => return Err(())
+		}
+	}
+
+	builded_replaced.extend(stream);
+
+	Ok(builded_replaced)
+}
+

frame/support/src/lib.rs

@@ -267,7 +267,7 @@ macro_rules! ord_parameter_types {
 }
 
 #[doc(inline)]
-pub use frame_support_procedural::{decl_storage, construct_runtime};
+pub use frame_support_procedural::{decl_storage, construct_runtime, replace_auto_with};
 
 /// Return Err of the expression: `return Err($expression);`.
 ///

frame/treasury/src/lib.rs

@@ -111,6 +111,16 @@ type BalanceOf<T> = <<T as Trait>::Currency as Currency<<T as frame_system::Trai
 type PositiveImbalanceOf<T> = <<T as Trait>::Currency as Currency<<T as frame_system::Trait>::AccountId>>::PositiveImbalance;
 type NegativeImbalanceOf<T> = <<T as Trait>::Currency as Currency<<T as frame_system::Trait>::AccountId>>::NegativeImbalance;
 
+#[macro_export]
+macro_rules! auto_construct_runtime {
+	( $( $t:tt )* ) => {
+		frame_support::replace_auto_with! {
+			{ Module, Call, Storage, Config, Event<T> }
+			$( $t )*
+		}
+	}
+}
+
 pub trait Trait: frame_system::Trait {
 	/// The treasury's module id, used for deriving its sovereign account ID.
 	type ModuleId: Get<ModuleId>;