frame: GenesisBuild::build allowed in no_std

frame/elections-phragmen/src/lib.rs

@@ -743,7 +743,10 @@ pub mod pallet {
 					Members::<T>::mutate(|members| {
 						match members.binary_search_by(|m| m.who.cmp(member)) {
 							Ok(_) => {
-								panic!("Duplicate member in elections-phragmen genesis: {}", member)
+								panic!(
+									"Duplicate member in elections-phragmen genesis: {:?}",
+									member
+								)
 							},
 							Err(pos) => members.insert(
 								pos,

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

@@ -19,7 +19,6 @@ use crate::pallet::Def;
 
 ///
 /// * implement the trait `sp_runtime::BuildModuleGenesisStorage`
-/// * add #[cfg(feature = "std")] to GenesisBuild implementation.
 pub fn expand_genesis_build(def: &mut Def) -> proc_macro2::TokenStream {
 	let genesis_config = if let Some(genesis_config) = &def.genesis_config {
 		genesis_config
@@ -41,16 +40,6 @@ pub fn expand_genesis_build(def: &mut Def) -> proc_macro2::TokenStream {
 
 	let gen_cfg_use_gen = genesis_config.gen_kind.type_use_gen(genesis_build.attr_span);
 
-	let genesis_build_item =
-		&mut def.item.content.as_mut().expect("Checked by def parser").1[genesis_build.index];
-
-	let genesis_build_item_impl = if let syn::Item::Impl(impl_) = genesis_build_item {
-		impl_
-	} else {
-		unreachable!("Checked by genesis_build parser")
-	};
-
-	genesis_build_item_impl.attrs.push(syn::parse_quote!( #[cfg(feature = "std")] ));
 	let where_clause = &genesis_build.where_clause;
 
 	quote::quote_spanned!(genesis_build.attr_span =>

frame/support/src/lib.rs

@@ -1522,8 +1522,6 @@ pub mod tests {
 
 /// Prelude to be used alongside pallet macro, for ease of use.
 pub mod pallet_prelude {
-	#[cfg(feature = "std")]
-	pub use crate::traits::GenesisBuild;
 	pub use crate::{
 		dispatch::{
 			DispatchClass, DispatchError, DispatchResult, DispatchResultWithPostInfo, Parameter,
@@ -1540,8 +1538,8 @@ pub mod pallet_prelude {
 			},
 		},
 		traits::{
-			ConstU32, EnsureOrigin, Get, GetDefault, GetStorageVersion, Hooks, IsType,
-			PalletInfoAccess, StorageInfoTrait, StorageVersion, TypedGet,
+			ConstU32, EnsureOrigin, GenesisBuild, Get, GetDefault, GetStorageVersion, Hooks,
+			IsType, PalletInfoAccess, StorageInfoTrait, StorageVersion, TypedGet,
 		},
 		Blake2_128, Blake2_128Concat, Blake2_256, CloneNoBound, DebugNoBound, EqNoBound, Identity,
 		PartialEqNoBound, RuntimeDebug, RuntimeDebugNoBound, Twox128, Twox256, Twox64Concat,

frame/support/src/traits.rs

@@ -80,11 +80,9 @@ pub use metadata::{
 };
 
 mod hooks;
-#[cfg(feature = "std")]
-pub use hooks::GenesisBuild;
 pub use hooks::{
-	Hooks, IntegrityTest, OnFinalize, OnGenesis, OnIdle, OnInitialize, OnRuntimeUpgrade,
-	OnTimestampSet,
+	GenesisBuild, Hooks, IntegrityTest, OnFinalize, OnGenesis, OnIdle, OnInitialize,
+	OnRuntimeUpgrade, OnTimestampSet,
 };
 
 pub mod schedule;

frame/support/src/traits/hooks.rs

@@ -361,20 +361,21 @@ pub trait Hooks<BlockNumber> {
 
 /// A trait to define the build function of a genesis config, T and I are placeholder for pallet
 /// trait and pallet instance.
-#[cfg(feature = "std")]
 pub trait GenesisBuild<T, I = ()>: Default + sp_runtime::traits::MaybeSerializeDeserialize {
 	/// The build function is called within an externalities allowing storage APIs.
 	/// Thus one can write to storage using regular pallet storages.
 	fn build(&self);
 
 	/// Build the storage using `build` inside default storage.
+	#[cfg(feature = "std")]
 	fn build_storage(&self) -> Result<sp_runtime::Storage, String> {
 		let mut storage = Default::default();
 		self.assimilate_storage(&mut storage)?;
 		Ok(storage)
 	}
 
 	/// Assimilate the storage for this module into pre-existing overlays.
+	#[cfg(feature = "std")]
 	fn assimilate_storage(&self, storage: &mut sp_runtime::Storage) -> Result<(), String> {
 		sp_state_machine::BasicExternalities::execute_with_storage(storage, || {
 			self.build();

frame/support/test/Cargo.toml

@@ -36,21 +36,22 @@ test-pallet = { package = "frame-support-test-pallet", default-features = false,
 [features]
 default = ["std"]
 std = [
-	"serde/std",
 	"codec/std",
-	"scale-info/std",
 	"frame-benchmarking/std",
 	"frame-executive/std",
 	"frame-support/std",
 	"frame-system/std",
+	"scale-info/std",
+	"serde/std",
+	"sp-api/std",
+	"sp-arithmetic/std",
 	"sp-core/std",
-	"sp-std/std",
 	"sp-io/std",
 	"sp-runtime/std",
 	"sp-state-machine",
-	"sp-arithmetic/std",
+	"sp-std/std",
 	"sp-version/std",
-	"sp-api/std",
+	"test-pallet/std",
 ]
 try-runtime = [
 	"frame-support/try-runtime",

frame/support/test/pallet/Cargo.toml

@@ -14,6 +14,7 @@ targets = ["x86_64-unknown-linux-gnu"]
 [dependencies]
 codec = { package = "parity-scale-codec", version = "3.2.2", default-features = false, features = ["derive"] }
 scale-info = { version = "2.0.0", default-features = false, features = ["derive"] }
+serde = { version = "1.0.136", default-features = false, features = ["derive"] }
 frame-support = { version = "4.0.0-dev", default-features = false, path = "../../" }
 frame-system = { version = "4.0.0-dev", default-features = false, path = "../../../system" }
 
@@ -24,4 +25,5 @@ std = [
 	"frame-support/std",
 	"frame-system/std",
 	"scale-info/std",
+	"serde/std",
 ]

frame/system/src/lib.rs

@@ -707,7 +707,6 @@ pub struct EventRecord<E: Parameter + Member, T> {
 
 // Create a Hash with 69 for each byte,
 // only used to build genesis config.
-#[cfg(feature = "std")]
 fn hash69<T: AsMut<[u8]> + Default>() -> T {
 	let mut h = T::default();
 	h.as_mut().iter_mut().for_each(|byte| *byte = 69);

test-utils/runtime/src/substrate_test_pallet.rs

@@ -55,7 +55,7 @@ pub mod pallet {
 	pub type Authorities<T> = StorageValue<_, Vec<Public>, ValueQuery>;
 
 	#[pallet::genesis_config]
-	#[cfg_attr(feature = "std", derive(Default))]
+	#[derive(Default)]
 	pub struct GenesisConfig {
 		pub authorities: Vec<Public>,
 	}