Implement #[pallet::hold_reason]

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

@@ -0,0 +1,60 @@
+// This file is part of Substrate.
+
+// Copyright (C) Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License
+
+use crate::construct_runtime::{parse::PalletPath, Pallet};
+use proc_macro2::{Ident, TokenStream};
+use quote::quote;
+
+pub fn expand_outer_hold_reason(pallet_decls: &[Pallet]) -> TokenStream {
+	let mut conversion_fns = Vec::new();
+	let hold_reason_variants = pallet_decls.iter().filter_map(|decl| {
+		decl.find_part("HoldReason").map(|_| {
+			let variant_name = &decl.name;
+			let path = &decl.path;
+			let index = &decl.index;
+
+			conversion_fns.push(expand_conversion_fn(path, variant_name));
+
+			quote! {
+				#[codec(index = #index)]
+				#variant_name(#path::HoldReason),
+			}
+		})
+	});
+
+	quote! {
+		#[derive(
+			Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Encode, Decode, MaxEncodedLen, Debug,
+			TypeInfo,
+		)]
+		pub enum RuntimeHoldReason {
+			#( #hold_reason_variants )*
+		}
+
+		#( #conversion_fns )*
+	}
+}
+
+fn expand_conversion_fn(path: &PalletPath, variant_name: &Ident) -> TokenStream {
+	quote! {
+		impl From<#path::HoldReason> for RuntimeHoldReason {
+			fn from(hr: #path::HoldReason) -> Self {
+				RuntimeHoldReason::#variant_name
+			}
+		}
+	}
+}

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

@@ -18,6 +18,7 @@
 mod call;
 mod config;
 mod event;
+mod hold_reason;
 mod inherent;
 mod metadata;
 mod origin;
@@ -26,6 +27,7 @@ mod unsigned;
 pub use call::expand_outer_dispatch;
 pub use config::expand_outer_config;
 pub use event::expand_outer_event;
+pub use hold_reason::expand_outer_hold_reason;
 pub use inherent::expand_outer_inherent;
 pub use metadata::expand_runtime_metadata;
 pub use origin::expand_outer_origin;

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

@@ -265,6 +265,7 @@ fn construct_runtime_final_expansion(
 	let inherent =
 		expand::expand_outer_inherent(&name, &block, &unchecked_extrinsic, &pallets, &scrate);
 	let validate_unsigned = expand::expand_outer_validate_unsigned(&name, &pallets, &scrate);
+	let hold_reason = expand::expand_outer_hold_reason(&pallets);
 	let integrity_test = decl_integrity_test(&scrate);
 	let static_assertions = decl_static_assertions(&name, &pallets, &scrate);
 
@@ -307,6 +308,8 @@ fn construct_runtime_final_expansion(
 
 		#validate_unsigned
 
+		#hold_reason
+
 		#integrity_test
 
 		#static_assertions

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

@@ -38,6 +38,7 @@ mod keyword {
 	syn::custom_keyword!(Origin);
 	syn::custom_keyword!(Inherent);
 	syn::custom_keyword!(ValidateUnsigned);
+	syn::custom_keyword!(HoldReason);
 	syn::custom_keyword!(exclude_parts);
 	syn::custom_keyword!(use_parts);
 }
@@ -370,6 +371,7 @@ pub enum PalletPartKeyword {
 	Origin(keyword::Origin),
 	Inherent(keyword::Inherent),
 	ValidateUnsigned(keyword::ValidateUnsigned),
+	HoldReason(keyword::HoldReason),
 }
 
 impl Parse for PalletPartKeyword {
@@ -392,6 +394,8 @@ impl Parse for PalletPartKeyword {
 			Ok(Self::Inherent(input.parse()?))
 		} else if lookahead.peek(keyword::ValidateUnsigned) {
 			Ok(Self::ValidateUnsigned(input.parse()?))
+		} else if lookahead.peek(keyword::HoldReason) {
+			Ok(Self::HoldReason(input.parse()?))
 		} else {
 			Err(lookahead.error())
 		}
@@ -410,6 +414,7 @@ impl PalletPartKeyword {
 			Self::Origin(_) => "Origin",
 			Self::Inherent(_) => "Inherent",
 			Self::ValidateUnsigned(_) => "ValidateUnsigned",
+			Self::HoldReason(_) => "HoldReason",
 		}
 	}
 
@@ -435,6 +440,7 @@ impl Spanned for PalletPartKeyword {
 			Self::Origin(inner) => inner.span(),
 			Self::Inherent(inner) => inner.span(),
 			Self::ValidateUnsigned(inner) => inner.span(),
+			Self::HoldReason(inner) => inner.span(),
 		}
 	}
 }

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

@@ -104,7 +104,7 @@ impl EventDef {
 		let item = if let syn::Item::Enum(item) = item {
 			item
 		} else {
-			return Err(syn::Error::new(item.span(), "Invalid pallet::event, expected item enum"))
+			return Err(syn::Error::new(item.span(), "Invalid pallet::event, expected enum item"))
 		};
 
 		let event_attrs: Vec<PalletEventDepositAttr> =

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

@@ -0,0 +1,83 @@
+// This file is part of Substrate.
+
+// Copyright (C) Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use quote::ToTokens;
+use syn::spanned::Spanned;
+
+mod keyword {
+	syn::custom_keyword!(HoldReason);
+}
+
+pub struct HoldReasonDef {
+	/// The index of the HoldReason item in the pallet module.
+	pub index: usize,
+	/// The HoldReason keyword used (contains span).
+	pub hold_reason: keyword::HoldReason,
+	/// The span of the pallet::hold_reason attribute.
+	pub attr_span: proc_macro2::Span,
+}
+
+impl HoldReasonDef {
+	pub fn try_from(
+		attr_span: proc_macro2::Span,
+		index: usize,
+		item: &mut syn::Item,
+	) -> syn::Result<Self> {
+		let item = if let syn::Item::Enum(item) = item {
+			item
+		} else {
+			return Err(syn::Error::new(
+				item.span(),
+				"Invalid pallet::hold_reason, expected enum item",
+			))
+		};
+
+		if !matches!(item.vis, syn::Visibility::Public(_)) {
+			let msg = "Invalid pallet::hold_reason, `HoldReason` must be public";
+			return Err(syn::Error::new(item.span(), msg))
+		}
+
+		let has_derive_attr = item
+			.attrs
+			.iter()
+			.find(|attr| {
+				attr.parse_meta()
+					.ok()
+					.map(|meta| match meta {
+						syn::Meta::List(syn::MetaList { path, .. }) =>
+							path.get_ident().map(|ident| ident == "derive").unwrap_or(false),
+						_ => false,
+					})
+					.unwrap_or(false)
+			})
+			.is_some();
+
+		if !has_derive_attr {
+			let derive_attr: syn::Attribute = syn::parse_quote! {
+				#[derive(
+					Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Encode, Decode, MaxEncodedLen,
+					Debug, TypeInfo,
+				)]
+			};
+			item.attrs.push(derive_attr);
+		}
+
+		let hold_reason = syn::parse2::<keyword::HoldReason>(item.ident.to_token_stream())?;
+
+		Ok(HoldReasonDef { index, hold_reason, attr_span })
+	}
+}

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

@@ -27,6 +27,7 @@ pub mod extra_constants;
 pub mod genesis_build;
 pub mod genesis_config;
 pub mod helper;
+pub mod hold_reason;
 pub mod hooks;
 pub mod inherent;
 pub mod origin;
@@ -56,6 +57,7 @@ pub struct Def {
 	pub genesis_build: Option<genesis_build::GenesisBuildDef>,
 	pub validate_unsigned: Option<validate_unsigned::ValidateUnsignedDef>,
 	pub extra_constants: Option<extra_constants::ExtraConstantsDef>,
+	pub hold_reason: Option<hold_reason::HoldReasonDef>,
 	pub type_values: Vec<type_value::TypeValueDef>,
 	pub frame_system: syn::Ident,
 	pub frame_support: syn::Ident,
@@ -89,6 +91,7 @@ impl Def {
 		let mut genesis_build = None;
 		let mut validate_unsigned = None;
 		let mut extra_constants = None;
+		let mut hold_reason = None;
 		let mut storages = vec![];
 		let mut type_values = vec![];
 
@@ -135,6 +138,8 @@ impl Def {
 				Some(PalletAttr::ExtraConstants(_)) =>
 					extra_constants =
 						Some(extra_constants::ExtraConstantsDef::try_from(index, item)?),
+				Some(PalletAttr::HoldReason(span)) =>
+					hold_reason = Some(hold_reason::HoldReasonDef::try_from(span, index, item)?),
 				Some(attr) => {
 					let msg = "Invalid duplicated attribute";
 					return Err(syn::Error::new(attr.span(), msg))
@@ -171,6 +176,7 @@ impl Def {
 			origin,
 			inherent,
 			storages,
+			hold_reason,
 			type_values,
 			frame_system,
 			frame_support,
@@ -385,6 +391,7 @@ mod keyword {
 	syn::custom_keyword!(generate_store);
 	syn::custom_keyword!(Store);
 	syn::custom_keyword!(extra_constants);
+	syn::custom_keyword!(hold_reason);
 }
 
 /// Parse attributes for item in pallet module
@@ -404,6 +411,7 @@ enum PalletAttr {
 	ValidateUnsigned(proc_macro2::Span),
 	TypeValue(proc_macro2::Span),
 	ExtraConstants(proc_macro2::Span),
+	HoldReason(proc_macro2::Span),
 }
 
 impl PalletAttr {
@@ -423,6 +431,7 @@ impl PalletAttr {
 			Self::ValidateUnsigned(span) => *span,
 			Self::TypeValue(span) => *span,
 			Self::ExtraConstants(span) => *span,
+			Self::HoldReason(span) => *span,
 		}
 	}
 }
@@ -464,6 +473,8 @@ impl syn::parse::Parse for PalletAttr {
 			Ok(PalletAttr::TypeValue(content.parse::<keyword::type_value>()?.span()))
 		} else if lookahead.peek(keyword::extra_constants) {
 			Ok(PalletAttr::ExtraConstants(content.parse::<keyword::extra_constants>()?.span()))
+		} else if lookahead.peek(keyword::hold_reason) {
+			Ok(PalletAttr::HoldReason(content.parse::<keyword::hold_reason>()?.span()))
 		} else {
 			Err(lookahead.error())
 		}

frame/support/test/tests/pallet.rs

@@ -476,6 +476,11 @@ pub mod pallet {
 		}
 	}
 
+	#[pallet::hold_reason]
+	pub enum HoldReason {
+		Staking,
+	}
+
 	#[derive(codec::Encode, sp_runtime::RuntimeDebug)]
 	#[cfg_attr(feature = "std", derive(codec::Decode))]
 	pub enum InherentError {

frame/support/test/tests/pallet_ui/hold_reason_non_enum.rs

@@ -0,0 +1,14 @@
+#[frame_support::pallet]
+mod pallet {
+	#[pallet::config]
+	pub trait Config: frame_system::Config {}
+
+	#[pallet::pallet]
+	pub struct Pallet<T>(core::marker::PhantomData<T>);
+
+	#[pallet::hold_reason]
+	pub struct HoldReason;
+}
+
+fn main() {
+}

frame/support/test/tests/pallet_ui/hold_reason_non_enum.stderr

@@ -0,0 +1,5 @@
+error: Invalid pallet::hold_reason, expected enum item
+  --> tests/pallet_ui/hold_reason_non_enum.rs:10:2
+   |
+10 |     pub struct HoldReason;
+   |     ^^^

frame/support/test/tests/pallet_ui/hold_reason_not_pub.rs

@@ -0,0 +1,14 @@
+#[frame_support::pallet]
+mod pallet {
+	#[pallet::config]
+	pub trait Config: frame_system::Config {}
+
+	#[pallet::pallet]
+	pub struct Pallet<T>(core::marker::PhantomData<T>);
+
+	#[pallet::hold_reason]
+    enum HoldReason {}
+}
+
+fn main() {
+}

frame/support/test/tests/pallet_ui/hold_reason_not_pub.stderr

@@ -0,0 +1,5 @@
+error: Invalid pallet::hold_reason, `HoldReason` must be public
+  --> tests/pallet_ui/hold_reason_not_pub.rs:10:5
+   |
+10 |     enum HoldReason {}
+   |     ^^^^