Custom signature topic

CHANGELOG.md

@@ -6,6 +6,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+- Custom signature topic in Events - #[2031](https://github.com/paritytech/ink/pull/2031)
+
 
 ## Version 5.0.0-rc
 

Cargo.toml

@@ -80,6 +80,7 @@ wasm-instrument = { version = "0.4.0" }
 which = { version = "5.0.0" }
 xxhash-rust = { version = "0.8" }
 const_env = { version = "0.1"}
+hex = { version = "0.4" }
 
 # Substrate dependencies
 pallet-contracts-primitives = { version = "26.0.0", default-features = false }

crates/env/src/event.rs

@@ -195,17 +195,11 @@ impl EventTopicsAmount for state::NoRemainingTopics {
 /// builder.
 ///
 /// Normally this trait should be implemented automatically via `#[derive(ink::Event)`.
-pub trait Event: scale::Encode {
+pub trait Event: scale::Encode + GetSignatureTopic {
     /// Type state indicating how many event topics are to be expected by the topics
     /// builder.
     type RemainingTopics: EventTopicsAmount;
 
-    /// The unique signature topic of the event. `None` for anonymous events.
-    ///
-    /// Usually this is calculated using the `#[derive(ink::Event)]` derive, which by
-    /// default calculates this as `blake2b("Event(field1_type,field2_type)")`
-    const SIGNATURE_TOPIC: Option<[u8; 32]>;
-
     /// Guides event topic serialization using the given topics builder.
     fn topics<E, B>(
         &self,
@@ -215,3 +209,16 @@ pub trait Event: scale::Encode {
         E: Environment,
         B: TopicsBuilderBackend<E>;
 }
+
+/// Getter that returns the signature topic for the specific event.
+///
+/// It can be automatically calculated or manually specified.
+///
+/// The unique signature topic of the event. `None` for anonymous events.
+///
+/// Usually this is calculated using the `#[derive(ink::Event)]` derive, which by
+/// default calculates this as `blake2b("Event(field1_type,field2_type)")`
+pub trait GetSignatureTopic {
+    /// Retrieve the signature topic
+    const SIGNATURE_TOPIC: core::option::Option<[u8; 32]>;
+}

crates/env/src/lib.rs

@@ -120,7 +120,10 @@ pub use self::{
         Error,
         Result,
     },
-    event::Event,
+    event::{
+        Event,
+        GetSignatureTopic,
+    },
     types::{
         AccountIdGuard,
         DefaultEnvironment,

crates/ink/codegen/Cargo.toml

@@ -30,6 +30,7 @@ blake2 = { workspace = true }
 heck = { workspace = true }
 scale = { workspace = true }
 impl-serde = { workspace = true, default-features = true }
+hex = { workspace = true }
 
 serde = { workspace = true, features = ["derive"] }
 serde_json = { workspace = true }

crates/ink/codegen/src/generator/as_dependency/contract_ref.rs

@@ -81,8 +81,8 @@ impl ContractRef<'_> {
             .storage()
             .attrs()
             .iter()
-            .cloned()
-            .filter(syn::Attribute::is_doc_attribute);
+            .filter(|&x| syn::Attribute::is_doc_attribute(x))
+            .cloned();
         let storage_ident = self.contract.module().storage().ident();
         let ref_ident = self.generate_contract_ref_ident();
         quote_spanned!(span=>

crates/ink/codegen/src/generator/event.rs

@@ -15,28 +15,57 @@
 use crate::GenerateCode;
 use derive_more::From;
 use proc_macro2::TokenStream as TokenStream2;
+use quote::quote;
+use syn::spanned::Spanned;
 
-/// Generates code for the storage item.
+/// Generates code for the event item.
 #[derive(From, Copy, Clone)]
 pub struct Event<'a> {
     /// The storage item to generate code for.
     item: &'a ir::Event,
 }
 
 impl GenerateCode for Event<'_> {
-    /// Generates ink! storage item code.
+    /// Generates ink! event item code.
     fn generate_code(&self) -> TokenStream2 {
         let item = self.item.item();
         let anonymous = self
             .item
             .anonymous()
             .then(|| quote::quote! { #[ink(anonymous)] });
+
+        let signature_topic = self.generate_signature_topic();
+        let cfg_attrs = self.item.get_cfg_attrs(item.span());
+
         quote::quote! (
+            #( #cfg_attrs )*
             #[cfg_attr(feature = "std", derive(::ink::EventMetadata))]
             #[derive(::ink::Event)]
             #[::ink::scale_derive(Encode, Decode)]
+            #signature_topic
             #anonymous
             #item
         )
     }
 }
+
+impl Event<'_> {
+    /// Generates the `#[ink::signature_topic]` attribute for the given event.
+    ///
+    /// # Note
+    /// If `anonymous` is present, no attribute is generated
+    /// and the blank implementation is generated by `#derive(Event)`.
+    fn generate_signature_topic(&self) -> TokenStream2 {
+        let signature_topic = if let Some(hash) = self.item.signature_topic_hash() {
+            quote! {
+                #[::ink::signature_topic(hash = #hash)]
+            }
+        } else if self.item.anonymous() {
+            quote! {}
+        } else {
+            quote! { #[::ink::signature_topic] }
+        };
+
+        quote! { #signature_topic }
+    }
+}

crates/ink/codegen/src/generator/mod.rs

@@ -38,6 +38,7 @@ mod ink_test;
 mod item_impls;
 mod metadata;
 mod selector;
+mod signature_topic;
 mod storage;
 mod storage_item;
 mod trait_def;
@@ -67,6 +68,7 @@ pub use self::{
         SelectorBytes,
         SelectorId,
     },
+    signature_topic::SignatureTopic,
     storage::Storage,
     storage_item::StorageItem,
     trait_def::TraitDefinition,

crates/ink/codegen/src/generator/signature_topic.rs

@@ -0,0 +1,79 @@
+// Copyright (C) Parity Technologies (UK) Ltd.
+//
+// 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::GenerateCode;
+use derive_more::From;
+use ir::HexLiteral;
+use proc_macro2::TokenStream as TokenStream2;
+use quote::quote;
+use syn::spanned::Spanned;
+
+/// Generates code to generate signature topic.
+#[derive(From, Copy, Clone)]
+pub struct SignatureTopic<'a> {
+    /// The event item to generate code for.
+    item: &'a ir::SignatureTopic,
+}
+
+impl GenerateCode for SignatureTopic<'_> {
+    /// Generates ink! signature topic item code.
+    fn generate_code(&self) -> TokenStream2 {
+        let item = self.item.item();
+        let signature_topic = self.generate_signature_topic();
+        let cfg_attrs = self.item.get_cfg_attrs(item.span());
+
+        quote::quote! (
+            #( #cfg_attrs )*
+            #signature_topic
+            #item
+        )
+    }
+}
+
+impl SignatureTopic<'_> {
+    /// Generates the implementation of `GetSignatureTopic` trait.
+    fn generate_signature_topic(&self) -> TokenStream2 {
+        let item_ident = &self.item.item().ident;
+        let signature_topic = if let Some(bytes) = self.item.signature_topic() {
+            let hash_bytes = bytes.map(|b| b.hex_padded_suffixed());
+            quote! { ::core::option::Option::Some([ #( #hash_bytes ),* ]) }
+        } else {
+            let calculated_topic = signature_topic(&self.item.item().fields, item_ident);
+            quote! { ::core::option::Option::Some(#calculated_topic) }
+        };
+
+        quote! {
+            impl ::ink::env::GetSignatureTopic for #item_ident {
+                const SIGNATURE_TOPIC: ::core::option::Option<[u8; 32]> = #signature_topic;
+            }
+        }
+    }
+}
+
+/// The signature topic of an event variant.
+///
+/// Calculated with `blake2b("Event(field1_type,field2_type)")`.
+fn signature_topic(fields: &syn::Fields, event_ident: &syn::Ident) -> TokenStream2 {
+    let fields = fields
+        .iter()
+        .map(|field| {
+            quote::ToTokens::to_token_stream(&field.ty)
+                .to_string()
+                .replace(' ', "")
+        })
+        .collect::<Vec<_>>()
+        .join(",");
+    let topic_str = format!("{}({fields})", event_ident);
+    quote!(::ink::blake2x256!(#topic_str))
+}

crates/ink/codegen/src/lib.rs

@@ -62,6 +62,10 @@ impl<'a> CodeGenerator for &'a ir::Event {
     type Generator = generator::Event<'a>;
 }
 
+impl<'a> CodeGenerator for &'a ir::SignatureTopic {
+    type Generator = generator::SignatureTopic<'a>;
+}
+
 impl<'a> CodeGenerator for &'a ir::StorageItem {
     type Generator = generator::StorageItem<'a>;
 }

crates/ink/ir/Cargo.toml

@@ -24,6 +24,8 @@ proc-macro2 = { workspace = true }
 itertools = { workspace = true }
 either = { workspace = true }
 blake2 = { workspace = true }
+hex = { workspace = true }
+
 ink_prelude = { workspace = true }
 
 [features]