Refactor. Remove signature topic macro in favor of local custom ink attr in the derive

Author: SkymanOne

README.md

@@ -230,6 +230,7 @@ In a module annotated with `#[ink::contract]` these attributes are available:
 | `#[ink(constructor)]` | Applicable to method. | Flags a method for the ink! storage struct as constructor making it available to the API for instantiating the contract. |
 | `#[ink(event)]` | On `struct` definitions. | Defines an ink! event. A contract can define multiple such ink! events. |
 | `#[ink(anonymous)]` | Applicable to ink! events. | Tells the ink! codegen to treat the ink! event as anonymous which omits the event signature as topic upon emitting. Very similar to anonymous events in Solidity. |
+| `#[ink(signature_topic = _)]` | Applicable to ink! events. | Specifies custom signature topic of the event that allows to use manually specify shared event definition. |
 | `#[ink(topic)]` | Applicable on ink! event field. | Tells the ink! codegen to provide a topic hash for the given field. Every ink! event can only have a limited number of such topic fields. Similar semantics as to indexed event arguments in Solidity. |
 | `#[ink(payable)]` | Applicable to ink! messages. | Allows receiving value as part of the call of the ink! message. ink! constructors are implicitly payable. |
 | `#[ink(selector = S:u32)]` | Applicable to ink! messages and ink! constructors. | Specifies a concrete dispatch selector for the flagged entity. This allows a contract author to precisely control the selectors of their APIs making it possible to rename their API without breakage. |

crates/env/src/event.rs

@@ -195,11 +195,19 @@ impl EventTopicsAmount for state::NoRemainingTopics {
 /// builder.
 ///
 /// Normally this trait should be implemented automatically via `#[derive(ink::Event)`.
-pub trait Event: scale::Encode + GetSignatureTopic {
+pub trait Event: scale::Encode {
     /// 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.
+    ///
+    /// It can be automatically calculated or manually specified.
+    ///
+    /// 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: core::option::Option<[u8; 32]>;
+
     /// Guides event topic serialization using the given topics builder.
     fn topics<E, B>(
         &self,
@@ -209,16 +217,3 @@ pub trait Event: scale::Encode + GetSignatureTopic {
         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

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

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

@@ -15,7 +15,6 @@
 use crate::GenerateCode;
 use derive_more::From;
 use proc_macro2::TokenStream as TokenStream2;
-use quote::quote;
 use syn::spanned::Spanned;
 
 /// Generates code for the event item.
@@ -33,39 +32,20 @@ impl GenerateCode for Event<'_> {
             .item
             .anonymous()
             .then(|| quote::quote! { #[ink(anonymous)] });
-
-        let signature_topic = self.generate_signature_topic();
+        let signature_topic = self
+            .item
+            .signature_topic_hash()
+            .map(|hash| quote::quote! { #[ink(signature_topic = #hash)] });
         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
+            #signature_topic
             #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

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

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

@@ -62,10 +62,6 @@ 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/codegen/src/lib.rs

@@ -29,7 +29,10 @@ use crate::{
     utils::extract_cfg_attributes,
 };
 
-pub use signature_topic::SignatureTopic;
+pub use signature_topic::{
+    SignatureTopic,
+    SignatureTopicArg,
+};
 
 /// A checked ink! event with its configuration.
 #[derive(Debug, PartialEq, Eq)]

crates/ink/ir/src/ir/event/mod.rs

@@ -46,35 +46,43 @@ impl From<&[u8; 32]> for SignatureTopicArg {
     }
 }
 
-impl TryFrom<&ast::MetaValue> for SignatureTopicArg {
+impl TryFrom<&syn::Lit> for SignatureTopicArg {
     type Error = syn::Error;
 
-    fn try_from(value: &ast::MetaValue) -> Result<Self, Self::Error> {
-        if let ast::MetaValue::Lit(lit) = value {
-            if let syn::Lit::Str(s) = lit {
-                let bytes: [u8; 32] = serde_hex::from_hex(&s.value())
+    fn try_from(lit: &syn::Lit) -> Result<Self, Self::Error> {
+        if let syn::Lit::Str(s) = lit {
+            let bytes: [u8; 32] = serde_hex::from_hex(&s.value())
                     .map_err(|_| {
                         format_err_spanned!(
-                            value,
+                            lit,
                             "`signature_topic` has invalid hex string",
                         )
                     })?
                     .try_into()
                     .map_err(|e: Vec<u8>| {
                         format_err_spanned!(
-                            value,
+                            lit,
                             "`signature_topic` is expected to be 32-byte hash. Found {} bytes",
                             e.len()
                         )
                     })?;
 
-                Ok(Self { topic: bytes })
-            } else {
-                Err(format_err_spanned!(
-                    value,
-                    "Expected string literal argument for the `signature_topic`"
-                ))
-            }
+            Ok(Self { topic: bytes })
+        } else {
+            Err(format_err_spanned!(
+                lit,
+                "Expected string literal argument for the `signature_topic`"
+            ))
+        }
+    }
+}
+
+impl TryFrom<&ast::MetaValue> for SignatureTopicArg {
+    type Error = syn::Error;
+
+    fn try_from(value: &ast::MetaValue) -> Result<Self, Self::Error> {
+        if let ast::MetaValue::Lit(lit) = value {
+            Self::try_from(lit)
         } else {
             Err(format_err_spanned!(
                 value,
@@ -109,6 +117,22 @@ impl TryFrom<ast::AttributeArgs> for Option<SignatureTopicArg> {
     }
 }
 
+impl TryFrom<&syn::MetaNameValue> for SignatureTopicArg {
+    type Error = syn::Error;
+
+    fn try_from(nv: &syn::MetaNameValue) -> Result<Self, Self::Error> {
+        if nv.path.is_ident("signature_topic") {
+            if let syn::Expr::Lit(lit_expr) = &nv.value {
+                Self::try_from(&lit_expr.lit)
+            } else {
+                Err(format_err_spanned!(&nv.value, "Expected literal argument"))
+            }
+        } else {
+            Err(format_err_spanned!(nv, "Expected `signature_topic` ident"))
+        }
+    }
+}
+
 /// The signature topic argument of an event variant.
 ///
 /// Used as part of `ink::signature_topic` macro.

crates/ink/ir/src/ir/event/signature_topic.rs

@@ -73,6 +73,7 @@ pub use self::{
     event::{
         Event,
         SignatureTopic,
+        SignatureTopicArg,
     },
     ink_test::InkTest,
     item::{