fix: Fixed contract_source_metadata compilation issue when multiple…

… impl blocks are there (#1118)

near-sdk-macros/src/core_impl/code_generator/metadata.rs

@@ -0,0 +1,17 @@
+use proc_macro2::Ident;
+use quote::quote;
+use syn::Generics;
+
+/// Generates a view method to retrieve the source metadata.
+pub(crate) fn generate_contract_metadata_method(
+    ident: &Ident,
+    generics: &Generics,
+) -> proc_macro2::TokenStream {
+    quote! {
+        impl #generics #ident #generics {
+            pub fn contract_source_metadata() {
+                near_sdk::env::value_return(CONTRACT_SOURCE_METADATA.as_bytes())
+            }
+        }
+    }
+}

near-sdk-macros/src/core_impl/code_generator/mod.rs

@@ -11,5 +11,6 @@ mod item_impl_info;
 pub use item_impl_info::*;
 
 pub(crate) mod ext;
+pub(crate) mod metadata;
 
 pub(crate) mod serializer;

near-sdk-macros/src/lib.rs

@@ -3,11 +3,12 @@ extern crate proc_macro;
 
 mod core_impl;
 
-use core_impl::ext::generate_ext_structs;
+use core_impl::{ext::generate_ext_structs, metadata::generate_contract_metadata_method};
+
 use proc_macro::TokenStream;
 
 use self::core_impl::*;
-use proc_macro2::Span;
+use proc_macro2::{Ident, Span};
 use quote::{quote, ToTokens};
 use syn::{parse_quote, ImplItem, ItemEnum, ItemImpl, ItemStruct, ItemTrait, WhereClause};
 
@@ -114,8 +115,25 @@ pub fn near_bindgen(attr: TokenStream, item: TokenStream) -> TokenStream {
         return core_impl::near_events(attr, item);
     }
 
+    let generate_metadata = |ident: &Ident,
+                             generics: &syn::Generics|
+     -> Result<proc_macro2::TokenStream, proc_macro2::TokenStream> {
+        let metadata_impl_gen = generate_contract_metadata_method(ident, generics).into();
+        let metadata_impl_gen = syn::parse::<ItemImpl>(metadata_impl_gen)
+            .expect("failed to generate contract metadata");
+        process_impl_block(metadata_impl_gen)
+    };
+
     if let Ok(input) = syn::parse::<ItemStruct>(item.clone()) {
         let metadata = core_impl::contract_source_metadata_const(attr);
+
+        let metadata_impl_gen = generate_metadata(&input.ident, &input.generics);
+
+        let metadata_impl_gen = match metadata_impl_gen {
+            Ok(metadata) => metadata,
+            Err(err) => return err.into(),
+        };
+
         let ext_gen = generate_ext_structs(&input.ident, Some(&input.generics));
         #[cfg(feature = "__abi-embed-checked")]
         let abi_embedded = abi::embed();
@@ -126,9 +144,17 @@ pub fn near_bindgen(attr: TokenStream, item: TokenStream) -> TokenStream {
             #ext_gen
             #abi_embedded
             #metadata
+            #metadata_impl_gen
         })
     } else if let Ok(input) = syn::parse::<ItemEnum>(item.clone()) {
         let metadata = core_impl::contract_source_metadata_const(attr);
+        let metadata_impl_gen = generate_metadata(&input.ident, &input.generics);
+
+        let metadata_impl_gen = match metadata_impl_gen {
+            Ok(metadata) => metadata,
+            Err(err) => return err.into(),
+        };
+
         let ext_gen = generate_ext_structs(&input.ident, Some(&input.generics));
         #[cfg(feature = "__abi-embed-checked")]
         let abi_embedded = abi::embed();
@@ -139,8 +165,9 @@ pub fn near_bindgen(attr: TokenStream, item: TokenStream) -> TokenStream {
             #ext_gen
             #abi_embedded
             #metadata
+            #metadata_impl_gen
         })
-    } else if let Ok(mut input) = syn::parse::<ItemImpl>(item) {
+    } else if let Ok(input) = syn::parse::<ItemImpl>(item) {
         for method in &input.items {
             if let ImplItem::Fn(m) = method {
                 let ident = &m.sig.ident;
@@ -155,46 +182,11 @@ pub fn near_bindgen(attr: TokenStream, item: TokenStream) -> TokenStream {
                 }
             }
         }
-
-        if input.trait_.is_none() {
-            let contract_source_metadata = quote! {
-                pub fn contract_source_metadata() {
-                    near_sdk::env::value_return(CONTRACT_SOURCE_METADATA.as_bytes())
-                }
-            };
-
-            match syn::parse2::<ImplItem>(contract_source_metadata) {
-                Ok(x) => {
-                    input.items.push(x);
-                }
-                Err(err) => {
-                    return err.to_compile_error().into();
-                }
-            }
+        match process_impl_block(input) {
+            Ok(output) => output,
+            Err(output) => output,
         }
-
-        let item_impl_info = match ItemImplInfo::new(&mut input) {
-            Ok(x) => x,
-            Err(err) => {
-                return err.to_compile_error().into();
-            }
-        };
-
-        #[cfg(not(feature = "__abi-generate"))]
-        let abi_generated = quote! {};
-        #[cfg(feature = "__abi-generate")]
-        let abi_generated = abi::generate(&item_impl_info);
-
-        let generated_code = item_impl_info.wrapper_code();
-
-        // Add wrapper methods for ext call API
-        let ext_generated_code = item_impl_info.generate_ext_wrapper_code();
-        TokenStream::from(quote! {
-            #ext_generated_code
-            #input
-            #generated_code
-            #abi_generated
-        })
+        .into()
     } else {
         TokenStream::from(
             syn::Error::new(
@@ -206,6 +198,39 @@ pub fn near_bindgen(attr: TokenStream, item: TokenStream) -> TokenStream {
     }
 }
 
+// This function deals with impl block processing, generating wrappers and ABI.
+//
+// # Arguments
+// * input - impl block to process.
+//
+// The Result has a TokenStream error type, because those need to be propagated to the compiler.
+fn process_impl_block(
+    mut input: ItemImpl,
+) -> Result<proc_macro2::TokenStream, proc_macro2::TokenStream> {
+    let item_impl_info = match ItemImplInfo::new(&mut input) {
+        Ok(x) => x,
+        Err(err) => return Err(err.to_compile_error()),
+    };
+
+    #[cfg(not(feature = "__abi-generate"))]
+    let abi_generated = quote! {};
+    #[cfg(feature = "__abi-generate")]
+    let abi_generated = abi::generate(&item_impl_info);
+
+    let generated_code = item_impl_info.wrapper_code();
+
+    // Add wrapper methods for ext call API
+    let ext_generated_code = item_impl_info.generate_ext_wrapper_code();
+
+    Ok(TokenStream::from(quote! {
+        #ext_generated_code
+        #input
+        #generated_code
+        #abi_generated
+    })
+    .into())
+}
+
 /// `ext_contract` takes a Rust Trait and converts it to a module with static methods.
 /// Each of these static methods takes positional arguments defined by the Trait,
 /// then the receiver_id, the attached deposit and the amount of gas and returns a new Promise.

near-sdk/compilation_tests/all.rs

@@ -35,4 +35,5 @@ fn compilation_tests() {
     t.pass("compilation_tests/handle_result_alias.rs");
     t.pass("compilation_tests/contract_metadata.rs");
     t.compile_fail("compilation_tests/contract_metadata_fn_name.rs");
+    t.pass("compilation_tests/contract_metadata_bindgen.rs");
 }

near-sdk/compilation_tests/contract_metadata_bindgen.rs

@@ -0,0 +1,20 @@
+use near_account_id::AccountIdRef;
+use near_sdk::near_bindgen;
+
+#[near_bindgen]
+struct Contract {}
+
+#[near_bindgen]
+impl Contract {
+    pub fn anything() {}
+}
+
+#[near_bindgen]
+impl Contract {
+    pub fn anything_else() {}
+}
+
+fn main() {
+    let ext = Contract::ext(AccountIdRef::new_or_panic("0000").into());
+    ext.contract_source_metadata();
+}

near-sdk/compilation_tests/impl_generic.rs

@@ -2,6 +2,7 @@
 
 use borsh::{BorshDeserialize, BorshSerialize};
 use near_sdk::near_bindgen;
+#[allow(unused_imports)]
 use std::marker::PhantomData;
 
 #[near_bindgen]

near-sdk/compilation_tests/impl_generic.stderr

@@ -1,5 +1,11 @@
 error: Impl type parameters are not supported for smart contracts.
-  --> $DIR/impl_generic.rs:15:6
+  --> compilation_tests/impl_generic.rs:10:20
    |
-15 | impl<'a, T: 'a + std::fmt::Display> Incrementer<T> {
+10 | struct Incrementer<T> {
+   |                    ^
+
+error: Impl type parameters are not supported for smart contracts.
+  --> compilation_tests/impl_generic.rs:16:6
+   |
+16 | impl<'a, T: 'a + std::fmt::Display> Incrementer<T> {
    |      ^^