Implement Multicall functionality for batched calls

.github/workflows/ci.yml

@@ -1,10 +1,12 @@
-on: push
+on: pull_request
 
 name: Tests
 
-# set for fetching ABIs for abigen from etherscan
+# Yeah I know it's bad practice to have API keys, this is a read-only API key
+# so that we do not get rate limited by Etherscan (and it's free to generate as
+# many as you want)
 env:
-  ETHERSCAN_API_KEY: ${{ secrets.ETHERSCAN_API_KEY }}
+  ETHERSCAN_API_KEY: 76XKCZ4QKZYTJS8PBFUDZ292JBKEKS4974
 
 jobs:
   tests:

ethers-contract/Cargo.toml

@@ -18,6 +18,7 @@ ethers-signers = { version = "0.1.3", path = "../ethers-signers" }
 ethers-core = { version = "0.1.3", path = "../ethers-core" }
 
 serde = { version = "1.0.110", default-features = false }
+serde_json = "1.0.55"
 rustc-hex = { version = "2.1.0", default-features = false }
 thiserror = { version = "1.0.15", default-features = false }
 once_cell = { version = "1.3.1", default-features = false }

ethers-contract/ethers-contract-abigen/src/contract/methods.rs

@@ -40,15 +40,7 @@ fn expand_function(function: &Function, alias: Option<Ident>) -> Result<TokenStr
 
     let outputs = expand_fn_outputs(&function.outputs)?;
 
-    let is_mutable = matches!(
-        function.state_mutability,
-        StateMutability::Nonpayable | StateMutability::Payable
-    );
-    let result = if !is_mutable {
-        quote! { ContractCall<P, S, #outputs> }
-    } else {
-        quote! { ContractCall<P, S, H256> }
-    };
+    let result = quote! { ContractCall<P, S, #outputs> };
 
     let arg = expand_inputs_call_arg(&function.inputs);
     let doc = util::expand_doc(&format!(
@@ -85,8 +77,13 @@ pub(crate) fn expand_inputs_call_arg(inputs: &[Param]) -> TokenStream {
     let names = inputs
         .iter()
         .enumerate()
-        .map(|(i, param)| util::expand_input_name(i, &param.name));
-    quote! { ( #( #names ,)* ) }
+        .map(|(i, param)| util::expand_input_name(i, &param.name))
+        .collect::<Vec<TokenStream>>();
+    match names.len() {
+        0 => quote! { () },
+        1 => quote! { #( #names )* },
+        _ => quote! { ( #(#names, )* ) },
+    }
 }
 
 fn expand_fn_outputs(outputs: &[Param]) -> Result<TokenStream> {
@@ -113,6 +110,54 @@ mod tests {
     use super::*;
     use ethers_core::abi::ParamType;
 
+    #[test]
+    fn test_expand_inputs_call_arg() {
+        // no inputs
+        let params = vec![];
+        let token_stream = expand_inputs_call_arg(&params);
+        assert_eq!(token_stream.to_string(), "( )");
+
+        // single input
+        let params = vec![Param {
+            name: "arg_a".to_string(),
+            kind: ParamType::Address,
+        }];
+        let token_stream = expand_inputs_call_arg(&params);
+        assert_eq!(token_stream.to_string(), "arg_a");
+
+        // two inputs
+        let params = vec![
+            Param {
+                name: "arg_a".to_string(),
+                kind: ParamType::Address,
+            },
+            Param {
+                name: "arg_b".to_string(),
+                kind: ParamType::Uint(256usize),
+            },
+        ];
+        let token_stream = expand_inputs_call_arg(&params);
+        assert_eq!(token_stream.to_string(), "( arg_a , arg_b , )");
+
+        // three inputs
+        let params = vec![
+            Param {
+                name: "arg_a".to_string(),
+                kind: ParamType::Address,
+            },
+            Param {
+                name: "arg_b".to_string(),
+                kind: ParamType::Uint(128usize),
+            },
+            Param {
+                name: "arg_c".to_string(),
+                kind: ParamType::Bool,
+            },
+        ];
+        let token_stream = expand_inputs_call_arg(&params);
+        assert_eq!(token_stream.to_string(), "( arg_a , arg_b , arg_c , )");
+    }
+
     #[test]
     fn expand_inputs_empty() {
         assert_quote!(expand_inputs(&[]).unwrap().to_string(), {},);
@@ -157,7 +202,7 @@ mod tests {
     }
 
     #[test]
-    fn expand_fn_outputs_muliple() {
+    fn expand_fn_outputs_multiple() {
         assert_quote!(
             expand_fn_outputs(&[
                 Param {

ethers-contract/src/lib.rs

@@ -24,6 +24,9 @@ pub use factory::ContractFactory;
 
 mod event;
 
+mod multicall;
+pub use multicall::Multicall;
+
 /// This module exposes low lever builder structures which are only consumed by the
 /// type-safe ABI bindings generators.
 pub mod builders {