feat(abigen): use structs for outputs (#664)

* feat(abigen): use structs for outputs

* update CHANGELOG

* make clippy happy

* fix lints

CHANGELOG.md

@@ -94,6 +94,8 @@
 
 ### Unreleased
 
+- Substitute output tuples with rust struct types for function calls
+  [#664](https://github.com/gakonst/ethers-rs/pull/664)
 - Add AbiType implementation during EthAbiType expansion
   [#647](https://github.com/gakonst/ethers-rs/pull/647)
 - fix Etherscan conditional HTTP support

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

@@ -38,8 +38,7 @@ impl Context {
         let sorted_events: BTreeMap<_, _> = self.abi.events.iter().collect();
         let filter_methods = sorted_events
             .values()
-            .map(std::ops::Deref::deref)
-            .flatten()
+            .flat_map(std::ops::Deref::deref)
             .map(|event| self.expand_filter(event))
             .collect::<Vec<_>>();
 

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

@@ -28,8 +28,7 @@ impl Context {
         let sorted_functions: BTreeMap<_, _> = self.abi.functions.iter().collect();
         let functions = sorted_functions
             .values()
-            .map(std::ops::Deref::deref)
-            .flatten()
+            .flat_map(std::ops::Deref::deref)
             .map(|function| {
                 let signature = function.abi_signature();
                 self.expand_function(function, aliases.get(&signature).cloned())
@@ -50,7 +49,7 @@ impl Context {
         alias: Option<&MethodAlias>,
     ) -> Result<TokenStream> {
         let call_name = expand_call_struct_name(function, alias);
-        let fields = self.expand_input_pairs(function)?;
+        let fields = self.expand_input_params(function)?;
         // expand as a tuple if all fields are anonymous
         let all_anonymous_fields = function.inputs.iter().all(|input| input.name.is_empty());
         let call_type_definition = if all_anonymous_fields {
@@ -163,16 +162,34 @@ impl Context {
     }
 
     /// Expands to the `name : type` pairs of the function's inputs
-    fn expand_input_pairs(&self, fun: &Function) -> Result<Vec<(TokenStream, TokenStream)>> {
+    fn expand_input_params(&self, fun: &Function) -> Result<Vec<(TokenStream, TokenStream)>> {
         let mut args = Vec::with_capacity(fun.inputs.len());
         for (idx, param) in fun.inputs.iter().enumerate() {
             let name = util::expand_input_name(idx, &param.name);
-            let ty = self.expand_input_param(fun, &param.name, &param.kind)?;
+            let ty = self.expand_input_param_type(fun, &param.name, &param.kind)?;
             args.push((name, ty));
         }
         Ok(args)
     }
 
+    /// Expands to the return type of a function
+    fn expand_outputs(&self, fun: &Function) -> Result<TokenStream> {
+        let mut outputs = Vec::with_capacity(fun.outputs.len());
+        for param in fun.outputs.iter() {
+            let ty = self.expand_output_param_type(fun, param, &param.kind)?;
+            outputs.push(ty);
+        }
+
+        let return_ty = match outputs.len() {
+            0 => quote! { () },
+            1 => outputs[0].clone(),
+            _ => {
+                quote! { (#( #outputs ),*) }
+            }
+        };
+        Ok(return_ty)
+    }
+
     /// Expands the arguments for the call that eventually calls the contract
     fn expand_contract_call_args(&self, fun: &Function) -> Result<TokenStream> {
         let mut call_args = Vec::with_capacity(fun.inputs.len());
@@ -202,7 +219,8 @@ impl Context {
         Ok(call_args)
     }
 
-    fn expand_input_param(
+    /// returns the Tokenstream for the corresponding rust type of the param
+    fn expand_input_param_type(
         &self,
         fun: &Function,
         param: &str,
@@ -210,13 +228,13 @@ impl Context {
     ) -> Result<TokenStream> {
         match kind {
             ParamType::Array(ty) => {
-                let ty = self.expand_input_param(fun, param, ty)?;
+                let ty = self.expand_input_param_type(fun, param, ty)?;
                 Ok(quote! {
                     ::std::vec::Vec<#ty>
                 })
             }
             ParamType::FixedArray(ty, size) => {
-                let ty = self.expand_input_param(fun, param, ty)?;
+                let ty = self.expand_input_param_type(fun, param, ty)?;
                 let size = *size;
                 Ok(quote! {[#ty; #size]})
             }
@@ -235,27 +253,61 @@ impl Context {
         }
     }
 
+    /// returns the Tokenstream for the corresponding rust type of the output param
+    fn expand_output_param_type(
+        &self,
+        fun: &Function,
+        param: &Param,
+        kind: &ParamType,
+    ) -> Result<TokenStream> {
+        match kind {
+            ParamType::Array(ty) => {
+                let ty = self.expand_output_param_type(fun, param, ty)?;
+                Ok(quote! {
+                    ::std::vec::Vec<#ty>
+                })
+            }
+            ParamType::FixedArray(ty, size) => {
+                let ty = self.expand_output_param_type(fun, param, ty)?;
+                let size = *size;
+                Ok(quote! {[#ty; #size]})
+            }
+            ParamType::Tuple(_) => {
+                let ty = if let Some(rust_struct_name) =
+                    param.internal_type.as_ref().and_then(|s| {
+                        self.internal_structs.get_function_output_struct_type(&fun.name, s)
+                    }) {
+                    let ident = util::ident(rust_struct_name);
+                    quote! {#ident}
+                } else {
+                    types::expand(kind)?
+                };
+                Ok(ty)
+            }
+            _ => types::expand(kind),
+        }
+    }
+
     /// Expands a single function with the given alias
     fn expand_function(
         &self,
         function: &Function,
         alias: Option<MethodAlias>,
     ) -> Result<TokenStream> {
+        let ethers_contract = ethers_contract_crate();
+
         let name = expand_function_name(function, alias.as_ref());
         let selector = expand_selector(function.selector());
 
-        // TODO use structs
-        let outputs = expand_fn_outputs(&function.outputs)?;
-
-        let ethers_contract = ethers_contract_crate();
-
-        let result = quote! { #ethers_contract::builders::ContractCall<M, #outputs> };
-
         let contract_args = self.expand_contract_call_args(function)?;
         let function_params =
-            self.expand_input_pairs(function)?.into_iter().map(|(name, ty)| quote! { #name: #ty });
+            self.expand_input_params(function)?.into_iter().map(|(name, ty)| quote! { #name: #ty });
         let function_params = quote! { #( , #function_params )* };
 
+        let outputs = self.expand_outputs(function)?;
+
+        let result = quote! { #ethers_contract::builders::ContractCall<M, #outputs> };
+
         let doc = util::expand_doc(&format!(
             "Calls the contract's `{}` (0x{}) function",
             function.name,
@@ -478,20 +530,6 @@ impl Context {
     }
 }
 
-fn expand_fn_outputs(outputs: &[Param]) -> Result<TokenStream> {
-    match outputs.len() {
-        0 => Ok(quote! { () }),
-        1 => types::expand(&outputs[0].kind),
-        _ => {
-            let types = outputs
-                .iter()
-                .map(|param| types::expand(&param.kind))
-                .collect::<Result<Vec<_>>>()?;
-            Ok(quote! { (#( #types ),*) })
-        }
-    }
-}
-
 fn expand_selector(selector: Selector) -> TokenStream {
     let bytes = selector.iter().copied().map(Literal::u8_unsuffixed);
     quote! { [#( #bytes ),*] }
@@ -575,6 +613,20 @@ mod tests {
 
     use super::*;
 
+    fn expand_fn_outputs(outputs: &[Param]) -> Result<TokenStream> {
+        match outputs.len() {
+            0 => Ok(quote! { () }),
+            1 => types::expand(&outputs[0].kind),
+            _ => {
+                let types = outputs
+                    .iter()
+                    .map(|param| types::expand(&param.kind))
+                    .collect::<Result<Vec<_>>>()?;
+                Ok(quote! { (#( #types ),*) })
+            }
+        }
+    }
+
     // packs the argument in a tuple to be used for the contract call
     fn expand_inputs_call_arg(inputs: &[Param]) -> TokenStream {
         let names = inputs

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

@@ -312,6 +312,22 @@ impl InternalStructs {
             .map(String::as_str)
     }
 
+    /// Returns the name of the rust type that will be generated if the given output is a struct
+    /// NOTE: this does not account for arrays or fixed arrays
+    pub fn get_function_output_struct_type(
+        &self,
+        function: &str,
+        internal_type: &str,
+    ) -> Option<&str> {
+        self.outputs
+            .get(function)
+            .and_then(|outputs| {
+                outputs.iter().find(|s| s.as_str() == struct_type_identifier(internal_type))
+            })
+            .and_then(|id| self.rust_type_names.get(id))
+            .map(String::as_str)
+    }
+
     /// Returns the mapping table of abi `internal type identifier -> rust type`
     pub fn rust_type_names(&self) -> &HashMap<String, String> {
         &self.rust_type_names

ethers-contract/src/multicall/mod.rs

@@ -191,7 +191,7 @@ impl<M: Middleware> Multicall<M> {
     /// If more than the maximum number of supported calls are added. The maximum
     /// limits is constrained due to tokenization/detokenization support for tuples
     pub fn add_call<D: Detokenize>(&mut self, call: ContractCall<M, D>) -> &mut Self {
-        assert!(!(self.calls.len() >= 16), "Cannot support more than {} calls", 16);
+        assert!(self.calls.len() < 16, "Cannot support more than {} calls", 16);
 
         match (call.tx.to(), call.tx.data()) {
             (Some(NameOrAddress::Address(target)), Some(data)) => {

ethers-contract/tests/abigen.rs

@@ -419,3 +419,32 @@ fn can_handle_case_sensitive_calls() {
     let _ = contract.index();
     let _ = contract.INDEX();
 }
+
+#[tokio::test]
+async fn can_abiencoderv2_output() {
+    abigen!(AbiEncoderv2Test, "ethers-contract/tests/solidity-contracts/abiencoderv2test_abi.json",);
+    let ganache = ethers_core::utils::Ganache::new().spawn();
+    let from = ganache.addresses()[0];
+    let provider = Provider::try_from(ganache.endpoint())
+        .unwrap()
+        .with_sender(from)
+        .interval(std::time::Duration::from_millis(10));
+    let client = Arc::new(provider);
+
+    let contract = "AbiencoderV2Test";
+    let path = "./tests/solidity-contracts/Abiencoderv2Test.sol";
+    let compiled = Solc::default().compile_source(path).unwrap();
+    let compiled = compiled.get(path, contract).unwrap();
+    let factory = ethers_contract::ContractFactory::new(
+        compiled.abi.unwrap().clone(),
+        compiled.bytecode().unwrap().clone(),
+        client.clone(),
+    );
+    let addr = factory.deploy(()).unwrap().legacy().send().await.unwrap().address();
+
+    let contract = AbiEncoderv2Test::new(addr, client.clone());
+    let person = Person { name: "Alice".to_string(), age: 20u64.into() };
+
+    let res = contract.default_person().call().await.unwrap();
+    assert_eq!(res, person);
+}

ethers-contract/tests/solidity-contracts/Abiencoderv2Test.sol

@@ -0,0 +1,12 @@
+pragma solidity >=0.6.0;
+pragma experimental ABIEncoderV2;
+
+contract AbiencoderV2Test {
+    struct Person {
+        string name;
+        uint age;
+    }
+    function defaultPerson() public pure returns (Person memory) {
+        return Person("Alice", 20);
+    }
+}

ethers-contract/tests/solidity-contracts/abiencoderv2test_abi.json

@@ -0,0 +1 @@
+[{"inputs":[],"name":"defaultPerson","outputs":[{"components":[{"internalType":"string","name":"name","type":"string"},{"internalType":"uint256","name":"age","type":"uint256"}],"internalType":"struct Hello.Person","name":"","type":"tuple"}],"stateMutability":"pure","type":"function"}]

ethers-etherscan/src/gas.rs

@@ -123,7 +123,7 @@ mod tests {
             assert!(oracle.fast_gas_price > 0);
             assert!(oracle.last_block > 0);
             assert!(oracle.suggested_base_fee > 0.0);
-            assert!(oracle.gas_used_ratio.len() > 0);
+            assert!(!oracle.gas_used_ratio.is_empty());
         })
         .await
     }

ethers-signers/src/ledger/app.rs

@@ -206,7 +206,7 @@ impl LedgerEthereum {
         let mut bytes = vec![depth as u8];
         for derivation_index in elements {
             let hardened = derivation_index.contains('\'');
-            let mut index = derivation_index.replace("'", "").parse::<u32>().unwrap();
+            let mut index = derivation_index.replace('\'', "").parse::<u32>().unwrap();
             if hardened {
                 index |= 0x80000000;
             }

ethers-solc/src/compile.rs

@@ -202,7 +202,7 @@ impl Solc {
     pub fn version_req(source: &Source) -> Result<VersionReq> {
         let version = utils::find_version_pragma(&source.content)
             .ok_or(SolcError::PragmaNotFound)?
-            .replace(" ", ",");
+            .replace(' ', ",");
 
         // Somehow, Solidity semver without an operator is considered to be "exact",
         // but lack of operator automatically marks the operator as Caret, so we need