test: payable vs non-payable

libevm/precompilegen/Test.sol

@@ -24,13 +24,17 @@ interface IPrecompile {
     function Pure() external pure returns (bool canReadState, bool canWriteState);
 
     function NeitherViewNorPure() external returns (bool canReadState, bool canWriteState);
+
+    function Payable() external payable returns (uint256 value);
+
+    function NonPayable() external;
 }
 
 /// @dev Testing contract to exercise the implementaiton of `IPrecompile`.
 contract PrecompileTest {
     IPrecompile immutable precompile;
 
-    constructor(IPrecompile _precompile) {
+    constructor(IPrecompile _precompile) payable {
         precompile = _precompile;
     }
 
@@ -107,4 +111,15 @@ contract PrecompileTest {
         assertReadOnly(IPrecompile.NeitherViewNorPure.selector, true, true);
         emit Called("NeitherViewNorPure()");
     }
+
+    function Transfer() external {
+        uint256 value = precompile.Payable{value: 42}();
+        assert(value == 42);
+
+        (bool ok,) = address(precompile).call{value: 42}(abi.encodeWithSelector(IPrecompile.NonPayable.selector));
+        assert(!ok);
+        // TODO: DO NOT MERGE without checking the return data
+
+        emit Called("Transfer()");
+    }
 }

libevm/precompilegen/main_test.go

@@ -89,12 +89,15 @@ func TestGeneratedPrecompile(t *testing.T) {
 	txOpts, err := bind.NewKeyedTransactorWithChainID(key, big.NewInt(1337))
 	require.NoError(t, err, "bind.NewKeyedTransactorWithChainID(..., 1337)")
 	txOpts.GasLimit = 30e6
+	txOpts.Value = big.NewInt(1e9)
 
 	client := sim.Client()
 	_, tx, test, err := DeployPrecompileTest(txOpts, client, precompile)
 	require.NoError(t, err, "DeployPrecompileTest(...)")
 	sim.Commit()
 	successfulTxReceipt(ctx, t, client, tx)
+
+	txOpts.Value = nil
 	suite := &PrecompileTestSession{
 		Contract:     test,
 		TransactOpts: *txOpts,
@@ -166,6 +169,12 @@ func TestGeneratedPrecompile(t *testing.T) {
 			},
 			wantCalledEvent: "NeitherViewNorPure()",
 		},
+		{
+			transact: func() (*types.Transaction, error) {
+				return suite.Transfer()
+			},
+			wantCalledEvent: "Transfer()",
+		},
 	}
 
 	for _, tt := range tests {
@@ -248,3 +257,11 @@ func (contract) Pure(env vm.PrecompileEnvironment) (bool, bool, error) {
 func (contract) NeitherViewNorPure(env vm.PrecompileEnvironment) (bool, bool, error) {
 	return canReadState(env), canWriteState(env), nil
 }
+
+func (contract) Payable(env vm.PrecompileEnvironment) (*big.Int, error) {
+	return env.Value().ToBig(), nil
+}
+
+func (contract) NonPayable(env vm.PrecompileEnvironment) error {
+	return nil
+}

libevm/precompilegen/precompile.go.tmpl

@@ -102,17 +102,19 @@ type dispatch struct{}
 
 {{range methods .ABI}}
 func (dispatch) {{.Name}}(impl Contract, env vm.PrecompileEnvironment, input []byte) ([]byte, error) {
+    {{if or (gt (len .Inputs) 0) (gt (len .Outputs) 0) -}}
     method := methods[{{hex .ID}}]
+    {{- end}}
 
-    {{if gt (len .Inputs) 0}}
+    {{if gt (len .Inputs) 0 -}}
     inputs, err := method.Inputs.Unpack(input[abi.SelectorByteLen:])
     if err != nil {
         return nil, err
     }
     {{- range $i, $in := .Inputs}}
     i{{$i}} := inputs[{{$i}}].({{type $in}})
     {{- end}}
-    {{end}}
+    {{- end}}
 
     {
     {{args "o" (len .Outputs) false true}} := impl.{{.Name}}({{args "i" (len .Inputs) true false}})
@@ -123,7 +125,7 @@ func (dispatch) {{.Name}}(impl Contract, env vm.PrecompileEnvironment, input []b
     return method.Outputs.Pack({{args "o" (len .Outputs) false false}})
     {{- else -}}
     return nil, nil
-    {{end}}
+    {{- end}}
     }
 }
 {{end}}