accounts/abi: generate TryPack* methods for abigen v2 bindings (#31692)

1. Fix the error return format.
**todo**: ~~`bindtype` needs more complex logic to fix it.~~
`
if err != nil {
  return nil, err
}
if err == nil {
  return obj, nil
}
`
2. ~~Return pointer type object to avoid copying the whole struct
content.~~
3. Give the panic decision to the user.
4. Fix empty line at the end of function.

**TODO**: ~~fix some related test cases.~~

---------

Co-authored-by: Jared Wasinger <j-wasinger@hotmail.com>

Author: mask-pp

accounts/abi/abigen/bindv2_test.go

@@ -281,7 +281,7 @@ func TestBindingV2ConvertedV1Tests(t *testing.T) {
 			}
 			// Set this environment variable to regenerate the test outputs.
 			if os.Getenv("WRITE_TEST_FILES") != "" {
-				if err := os.WriteFile((fname), []byte(have), 0666); err != nil {
+				if err := os.WriteFile(fname, []byte(have), 0666); err != nil {
 					t.Fatalf("err writing expected output to file: %v\n", err)
 				}
 			}

accounts/abi/abigen/source2.go.tpl

@@ -90,7 +90,8 @@ var (
 
 	{{range .Calls}}
 		// Pack{{.Normalized.Name}} is the Go binding used to pack the parameters required for calling
-		// the contract method with ID 0x{{printf "%x" .Original.ID}}.
+		// the contract method with ID 0x{{printf "%x" .Original.ID}}.  This method will panic if any
+		// invalid/nil inputs are passed.
 		//
 		// Solidity: {{.Original.String}}
 		func ({{ decapitalise $contract.Type}} *{{$contract.Type}}) Pack{{.Normalized.Name}}({{range .Normalized.Inputs}} {{.Name}} {{bindtype .Type $structs}}, {{end}}) []byte {
@@ -101,6 +102,15 @@ var (
 			return enc
 		}
 
+		// TryPack{{.Normalized.Name}} is the Go binding used to pack the parameters required for calling
+		// the contract method with ID 0x{{printf "%x" .Original.ID}}.  This method will return an error
+		// if any inputs are invalid/nil.
+		//
+		// Solidity: {{.Original.String}}
+		func ({{ decapitalise $contract.Type}} *{{$contract.Type}}) TryPack{{.Normalized.Name}}({{range .Normalized.Inputs}} {{.Name}} {{bindtype .Type $structs}}, {{end}}) ([]byte, error) {
+			return {{ decapitalise $contract.Type}}.abi.Pack("{{.Original.Name}}" {{range .Normalized.Inputs}}, {{.Name}}{{end}})
+		}
+
 		{{/* Unpack method is needed only when there are return args */}}
 		{{if .Normalized.Outputs }}
 			{{ if .Structured }}
@@ -133,8 +143,7 @@ var (
 					outstruct.{{capitalise .Name}} = *abi.ConvertType(out[{{$i}}], new({{bindtype .Type $structs}})).(*{{bindtype .Type $structs}})
 				{{- end }}
 				{{- end }}
-				return *outstruct, err
-				{{else}}
+				return *outstruct, nil{{else}}
 				if err != nil {
 					return {{range $i, $_ := .Normalized.Outputs}}{{if ispointertype .Type}}new({{underlyingbindtype .Type }}), {{else}}*new({{bindtype .Type $structs}}), {{end}}{{end}} err
 				}
@@ -145,8 +154,8 @@ var (
 				out{{$i}} := *abi.ConvertType(out[{{$i}}], new({{bindtype .Type $structs}})).(*{{bindtype .Type $structs}})
 				{{- end }}
 				{{- end}}
-				return {{range $i, $t := .Normalized.Outputs}}out{{$i}}, {{end}} err
-                {{- end}}
+				return {{range $i, $t := .Normalized.Outputs}}out{{$i}}, {{end}} nil
+				{{- end}}
 			}
 		{{end}}
 	{{end}}

accounts/abi/abigen/testdata/v2/callbackparam.go.txt

@@ -52,7 +52,8 @@ func (c *CallbackParam) Instance(backend bind.ContractBackend, addr common.Addre
 }
 
 // PackTest is the Go binding used to pack the parameters required for calling
-// the contract method with ID 0xd7a5aba2.
+// the contract method with ID 0xd7a5aba2.  This method will panic if any
+// invalid/nil inputs are passed.
 //
 // Solidity: function test(function callback) returns()
 func (callbackParam *CallbackParam) PackTest(callback [24]byte) []byte {
@@ -62,3 +63,12 @@ func (callbackParam *CallbackParam) PackTest(callback [24]byte) []byte {
 	}
 	return enc
 }
+
+// TryPackTest is the Go binding used to pack the parameters required for calling
+// the contract method with ID 0xd7a5aba2.  This method will return an error
+// if any inputs are invalid/nil.
+//
+// Solidity: function test(function callback) returns()
+func (callbackParam *CallbackParam) TryPackTest(callback [24]byte) ([]byte, error) {
+	return callbackParam.abi.Pack("test", callback)
+}

accounts/abi/abigen/testdata/v2/crowdsale.go.txt

@@ -64,7 +64,8 @@ func (crowdsale *Crowdsale) PackConstructor(ifSuccessfulSendTo common.Address, f
 }
 
 // PackAmountRaised is the Go binding used to pack the parameters required for calling
-// the contract method with ID 0x7b3e5e7b.
+// the contract method with ID 0x7b3e5e7b.  This method will panic if any
+// invalid/nil inputs are passed.
 //
 // Solidity: function amountRaised() returns(uint256)
 func (crowdsale *Crowdsale) PackAmountRaised() []byte {
@@ -75,6 +76,15 @@ func (crowdsale *Crowdsale) PackAmountRaised() []byte {
 	return enc
 }
 
+// TryPackAmountRaised is the Go binding used to pack the parameters required for calling
+// the contract method with ID 0x7b3e5e7b.  This method will return an error
+// if any inputs are invalid/nil.
+//
+// Solidity: function amountRaised() returns(uint256)
+func (crowdsale *Crowdsale) TryPackAmountRaised() ([]byte, error) {
+	return crowdsale.abi.Pack("amountRaised")
+}
+
 // UnpackAmountRaised is the Go binding that unpacks the parameters returned
 // from invoking the contract method with ID 0x7b3e5e7b.
 //
@@ -85,11 +95,12 @@ func (crowdsale *Crowdsale) UnpackAmountRaised(data []byte) (*big.Int, error) {
 		return new(big.Int), err
 	}
 	out0 := abi.ConvertType(out[0], new(big.Int)).(*big.Int)
-	return out0, err
+	return out0, nil
 }
 
 // PackBeneficiary is the Go binding used to pack the parameters required for calling
-// the contract method with ID 0x38af3eed.
+// the contract method with ID 0x38af3eed.  This method will panic if any
+// invalid/nil inputs are passed.
 //
 // Solidity: function beneficiary() returns(address)
 func (crowdsale *Crowdsale) PackBeneficiary() []byte {
@@ -100,6 +111,15 @@ func (crowdsale *Crowdsale) PackBeneficiary() []byte {
 	return enc
 }
 
+// TryPackBeneficiary is the Go binding used to pack the parameters required for calling
+// the contract method with ID 0x38af3eed.  This method will return an error
+// if any inputs are invalid/nil.
+//
+// Solidity: function beneficiary() returns(address)
+func (crowdsale *Crowdsale) TryPackBeneficiary() ([]byte, error) {
+	return crowdsale.abi.Pack("beneficiary")
+}
+
 // UnpackBeneficiary is the Go binding that unpacks the parameters returned
 // from invoking the contract method with ID 0x38af3eed.
 //
@@ -110,11 +130,12 @@ func (crowdsale *Crowdsale) UnpackBeneficiary(data []byte) (common.Address, erro
 		return *new(common.Address), err
 	}
 	out0 := *abi.ConvertType(out[0], new(common.Address)).(*common.Address)
-	return out0, err
+	return out0, nil
 }
 
 // PackCheckGoalReached is the Go binding used to pack the parameters required for calling
-// the contract method with ID 0x01cb3b20.
+// the contract method with ID 0x01cb3b20.  This method will panic if any
+// invalid/nil inputs are passed.
 //
 // Solidity: function checkGoalReached() returns()
 func (crowdsale *Crowdsale) PackCheckGoalReached() []byte {
@@ -125,8 +146,18 @@ func (crowdsale *Crowdsale) PackCheckGoalReached() []byte {
 	return enc
 }
 
+// TryPackCheckGoalReached is the Go binding used to pack the parameters required for calling
+// the contract method with ID 0x01cb3b20.  This method will return an error
+// if any inputs are invalid/nil.
+//
+// Solidity: function checkGoalReached() returns()
+func (crowdsale *Crowdsale) TryPackCheckGoalReached() ([]byte, error) {
+	return crowdsale.abi.Pack("checkGoalReached")
+}
+
 // PackDeadline is the Go binding used to pack the parameters required for calling
-// the contract method with ID 0x29dcb0cf.
+// the contract method with ID 0x29dcb0cf.  This method will panic if any
+// invalid/nil inputs are passed.
 //
 // Solidity: function deadline() returns(uint256)
 func (crowdsale *Crowdsale) PackDeadline() []byte {
@@ -137,6 +168,15 @@ func (crowdsale *Crowdsale) PackDeadline() []byte {
 	return enc
 }
 
+// TryPackDeadline is the Go binding used to pack the parameters required for calling
+// the contract method with ID 0x29dcb0cf.  This method will return an error
+// if any inputs are invalid/nil.
+//
+// Solidity: function deadline() returns(uint256)
+func (crowdsale *Crowdsale) TryPackDeadline() ([]byte, error) {
+	return crowdsale.abi.Pack("deadline")
+}
+
 // UnpackDeadline is the Go binding that unpacks the parameters returned
 // from invoking the contract method with ID 0x29dcb0cf.
 //
@@ -147,11 +187,12 @@ func (crowdsale *Crowdsale) UnpackDeadline(data []byte) (*big.Int, error) {
 		return new(big.Int), err
 	}
 	out0 := abi.ConvertType(out[0], new(big.Int)).(*big.Int)
-	return out0, err
+	return out0, nil
 }
 
 // PackFunders is the Go binding used to pack the parameters required for calling
-// the contract method with ID 0xdc0d3dff.
+// the contract method with ID 0xdc0d3dff.  This method will panic if any
+// invalid/nil inputs are passed.
 //
 // Solidity: function funders(uint256 ) returns(address addr, uint256 amount)
 func (crowdsale *Crowdsale) PackFunders(arg0 *big.Int) []byte {
@@ -162,6 +203,15 @@ func (crowdsale *Crowdsale) PackFunders(arg0 *big.Int) []byte {
 	return enc
 }
 
+// TryPackFunders is the Go binding used to pack the parameters required for calling
+// the contract method with ID 0xdc0d3dff.  This method will return an error
+// if any inputs are invalid/nil.
+//
+// Solidity: function funders(uint256 ) returns(address addr, uint256 amount)
+func (crowdsale *Crowdsale) TryPackFunders(arg0 *big.Int) ([]byte, error) {
+	return crowdsale.abi.Pack("funders", arg0)
+}
+
 // FundersOutput serves as a container for the return parameters of contract
 // method Funders.
 type FundersOutput struct {
@@ -181,12 +231,12 @@ func (crowdsale *Crowdsale) UnpackFunders(data []byte) (FundersOutput, error) {
 	}
 	outstruct.Addr = *abi.ConvertType(out[0], new(common.Address)).(*common.Address)
 	outstruct.Amount = abi.ConvertType(out[1], new(big.Int)).(*big.Int)
-	return *outstruct, err
-
+	return *outstruct, nil
 }
 
 // PackFundingGoal is the Go binding used to pack the parameters required for calling
-// the contract method with ID 0x7a3a0e84.
+// the contract method with ID 0x7a3a0e84.  This method will panic if any
+// invalid/nil inputs are passed.
 //
 // Solidity: function fundingGoal() returns(uint256)
 func (crowdsale *Crowdsale) PackFundingGoal() []byte {
@@ -197,6 +247,15 @@ func (crowdsale *Crowdsale) PackFundingGoal() []byte {
 	return enc
 }
 
+// TryPackFundingGoal is the Go binding used to pack the parameters required for calling
+// the contract method with ID 0x7a3a0e84.  This method will return an error
+// if any inputs are invalid/nil.
+//
+// Solidity: function fundingGoal() returns(uint256)
+func (crowdsale *Crowdsale) TryPackFundingGoal() ([]byte, error) {
+	return crowdsale.abi.Pack("fundingGoal")
+}
+
 // UnpackFundingGoal is the Go binding that unpacks the parameters returned
 // from invoking the contract method with ID 0x7a3a0e84.
 //
@@ -207,11 +266,12 @@ func (crowdsale *Crowdsale) UnpackFundingGoal(data []byte) (*big.Int, error) {
 		return new(big.Int), err
 	}
 	out0 := abi.ConvertType(out[0], new(big.Int)).(*big.Int)
-	return out0, err
+	return out0, nil
 }
 
 // PackPrice is the Go binding used to pack the parameters required for calling
-// the contract method with ID 0xa035b1fe.
+// the contract method with ID 0xa035b1fe.  This method will panic if any
+// invalid/nil inputs are passed.
 //
 // Solidity: function price() returns(uint256)
 func (crowdsale *Crowdsale) PackPrice() []byte {
@@ -222,6 +282,15 @@ func (crowdsale *Crowdsale) PackPrice() []byte {
 	return enc
 }
 
+// TryPackPrice is the Go binding used to pack the parameters required for calling
+// the contract method with ID 0xa035b1fe.  This method will return an error
+// if any inputs are invalid/nil.
+//
+// Solidity: function price() returns(uint256)
+func (crowdsale *Crowdsale) TryPackPrice() ([]byte, error) {
+	return crowdsale.abi.Pack("price")
+}
+
 // UnpackPrice is the Go binding that unpacks the parameters returned
 // from invoking the contract method with ID 0xa035b1fe.
 //
@@ -232,11 +301,12 @@ func (crowdsale *Crowdsale) UnpackPrice(data []byte) (*big.Int, error) {
 		return new(big.Int), err
 	}
 	out0 := abi.ConvertType(out[0], new(big.Int)).(*big.Int)
-	return out0, err
+	return out0, nil
 }
 
 // PackTokenReward is the Go binding used to pack the parameters required for calling
-// the contract method with ID 0x6e66f6e9.
+// the contract method with ID 0x6e66f6e9.  This method will panic if any
+// invalid/nil inputs are passed.
 //
 // Solidity: function tokenReward() returns(address)
 func (crowdsale *Crowdsale) PackTokenReward() []byte {
@@ -247,6 +317,15 @@ func (crowdsale *Crowdsale) PackTokenReward() []byte {
 	return enc
 }
 
+// TryPackTokenReward is the Go binding used to pack the parameters required for calling
+// the contract method with ID 0x6e66f6e9.  This method will return an error
+// if any inputs are invalid/nil.
+//
+// Solidity: function tokenReward() returns(address)
+func (crowdsale *Crowdsale) TryPackTokenReward() ([]byte, error) {
+	return crowdsale.abi.Pack("tokenReward")
+}
+
 // UnpackTokenReward is the Go binding that unpacks the parameters returned
 // from invoking the contract method with ID 0x6e66f6e9.
 //
@@ -257,7 +336,7 @@ func (crowdsale *Crowdsale) UnpackTokenReward(data []byte) (common.Address, erro
 		return *new(common.Address), err
 	}
 	out0 := *abi.ConvertType(out[0], new(common.Address)).(*common.Address)
-	return out0, err
+	return out0, nil
 }
 
 // CrowdsaleFundTransfer represents a FundTransfer event raised by the Crowdsale contract.