manifest: add method validity check

Refs. #1699.

pkg/smartcontract/manifest/abi.go

@@ -54,6 +54,12 @@ func (a *ABI) IsValid() error {
 	if len(a.Methods) == 0 {
 		return errors.New("ABI contains no methods")
 	}
+	for i := range a.Methods {
+		err := a.Methods[i].IsValid()
+		if err != nil {
+			return err
+		}
+	}
 	for i := range a.Events {
 		err := a.Events[i].IsValid()
 		if err != nil {

pkg/smartcontract/manifest/event.go

@@ -2,7 +2,6 @@ package manifest
 
 import (
 	"errors"
-	"sort"
 
 	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
 )
@@ -18,22 +17,7 @@ func (e *Event) IsValid() error {
 	if e.Name == "" {
 		return errors.New("empty or absent name")
 	}
-	if len(e.Parameters) > 1 {
-		paramNames := make([]string, len(e.Parameters))
-		for i := range e.Parameters {
-			paramNames[i] = e.Parameters[i].Name
-		}
-		sort.Strings(paramNames)
-		for i := range paramNames {
-			if i == 0 {
-				continue
-			}
-			if paramNames[i] == paramNames[i-1] {
-				return errors.New("duplicate parameter name")
-			}
-		}
-	}
-	return nil
+	return Parameters(e.Parameters).AreValid()
 }
 
 // ToStackItem converts Event to stackitem.Item.

pkg/smartcontract/manifest/method.go

@@ -16,6 +16,21 @@ type Method struct {
 	Safe       bool                    `json:"safe"`
 }
 
+// IsValid checks Method consistency and correctness.
+func (m *Method) IsValid() error {
+	if m.Name == "" {
+		return errors.New("empty or absent name")
+	}
+	if m.Offset < 0 {
+		return errors.New("negative offset")
+	}
+	_, err := smartcontract.ConvertToParamType(int(m.ReturnType))
+	if err != nil {
+		return err
+	}
+	return Parameters(m.Parameters).AreValid()
+}
+
 // ToStackItem converts Method to stackitem.Item.
 func (m *Method) ToStackItem() stackitem.Item {
 	params := make([]stackitem.Item, len(m.Parameters))

pkg/smartcontract/manifest/method_test.go

@@ -10,6 +10,27 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func TestMethodIsValid(t *testing.T) {
+	m := &Method{}
+	require.Error(t, m.IsValid()) // No name.
+
+	m.Name = "qwerty"
+	require.NoError(t, m.IsValid())
+
+	m.Offset = -100
+	require.Error(t, m.IsValid())
+
+	m.Offset = 100
+	m.ReturnType = 0x42 // Invalid type.
+	require.Error(t, m.IsValid())
+
+	m.ReturnType = smartcontract.BoolType
+	require.NoError(t, m.IsValid())
+
+	m.Parameters = append(m.Parameters, NewParameter("param", smartcontract.BoolType), NewParameter("param", smartcontract.BoolType))
+	require.Error(t, m.IsValid())
+}
+
 func TestMethod_ToStackItemFromStackItem(t *testing.T) {
 	m := &Method{
 		Name:       "mur",

pkg/smartcontract/manifest/parameter.go

@@ -14,6 +14,9 @@ type Parameter struct {
 	Type smartcontract.ParamType `json:"type"`
 }
 
+// Parameters is just an array of Parameter.
+type Parameters []Parameter
+
 // NewParameter returns new parameter of specified name and type.
 func NewParameter(name string, typ smartcontract.ParamType) Parameter {
 	return Parameter{
@@ -54,3 +57,24 @@ func (p *Parameter) FromStackItem(item stackitem.Item) error {
 	}
 	return nil
 }
+
+// AreValid checks all parameters for validity and consistency.
+func (p Parameters) AreValid() error {
+	if len(p) < 2 {
+		return nil
+	}
+	names := make([]string, len(p))
+	for i := range p {
+		names[i] = p[i].Name
+	}
+	sort.Strings(names)
+	for i := range names {
+		if i == 0 {
+			continue
+		}
+		if names[i] == names[i-1] {
+			return errors.New("duplicate parameter name")
+		}
+	}
+	return nil
+}