fixes panic on GetArrayValueAt when OOB (#329)

Author: mvberg

examples/Issue328_test.go

@@ -0,0 +1,54 @@
+package examples
+
+import (
+	"testing"
+
+	"github.com/hyperjumptech/grule-rule-engine/ast"
+	"github.com/hyperjumptech/grule-rule-engine/builder"
+	"github.com/hyperjumptech/grule-rule-engine/engine"
+	"github.com/hyperjumptech/grule-rule-engine/pkg"
+	"github.com/stretchr/testify/assert"
+)
+
+const (
+	SliceOORRule = `
+		rule SliceOORRule {
+			when
+				PriceSlice.Prices[4] > 10 // will cause panic
+			then
+				Log("Price number 4 is greater than 10");
+				Retract("SliceOORRule");
+		}`
+)
+
+type AUserSliceIssue struct {
+	Prices []int
+}
+
+func TestMethodCall_SliceOOR(t *testing.T) {
+	ps := &AUserSliceIssue{
+		Prices: []int{1, 2, 3},
+	}
+
+	dataContext := ast.NewDataContext()
+	err := dataContext.Add("PriceSlice", ps)
+	assert.NoError(t, err)
+
+	// Prepare knowledgebase library and load it with our rule.
+	lib := ast.NewKnowledgeLibrary()
+	rb := builder.NewRuleBuilder(lib)
+	err = rb.BuildRuleFromResource("Test", "0.1.1", pkg.NewBytesResource([]byte(SliceOORRule)))
+	assert.NoError(t, err)
+
+	// expect no panic and no error (ReturnErrOnFailedRuleEvaluation = false)
+	eng1 := &engine.GruleEngine{MaxCycle: 5}
+	kb := lib.NewKnowledgeBaseInstance("Test", "0.1.1")
+	err = eng1.Execute(dataContext, kb)
+	assert.NoError(t, err)
+
+	// expect no panic and execute to return an error here
+	eng1 = &engine.GruleEngine{MaxCycle: 5, ReturnErrOnFailedRuleEvaluation: true}
+	kb = lib.NewKnowledgeBaseInstance("Test", "0.1.1")
+	err = eng1.Execute(dataContext, kb)
+	assert.Error(t, err)
+}

model/GoDataAccessLayer.go

@@ -16,8 +16,9 @@ package model
 
 import (
 	"fmt"
-	"github.com/hyperjumptech/grule-rule-engine/pkg"
 	"reflect"
+
+	"github.com/hyperjumptech/grule-rule-engine/pkg"
 )
 
 // NewGoValueNode creates new instance of ValueNode backed by golang reflection
@@ -96,9 +97,14 @@ func (node *GoValueNode) GetArrayType() (reflect.Type, error) {
 }
 
 // GetArrayValueAt to get the value of an array element if the current underlying value is an array
-func (node *GoValueNode) GetArrayValueAt(index int) (reflect.Value, error) {
+func (node *GoValueNode) GetArrayValueAt(index int) (val reflect.Value, err error) {
 	if node.IsArray() {
-		return node.thisValue.Index(index), nil
+		defer func() {
+			if r := recover(); r != nil {
+				err = fmt.Errorf("recovered : %v", r)
+			}
+		}()
+		return node.thisValue.Index(index), err
 	}
 	return reflect.Value{}, fmt.Errorf("this node identified as \"%s\" is not referring to an array or slice", node.IdentifiedAs())
 }
@@ -350,7 +356,7 @@ func (node *GoValueNode) CallFunction(funcName string, args ...reflect.Value) (r
 		case "Len":
 			strfunc = StrLen
 		case "MatchString":
-			strfunc = StrMatchRegexPattern	
+			strfunc = StrMatchRegexPattern
 		}
 		if strfunc != nil {
 			val, err := strfunc(node.thisValue.String(), args)