Fix DynamoDB string accessor type check

Author: kiwigitops

events/attributevalue.go

@@ -116,13 +116,13 @@ func (av DynamoDBAttributeValue) NumberSet() []string {
 // String provides access to an attribute of type String.
 // Method panics if the attribute is not of type String.
 func (av DynamoDBAttributeValue) String() string {
-	if av.dataType == DataTypeString {
-		return av.value.(string)
-	}
-	// If dataType is not DataTypeString during fmt.Sprintf("%#v", ...)
-	// compiler confuses with fmt.Stringer interface and panics
-	// instead of printing the struct.
-	return fmt.Sprintf("%v", dynamoDbAttributeValue(av))
+	av.ensureType(DataTypeString)
+	return av.value.(string)
+}
+
+// GoString formats the attribute value without calling the String accessor.
+func (av DynamoDBAttributeValue) GoString() string {
+	return fmt.Sprintf("%#v", dynamoDbAttributeValue(av))
 }
 
 // StringSet provides access to an attribute of type String Set.

events/attributevalue_test.go

@@ -5,6 +5,7 @@ package events
 import (
 	"encoding/base64"
 	"encoding/json"
+	"fmt"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -206,6 +207,7 @@ func TestAccessWithWrongTypePanics(t *testing.T) {
 		{`{ "N": "123.45"}`, func(av DynamoDBAttributeValue) { av.Boolean() }, IncompatibleDynamoDBTypeError{Requested: DataTypeBoolean, Actual: DataTypeNumber}},
 		{`{ "NS": ["1234", "567.8"] }`, func(av DynamoDBAttributeValue) { av.Boolean() }, IncompatibleDynamoDBTypeError{Requested: DataTypeBoolean, Actual: DataTypeNumberSet}},
 		{`{ "NULL": true}`, func(av DynamoDBAttributeValue) { av.Number() }, IncompatibleDynamoDBTypeError{Requested: DataTypeNumber, Actual: DataTypeNull}},
+		{`{ "BOOL": true}`, func(av DynamoDBAttributeValue) { av.String() }, IncompatibleDynamoDBTypeError{Requested: DataTypeString, Actual: DataTypeBoolean}},
 		{`{ "S": "Hello"}`, func(av DynamoDBAttributeValue) { av.Number() }, IncompatibleDynamoDBTypeError{Requested: DataTypeNumber, Actual: DataTypeString}},
 		{`{ "SS": [ "Giraffe", "Zebra" ] }`, func(av DynamoDBAttributeValue) { av.Number() }, IncompatibleDynamoDBTypeError{Requested: DataTypeNumber, Actual: DataTypeStringSet}},
 	}
@@ -219,6 +221,13 @@ func TestAccessWithWrongTypePanics(t *testing.T) {
 	}
 }
 
+func TestDynamoDBAttributeValueGoStringDoesNotCallStringAccessor(t *testing.T) {
+	var av DynamoDBAttributeValue
+	err := json.Unmarshal([]byte(`{ "BOOL": true}`), &av)
+	assert.Nil(t, err)
+	assert.NotPanics(t, func() { fmt.Sprintf("%#v", av) })
+}
+
 func TestMarshalAndUnmarshalString(t *testing.T) {
 	const inputString = "INPUT STRING"
 	inputValue := NewStringAttribute(inputString)