Add nil checks to HTTP request validation dispatch (#44371)

Signed-off-by: Igor Suleymanov <igor.suleymanov@grafana.com>

pkg/web/binding.go

@@ -26,14 +26,27 @@ type Validator interface {
 }
 
 func validate(obj interface{}) error {
+	// First check if obj is nil, because we cannot validate those.
+	if obj == nil {
+		return nil
+	}
+
+	// Second, check if obj has a nil interface value.
+	// This is to prevent panics when obj is an instance of uninitialised struct pointer / interface.
+	t := reflect.TypeOf(obj)
+	v := reflect.ValueOf(obj)
+
+	if v.Kind() == reflect.Ptr && v.IsNil() {
+		return nil
+	}
+
 	// If type has a Validate() method - use that
 	if validator, ok := obj.(Validator); ok {
 		return validator.Validate()
 	}
+
 	// Otherwise, use reflection to match `binding:"Required"` struct field tags.
 	// Resolve all pointers and interfaces, until we get a concrete type.
-	t := reflect.TypeOf(obj)
-	v := reflect.ValueOf(obj)
 	for v.Kind() == reflect.Interface || v.Kind() == reflect.Ptr {
 		t = t.Elem()
 		v = v.Elem()

pkg/web/binding_test.go

@@ -50,8 +50,22 @@ func (sv StructWithValidation) Validate() error {
 	return nil
 }
 
+type StructWithPointerValidation struct {
+	A int
+}
+
+func (sv *StructWithPointerValidation) Validate() error {
+	if sv.A < 10 {
+		return errors.New("too small")
+	}
+	return nil
+}
+
 func TestValidationSuccess(t *testing.T) {
+	var nilInterface *StructWithPointerValidation
+
 	for _, x := range []interface{}{
+		nil,
 		42,
 		"foo",
 		struct{ A int }{},
@@ -65,6 +79,8 @@ func TestValidationSuccess(t *testing.T) {
 		StructWithStruct{StructWithInt{3}},
 		StructWithStructPointer{&StructWithInt{3}},
 		StructWithValidation{42},
+		&StructWithPointerValidation{42},
+		nilInterface,
 	} {
 		if err := validate(x); err != nil {
 			t.Error("Validation failed:", x, err)
@@ -93,6 +109,7 @@ func TestValidationFailure(t *testing.T) {
 		StructWithStructPointer{},
 		StructWithStructPointer{&StructWithInt{}},
 		StructWithValidation{2},
+		&StructWithPointerValidation{2},
 	} {
 		if err := validate(x); err == nil {
 			t.Error("Validation should fail:", i, x)