fix: handle invalid values in Decoder's decode method

common/structure/structure.go

@@ -86,7 +86,27 @@ func (d *Decoder) Decode(src map[string]any, dst any) error {
 	return nil
 }
 
+// isNil returns true if the input is nil or a typed nil pointer.
+func isNil(input any) bool {
+	if input == nil {
+		return true
+	}
+	val := reflect.ValueOf(input)
+	return val.Kind() == reflect.Pointer && val.IsNil()
+}
+
 func (d *Decoder) decode(name string, data any, val reflect.Value) error {
+	if isNil(data) {
+		// If the data is nil, then we don't set anything
+		// Maybe we should set to zero value?
+		return nil
+	}
+	if !reflect.ValueOf(data).IsValid() {
+		// If the input value is invalid, then we just set the value
+		// to be the zero value.
+		val.Set(reflect.Zero(val.Type()))
+		return nil
+	}
 	for {
 		kind := val.Kind()
 		if kind == reflect.Pointer && val.IsNil() {

common/structure/structure_test.go

@@ -267,3 +267,21 @@ func TestStructure_TextUnmarshaller(t *testing.T) {
 	err = decoder.Decode(rawMap, s)
 	assert.NotNilf(t, err, "should throw error: %#v", s)
 }
+
+func TestStructure_Null(t *testing.T) {
+	rawMap := map[string]any{
+		"opt": map[string]any{
+			"bar": nil,
+		},
+	}
+
+	s := struct {
+		Opt struct {
+			Bar string `test:"bar,optional"`
+		} `test:"opt,optional"`
+	}{}
+
+	err := decoder.Decode(rawMap, &s)
+	assert.Nil(t, err)
+	assert.Equal(t, s.Opt.Bar, "")
+}