engine: util: Improve StructTagToFieldName and add tests

This improves this function to make it more generic.

engine/util/util_test.go

@@ -21,6 +21,7 @@ package util
 
 import (
 	"os/user"
+	"reflect"
 	"strconv"
 	"testing"
 )
@@ -105,3 +106,61 @@ func TestCurrentUserGroupById(t *testing.T) {
 		t.Errorf("gid didn't match current user's: %s vs %s", strconv.Itoa(gid), currentGID)
 	}
 }
+
+func TestStructTagToFieldName0(t *testing.T) {
+	type foo struct {
+		A string `lang:"aaa"`
+		B bool   `lang:"bbb"`
+		C int64  `lang:"ccc"`
+	}
+	f := &foo{ // a ptr!
+		A: "hello",
+		B: true,
+		C: 13,
+	}
+	m, err := StructTagToFieldName(f) // (map[string]string, error)
+	if err != nil {
+		t.Errorf("got error: %+v", err)
+		return
+	}
+	t.Logf("got output: %+v", m)
+	expected := map[string]string{
+		"aaa": "A",
+		"bbb": "B",
+		"ccc": "C",
+	}
+	if !reflect.DeepEqual(m, expected) {
+		t.Errorf("unexpected result")
+		return
+	}
+}
+
+func TestStructTagToFieldName1(t *testing.T) {
+	type foo struct {
+		A string `lang:"aaa"`
+		B bool   `lang:"bbb"`
+		C int64  `lang:"ccc"`
+	}
+	f := foo{ // not a ptr!
+		A: "hello",
+		B: true,
+		C: 13,
+	}
+	m, err := StructTagToFieldName(f) // (map[string]string, error)
+	if err == nil {
+		t.Errorf("expected error, got nil")
+		//return
+	}
+	t.Logf("got output: %+v", m)
+	t.Logf("got error: %+v", err)
+}
+
+func TestStructTagToFieldName2(t *testing.T) {
+	m, err := StructTagToFieldName(nil) // (map[string]string, error)
+	if err == nil {
+		t.Errorf("expected error, got nil")
+		//return
+	}
+	t.Logf("got output: %+v", m)
+	t.Logf("got error: %+v", err)
+}