Add support for struct tag

pongo2_issues_test.go

@@ -43,3 +43,53 @@ func TestIssue297(t *testing.T) {
 		t.Fatalf("Expected `Testing: one two three four\nfive six!`, but got `%v`.", str)
 	}
 }
+
+type StructWithoutTag struct {
+	Name string
+	Age  int
+}
+
+type StructWithTag struct {
+	Name string `pongo2:"my_name"`
+	Age  int    `pongo2:"my_age"`
+}
+
+func TestIssue319StrutWithTag(t *testing.T) {
+	s := StructWithTag{
+		Name: "Andy Dufresne",
+		Age:  23,
+	}
+	ctx := pongo2.Context{
+		"mystruct": s,
+	}
+	template := `My name is {{ mystruct.my_name }}, age is {{ mystruct.my_age }}`
+	out, err := pongo2.FromString(template)
+	if err != nil {
+		t.Error(err)
+	}
+	execute, err := out.Execute(ctx)
+	if err != nil {
+		t.Error(err)
+	}
+	mustEqual(t, execute, "My name is Andy Dufresne, age is 23")
+}
+
+func TestIssue319StrutWithoutTag(t *testing.T) {
+	s := StructWithoutTag{
+		Name: "Andy Dufresne",
+		Age:  23,
+	}
+	ctx := pongo2.Context{
+		"mystruct": s,
+	}
+	template := `My name is {{ mystruct.Name }}, age is {{ mystruct.Age }}`
+	out, err := pongo2.FromString(template)
+	if err != nil {
+		t.Error(err)
+	}
+	execute, err := out.Execute(ctx)
+	if err != nil {
+		t.Error(err)
+	}
+	mustEqual(t, execute, "My name is Andy Dufresne, age is 23")
+}

variable.go

@@ -324,7 +324,24 @@ func (vr *variableResolver) resolve(ctx *ExecutionContext) (*Value, error) {
 					// Calling a field or key
 					switch current.Kind() {
 					case reflect.Struct:
-						current = current.FieldByName(part.s)
+						//save tag and field name into map
+						tagMap := make(map[string]string)
+						//get all tags of current struct
+						fields := current.NumField()
+						for i := 0; i < fields; i++ {
+							field := current.Type().Field(i)
+							tagMap[field.Tag.Get("pongo2")] = field.Name
+						}
+						//get all tags of current field
+						field := current.FieldByName(part.s)
+						if !field.IsValid() {
+							//if field is not valid, try to get field by tag
+							if tagMap[part.s] != "" {
+								current = current.FieldByName(tagMap[part.s])
+							}
+						} else {
+							current = field
+						}
 					case reflect.Map:
 						current = current.MapIndex(reflect.ValueOf(part.s))
 					default: