[fix] lock and disable convert for Call() func (#89)

* add call lock

* not convert

Author: hyorigo

call.go

@@ -9,6 +9,9 @@ import (
 
 // Call executes a Starlark function or builtin saved in the thread and returns the result.
 func (m *Machine) Call(name string, args ...interface{}) (out interface{}, err error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
 	defer func() {
 		if r := recover(); r != nil {
 			err = errorStarlarkPanic("call", r)
@@ -49,7 +52,12 @@ func (m *Machine) Call(name string, args ...interface{}) (out interface{}, err e
 
 	// call and convert result
 	res, err := starlark.Call(m.thread, callFunc, sl, nil)
-	out = convert.FromValue(res)
+	if m.enableOutConv { // convert to interface{} if enabled
+		out = convert.FromValue(res)
+	} else {
+		out = res
+	}
+	// handle error
 	if err != nil {
 		return out, errorStarlarkError("call", err)
 	}

call_test.go

@@ -212,3 +212,40 @@ def work(x):
 		})
 	}
 }
+
+func TestMachine_Call_Convert(t *testing.T) {
+	m := starlet.NewDefault()
+	m.SetCustomTag("json")
+	_, err := m.RunScript([]byte(`
+def work(x, y):
+	return x * y
+`), nil)
+	if err != nil {
+		t.Errorf("expected no error, got %v", err)
+		return
+	}
+
+	// call and check --- conversion is enabled by default
+	got, err := m.Call("work", 10, 20)
+	if err != nil {
+		t.Errorf("expected no error, got %v", err)
+		return
+	}
+	if got != int64(200) {
+		t.Errorf("expected 200, got %v", got)
+	}
+
+	// not convert
+	m.SetOutputConversionEnabled(false)
+	got, err = m.Call("work", 5, 6)
+	if err != nil {
+		t.Errorf("expected no error, got %v", err)
+		return
+	}
+	if v, ok := got.(starlark.Value); !ok {
+		t.Errorf("expected starlark Value, got %T", got)
+		return
+	} else if v != starlark.MakeInt(30) {
+		t.Errorf("got unexpected value: %v", v)
+	}
+}