Fix ES issue 28002 by a workaround

You can now pass `Lang("nil")` or `Lang("null")` in `Script` to set the
language to `null`. This is a workaround for [1] in ES <= 6.3. I will
remove this when 7.x is out.

[1] elastic/elasticsearch#28002
[2] elastic/elasticsearch#29039

Author: olivere

client.go

@@ -26,7 +26,7 @@ import (
 
 const (
 	// Version is the current version of Elastic.
-	Version = "6.1.20"
+	Version = "6.1.21"
 
 	// DefaultURL is the default endpoint of Elasticsearch on the local machine.
 	// It is used e.g. when initializing a new Client without a specific URL.

script.go

@@ -89,7 +89,10 @@ func (s *Script) Source() (interface{}, error) {
 	} else {
 		source["id"] = s.script
 	}
-	if s.lang != "" {
+	if s.lang == "null" || s.lang == "nil" {
+		// HACK(oe) Hotfix for https://github.com/elastic/elasticsearch/issues/28002; remove when 6.3 and/or 7.x are out.
+		source["lang"] = nil
+	} else if s.lang != "" {
 		source["lang"] = s.lang
 	}
 	if len(s.params) > 0 {

script_test.go

@@ -59,3 +59,23 @@ func TestScriptingStored(t *testing.T) {
 		t.Errorf("expected\n%s\n,got:\n%s", expected, got)
 	}
 }
+
+// TestScriptingBug28002 is a workaround for
+// https://github.com/elastic/elasticsearch/issues/28002
+// in that it allows to use a Script with ID but a language of "null".
+func TestScriptingBug28002(t *testing.T) {
+	builder := NewScriptStored("script-with-id").Lang("null").Param("factor", 2.0)
+	src, err := builder.Source()
+	if err != nil {
+		t.Fatal(err)
+	}
+	data, err := json.Marshal(src)
+	if err != nil {
+		t.Fatalf("marshaling to JSON failed: %v", err)
+	}
+	got := string(data)
+	expected := `{"id":"script-with-id","lang":null,"params":{"factor":2}}`
+	if got != expected {
+		t.Errorf("expected\n%s\n,got:\n%s", expected, got)
+	}
+}