Fix typeless Update and Explain API

This commit will make the Update and Explain services to fall back to a
typeless update/explain URL in case the `type` is explicitly set to the
empty string.

See #1099

Author: olivere

explain.go

@@ -202,7 +202,7 @@ func (s *ExplainService) buildURL() (string, url.Values, error) {
 	var path string
 	var err error
 
-	if s.typ == "_doc" {
+	if s.typ == "" || s.typ == "_doc" {
 		path, err = uritemplates.Expand("/{index}/_explain/{id}", map[string]string{
 			"id":    s.id,
 			"index": s.index,

update.go

@@ -201,7 +201,7 @@ func (b *UpdateService) url() (string, url.Values, error) {
 	// Build url
 	var path string
 	var err error
-	if b.typ == "_doc" {
+	if b.typ == "" || b.typ == "_doc" {
 		path, err = uritemplates.Expand("/{index}/_update/{id}", map[string]string{
 			"index": b.index,
 			"id":    b.id,

update_integration_test.go

@@ -8,8 +8,60 @@ import (
 	"context"
 	"encoding/json"
 	"testing"
+	"time"
 )
 
+func TestUpdateWithDoc(t *testing.T) {
+	client := setupTestClientAndCreateIndexAndAddDocs(t) // , SetTraceLog(log.New(os.Stdout, "", 0)))
+
+	// Get original
+	getRes, err := client.Get().Index(testIndexName).Id("1").Do(context.TODO())
+	if err != nil {
+		t.Fatal(err)
+	}
+	var original tweet
+	if err := json.Unmarshal(getRes.Source, &original); err != nil {
+		t.Fatal(err)
+	}
+
+	// Partial update
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	updRes, err := client.Update().
+		Index(testIndexName).
+		Id("1").
+		Doc(map[string]interface{}{
+			"message": "Updated message text.",
+		}).
+		Do(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if updRes == nil {
+		t.Fatal("response is nil")
+	}
+	if want, have := "updated", updRes.Result; want != have {
+		t.Fatalf("want Result = %q, have %v", want, have)
+	}
+
+	// Get new version
+	getRes, err = client.Get().Index(testIndexName).Id("1").Do(context.TODO())
+	if err != nil {
+		t.Fatal(err)
+	}
+	var updated tweet
+	if err := json.Unmarshal(getRes.Source, &updated); err != nil {
+		t.Fatal(err)
+	}
+
+	if want, have := original.User, updated.User; want != have {
+		t.Fatalf("want User = %q, have %v", want, have)
+	}
+	if want, have := "Updated message text.", updated.Message; want != have {
+		t.Fatalf("want Message = %q, have %v", want, have)
+	}
+}
+
 func TestUpdateWithScript(t *testing.T) {
 	client := setupTestClientAndCreateIndexAndAddDocs(t) // , SetTraceLog(log.New(os.Stdout, "", 0)))