fix(fcm): Allow for override of batch endpoint URL

messaging/messaging.go

@@ -32,8 +32,8 @@ import (
 )
 
 const (
-	messagingEndpoint = "https://fcm.googleapis.com/v1"
-	batchEndpoint     = "https://fcm.googleapis.com/batch"
+	defaultMessagingEndpoint = "https://fcm.googleapis.com/v1"
+	defaultBatchEndpoint     = "https://fcm.googleapis.com/batch"
 
 	firebaseClientHeader   = "X-Firebase-Client"
 	apiFormatVersionHeader = "X-GOOG-API-FORMAT-VERSION"
@@ -862,17 +862,20 @@ func NewClient(ctx context.Context, c *internal.MessagingConfig) (*Client, error
 		return nil, errors.New("project ID is required to access Firebase Cloud Messaging client")
 	}
 
-	hc, endpoint, err := transport.NewHTTPClient(ctx, c.Opts...)
+	hc, messagingEndpoint, err := transport.NewHTTPClient(ctx, c.Opts...)
 	if err != nil {
 		return nil, err
 	}
 
-	if endpoint == "" {
-		endpoint = messagingEndpoint
+	batchEndpoint := messagingEndpoint
+
+	if messagingEndpoint == "" {
+		messagingEndpoint = defaultMessagingEndpoint
+		batchEndpoint = defaultBatchEndpoint
 	}
 
 	return &Client{
-		fcmClient: newFCMClient(hc, c, endpoint),
+		fcmClient: newFCMClient(hc, c, messagingEndpoint, batchEndpoint),
 		iidClient: newIIDClient(hc),
 	}, nil
 }
@@ -885,7 +888,7 @@ type fcmClient struct {
 	httpClient    *internal.HTTPClient
 }
 
-func newFCMClient(hc *http.Client, conf *internal.MessagingConfig, endpoint string) *fcmClient {
+func newFCMClient(hc *http.Client, conf *internal.MessagingConfig, messagingEndpoint string, batchEndpoint string) *fcmClient {
 	client := internal.WithDefaultRetryConfig(hc)
 	client.CreateErrFn = handleFCMError
 
@@ -896,7 +899,7 @@ func newFCMClient(hc *http.Client, conf *internal.MessagingConfig, endpoint stri
 	}
 
 	return &fcmClient{
-		fcmEndpoint:   endpoint,
+		fcmEndpoint:   messagingEndpoint,
 		batchEndpoint: batchEndpoint,
 		project:       conf.ProjectID,
 		version:       version,

messaging/messaging_batch_test.go

@@ -27,6 +27,8 @@ import (
 	"net/http/httptest"
 	"net/textproto"
 	"testing"
+
+	"google.golang.org/api/option"
 )
 
 var testMessages = []*Message{
@@ -520,6 +522,46 @@ func TestSendMulticast(t *testing.T) {
 	}
 }
 
+func TestSendMulticastWithCustomEndpoint(t *testing.T) {
+	resp, err := createMultipartResponse(testSuccessResponse, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var req []byte
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		req, _ = ioutil.ReadAll(r.Body)
+		w.Header().Set("Content-Type", wantMime)
+		w.Write(resp)
+	}))
+	defer ts.Close()
+
+	ctx := context.Background()
+
+	conf := *testMessagingConfig
+	customBatchEndpoint := fmt.Sprintf("%s/v1", ts.URL)
+	optEndpoint := option.WithEndpoint(customBatchEndpoint)
+	conf.Opts = append(conf.Opts, optEndpoint)
+
+	client, err := NewClient(ctx, &conf)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if customBatchEndpoint != client.batchEndpoint {
+		t.Errorf("client.batchEndpoint = %q; want = %q", client.batchEndpoint, customBatchEndpoint)
+	}
+
+	br, err := client.SendMulticast(ctx, testMulticastMessage)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := checkSuccessfulBatchResponse(br, req, false); err != nil {
+		t.Errorf("SendMulticast() = %v", err)
+	}
+}
+
 func TestSendMulticastDryRun(t *testing.T) {
 	resp, err := createMultipartResponse(testSuccessResponse, nil)
 	if err != nil {