fix(transport/grpc): retain UserAgent option with new auth stack

transport/grpc/dial.go

@@ -53,6 +53,9 @@ var logRateLimiter = rate.Sometimes{Interval: 1 * time.Second}
 // Assign to var for unit test replacement
 var dialContext = grpc.DialContext
 
+// Assign to var for unit test replacement
+var dialContextNewAuth = grpctransport.Dial
+
 // otelStatsHandler is a singleton otelgrpc.clientHandler to be used across
 // all dial connections to avoid the memory leak documented in
 // https://github.com/open-telemetry/opentelemetry-go-contrib/issues/4226
@@ -218,12 +221,12 @@ func dialPoolNewAuth(ctx context.Context, secure bool, poolSize int, ds *interna
 		defaultEndpointTemplate = ds.DefaultEndpoint
 	}
 
-	pool, err := grpctransport.Dial(ctx, secure, &grpctransport.Options{
+	pool, err := dialContextNewAuth(ctx, secure, &grpctransport.Options{
 		DisableTelemetry:      ds.TelemetryDisabled,
 		DisableAuthentication: ds.NoAuth,
 		Endpoint:              ds.Endpoint,
 		Metadata:              metadata,
-		GRPCDialOpts:          ds.GRPCDialOpts,
+		GRPCDialOpts:          prepareDialOptsNewAuth(ds),
 		PoolSize:              poolSize,
 		Credentials:           creds,
 		APIKey:                ds.APIKey,
@@ -248,6 +251,15 @@ func dialPoolNewAuth(ctx context.Context, secure bool, poolSize int, ds *interna
 	return pool, err
 }
 
+func prepareDialOptsNewAuth(ds *internal.DialSettings) []grpc.DialOption {
+	var opts []grpc.DialOption
+	if ds.UserAgent != "" {
+		opts = append(opts, grpc.WithUserAgent(ds.UserAgent))
+	}
+
+	return append(opts, ds.GRPCDialOpts...)
+}
+
 func dial(ctx context.Context, insecure bool, o *internal.DialSettings) (*grpc.ClientConn, error) {
 	if o.HTTPClient != nil {
 		return nil, errors.New("unsupported HTTP client specified")

transport/grpc/dial_test.go

@@ -11,6 +11,7 @@ import (
 	"strings"
 	"testing"
 
+	"cloud.google.com/go/auth/grpctransport"
 	"cloud.google.com/go/compute/metadata"
 	"github.com/google/go-cmp/cmp"
 	"golang.org/x/oauth2/google"
@@ -35,6 +36,73 @@ func TestDial(t *testing.T) {
 	dial(context.Background(), false, &o)
 }
 
+func TestDialPoolNewAuthDialOptions(t *testing.T) {
+	oldDialContextNewAuth := dialContextNewAuth
+	var wantNumOpts int
+	// Replace package var in order to assert DialContext args.
+	dialContextNewAuth = func(ctx context.Context, secure bool, opts *grpctransport.Options) (grpctransport.GRPCClientConnPool, error) {
+		if len(opts.GRPCDialOpts) != wantNumOpts {
+			t.Fatalf("got: %d, want: %d", len(opts.GRPCDialOpts), wantNumOpts)
+		}
+		return nil, nil
+	}
+	defer func() {
+		dialContextNewAuth = oldDialContextNewAuth
+	}()
+
+	for _, testcase := range []struct {
+		name        string
+		ds          *internal.DialSettings
+		wantNumOpts int
+	}{
+		{
+			name:        "no dial options",
+			ds:          &internal.DialSettings{},
+			wantNumOpts: 0,
+		},
+		{
+			name: "with user agent",
+			ds: &internal.DialSettings{
+				UserAgent: "test",
+			},
+			wantNumOpts: 1,
+		},
+	} {
+		t.Run(testcase.name, func(t *testing.T) {
+			wantNumOpts = testcase.wantNumOpts
+			dialPoolNewAuth(context.Background(), false, 1, testcase.ds)
+		})
+	}
+}
+
+func TestPrepareDialOptsNewAuth(t *testing.T) {
+	for _, testcase := range []struct {
+		name        string
+		ds          *internal.DialSettings
+		wantNumOpts int
+	}{
+		{
+			name:        "empty",
+			ds:          &internal.DialSettings{},
+			wantNumOpts: 0,
+		},
+		{
+			name: "user agent",
+			ds: &internal.DialSettings{
+				UserAgent: "test",
+			},
+			wantNumOpts: 1,
+		},
+	} {
+		t.Run(testcase.name, func(t *testing.T) {
+			got := prepareDialOptsNewAuth(testcase.ds)
+			if len(got) != testcase.wantNumOpts {
+				t.Fatalf("got %d options, want %d options", len(got), testcase.wantNumOpts)
+			}
+		})
+	}
+}
+
 func TestCheckDirectPathEndPoint(t *testing.T) {
 	for _, testcase := range []struct {
 		name     string